This work was supported by CIPER-Foundation for Science and Technology (FCT), Portugal (UID/DTP/00447/2019) and financed in part by the Coordena&#231;&#227;o de Aperfei&#231;oamento de Pessoal de N&#237;vel Superior - Brasil (CAPES) - Finance Code 001&#34;, and to the S&#227;o Paulo Research Foundation - FAPESP (PROCESS 2016/04544-3 and 2016/17735-1). Authors would like to thank Jo&#227;o Guilherme S. V. de Oliveira to the assistance in data sampling. M&#225;rio A. C. Espada acknowledge the financial support from IPDJ &#8211; Portuguese Institute of Sports and Youth.

Participants in the study from which the representative-subject data presented below were extracted20 (n = 11) were required to give their written informed consent prior to initiation of testing after the experimental procedures, associated risks and potential benefits of participation had been explained. The first visit comprised a familiarization session during which the swimmers were introduced to the concept of tethered swimming and the measurement techniques that would be in effect during the actual testing. An all-out tethered-swimming test was performed during the second visit and the rapidly incremented tethered-swimming protocol was performed on the third visit. Both tests were done in a semi-Olympic pool (25 m) with water temperature at 28 &#176;C.
1. Preparation of swimmer
<ol>
	<li>Instruct the swimmer to avoid strenuous exercise for 24 h preceding each testing session.</li>
	<li>Instruct the swimmer to arrive at the pool in a rested and fully hydrated state &#8805;3 h postprandial.</li>
	<li>Instruct the swimmer to refrain from ingesting stimulant beverages and alcohol for 24 h prior to each test.</li>
</ol>
2. All-out tethered-swimming test
<ol>
	<li>Prepare the 500 kg load cell that will be used to measure the highest force that the swimmer can exert during two trials comprising 30 s of all-out swimming21.
	<ol>
		<li>Open the N2000PRO Software (Power Din Pro - CEFISE) program on the computer.</li>
		<li>Open the Help Menu to verify the communication link between the computer and the load-cell analyzer.
		<ol>
			<li>Observe a green signal that indicates that the connection to the RS232 interface is well established.</li>
			<li>Set the countdown to start the test depending on circumstances.</li>
			<li>Set the sampling duration. Set the rest interval. Set the frames per second at 100 Hz.</li>
			<li>Set the unit of force measurement at N or kg depending on personal preference. Set the acquisition time in milliseconds.</li>
		</ol>
		</li>
		<li>Calibrate the load cell22 with 0 and 10 kg loads with the swimmer outside pool.</li>
		<li>Attach a load cell to the start block via the L-shaped flattened iron bar that is designed by CEFISE specifically for tethered-swimming measurements.</li>
		<li>Attach one end of the inelastic rope to the load cell and the other end to the swimmer by means of the custom-designed belt (CEFISE), which has ropes attached to both hips such that leg kicking will not interfere with the force measurement.</li>
	</ol>
	</li>
	<li>Prepare the swimmer for performance of the two-trial test.
	<ol>
		<li>Provide instructions to the swimmer regarding correct performance of all-out front-crawl swimming (e.g., prevent the head and trunk from rising while swimming as rapidly as possible, concentrate on kicking at a maximal rate in addition to maximal stroking, etc.).</li>
		<li>Instruct the swimmer to perform stretching and arm/leg swings at poolside in preparation.</li>
		<li>Instruct the swimmer to enter the pool and perform a standard warm-up protocol comprised of front-crawl swimming for 800 m at a light intensity with care taken to avoid engendering any lingering effects that could influence the results of the test.</li>
		<li>Allow the swimmer to exit the pool and rest at poolside for 10 min.</li>
		<li>Secure the belt around swimmer&#39;s waist. Attach the free end of the inelastic rope to the belt.</li>
		<li>Determine the load required to maintain the swimmer&#39;s body horizontally with a minimum amount of tension on the measurement system (loadbase).</li>
		<li>Signal the swimmer to begin Trial #1 of the test.</li>
	</ol>
	</li>
	<li>Monitor the swimmer during performance of the test.
	<ol>
		<li>Provide verbal encouragement to swimmer throughout 30 s test.</li>
		<li>Signal the swimmer to end the test. Detach the swimmer from the inelastic rope.</li>
		<li>Instruct the swimmer to perform a standard cool-down protocol comprised of front-crawl swimming at a light intensity.</li>
		<li>Allow the swimmer to rest for 30 min at poolside.</li>
		<li>Reattach the swimmer to the inelastic rope.</li>
		<li>Signal the swimmer to start Trial #2 of the test which is identical to Trial #1 (30 s of all-out swimming).</li>
		<li>Signal the swimmer to end the test.</li>
		<li>Instruct the swimmer to perform a standard cool-down protocol comprised of front-crawl swimming at a light intensity.</li>
		<li>Allow the swimmer to exit pool.</li>
	</ol>
	</li>
	<li>Analyze the data collected during the two-trial test.
	<ol>
		<li>Apply the smoothing process to the data using the N2000PRO software package23.</li>
		<li>Calculate the peaks of the wave-frequency signal from the force-time sinusoidal curve (range, sine 80&#176;-100&#176;) above loadbase for Trials #1 and 2.</li>
		<li>Define the averaged peaks of the force-time wave-frequency signal in the first 5 s and entire 30 s, respectively, as the peak force (Fpeak) and average force (Favg) for each trial.</li>
		<li>Use the higher values for Fpeak and Favg for further calculations.</li>
	</ol>
	</li>
</ol>
3. Incremental tethered-swimming test
<ol>
	<li>Calculate the loads that will be used to resist the swimmer&#39;s forward displacement during the incremental test.
	<ol>
		<li>Calculate the starting load as 30% of the Favg above loadbase.</li>
		<li>Calculate the increments to be applied per 60-s stage as 5% of Favg above loadbase.</li>
	</ol>
	</li>
	<li>Prepare the automated portable metabolic unit for data collection.
	<ol>
		<li>Open the unit&#39;s software.</li>
		<li>Verify the communication link between the computer and the automated portable metabolic unit.</li>
		<li>Power on unit and allow to warm up for 45 min. Ensure that batteries are fully charged.</li>
		<li>Perform calibration of unit for environmental air24.</li>
		<li>Perform calibration of unit for reference O2 (16%), CO2 (5%) and N (balance) concentrations24.</li>
		<li>Perform mask time-delay calibration24.</li>
		<li>Perform calibration of turbine with 3 L syringe24.</li>
		<li>Enter the subject data, ambient temperature and humidity.</li>
	</ol>
	</li>
	<li>Prepare the swimmer for performance of the incremental test.
	<ol>
		<li>Install a facemask and a snorkel on the swimmer.</li>
		<li>Instruct the swimmer to rest at poolside for 10 min to collect &#34;baseline&#34; gas exchange and ventilatory data.</li>
		<li>Instruct the swimmer to enter the pool and perform a standard warm-up protocol comprised of front-crawl swimming at a light intensity.</li>
		<li>Secure a belt around the swimmer&#39;s waist. Attach an inelastic rope to the belt with the other end of rope attached to the loading system.</li>
		<li>Instruct the swimmer that once the test begins to use the two markers on the bottom of the pool for reference points, which allow them to maintain a relatively-fixed position (e.g., &#177; 1 m from the desired position).</li>
		<li>Signal the swimmer to begin the test.</li>
	</ol>
	</li>
	<li>Monitor the swimmer during performance of the incremental test. 
	NOTE: A research assistant who is experienced in monitoring this type of testing should hold the gas-analysis unit at poolside being cognizant to do so without impeding swimmer displacement and/or elevating the swimmer&#39;s head.
	<ol>
		<li>Increase load while timing the 60 s stages.</li>
		<li>Terminate the test and record the time to limit of exercise tolerance when the swimmer is no longer able to maintain the requisite position despite strong verbal encouragement from the testers.</li>
		<li>Use the time to limit of exercise tolerance to calculate stages completed.</li>
		<li>Record loads for each stage and peak load.</li>
		<li>Detach the swimmer from the inelastic rope.</li>
		<li>Instruct the swimmer to perform a standard cool-down protocol comprised of front-crawl swimming at a low-to-moderate intensity.</li>
		<li>Allow the swimmer to exit the pool.</li>
	</ol>
	</li>
	<li>Analyze the data collected during the incremental test.
	<ol>
		<li>Smooth breath-by-breath gas-exchange data that were collected before and during test using the unit&#39;s software program.</li>
		<li>Export gas-exchange data in consecutive 9 s bin averages.</li>
		<li>Perform three-point rolling average on consecutive 9 s bin averages for V&#775;O2.</li>
		<li>Record highest three-point rolling-average value as the V&#775;O2peak.</li>
		<li>Using final three-point rolling-average value for each completed stage, calculate V&#775;O2-load relationship via linear regression. Exclude data from end stages of test if a V&#775;O2 plateau appears to be present (visual inspection).</li>
		<li>Using consecutive 9 s bin averages, determine V&#775;O2GET.
		<ol>
			<li>Determine the first disproportionate increase in the rate of CO2 production (V&#775;CO2) compared to V&#775;O2.</li>
			<li>Determine the increase in the ratio of the expired rate of ventilation (V&#775;E) to V&#775;O2 with no increase in the ratio of V&#775;E to V&#775;CO2.</li>
			<li>Determine the increase in end-tidal O2 tension with no fall in end-tidal CO2 tension.</li>
		</ol>
		</li>
		<li>Using consecutive 9-s bin averages, determine V&#775;O2RCP.
		<ol>
			<li>Determine the first disproportionate increase in V&#775;E compared to V&#775;CO2.</li>
			<li>Determine the decrease in end-tidal CO2.</li>
		</ol>
		</li>
		<li>Express V&#775;O2peak, V&#775;O2GET, V&#775;O2RCP and V&#775;O2-load slope in both absolute (L&#8729;min-1) and relative (to body mass; mL&#8729;min-1&#8729;kg-1) terms.</li>
		<li>Express V&#775;O2GET and V&#775;O2RCP in relative terms as a percentage of V&#775;O2peak.</li>
	</ol>
	</li>
</ol>

<ol>
	<li>Hill, A. V., Lupton, H. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Muscular+exercise,+lactic+acid,+and+the+supply+and+utilization+of+oxygen.">Muscular exercise, lactic acid, and the supply and utilization of oxygen.</a> Quarterly Journal of Medicine. 16 (62), 135-171 (1923).</li><li>Davis, H. A., Bassett, J., Hughes, P., Gass, G. C. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Anaerobic+threshold+and+lactate+turnpoint.">Anaerobic threshold and lactate turnpoint.</a> European Journal of Applied Physiology Occupational Physiology. 50 (3), 383-392 (1983).</li><li>Beaver, W. L., Wasserman, K., Whipp, B. J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=A+new+method+for+detecting+anaerobic+threshold+by+gas+exchange.">A new method for detecting anaerobic threshold by gas exchange.</a> Journal of Applied Physiology. 60 (6), 2020-2027 (1986).</li><li>Whipp, B. J., Wasserman, K. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Oxygen+uptake+kinetics+for+various+intensities+of+constant-load+work.">Oxygen uptake kinetics for various intensities of constant-load work.</a> Journal of Applied Physiology. 33 (3), 351-356 (1972).</li><li>Black, M. I., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Muscle+metabolic+and+neuromuscular+determinants+of+fatigue+during+cycling+in+different+exercise+intensity+domains.">Muscle metabolic and neuromuscular determinants of fatigue during cycling in different exercise intensity domains.</a> Journal of Applied Physiology. 122 (3), 446-459 (2017).</li><li>Whipp, B. J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Dynamics+of+pulmonary+gas+exchange.">Dynamics of pulmonary gas exchange.</a> Circulation. 76 (6 Pt 2), V118-V128 (1987).</li><li>Keir, D. A., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Exercise+Intensity+Thresholds:+Identifying+the+Boundaries+of+Sustainable+Performance.">Exercise Intensity Thresholds: Identifying the Boundaries of Sustainable Performance.</a> Medicine and Science in Sports and Exercise. 47 (9), 1932-1940 (2017).</li><li>Keir, D. A., Paterson, D. H., Kowalchuk, J. M., Murias, J. M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Using+ramp-incremental+VO2+responses+for+constant-intensity+exercise+selection.">Using ramp-incremental VO2 responses for constant-intensity exercise selection.</a> Applied Physiology, Nutrition and Metabolism. 43 (9), 882-892 (2018).</li><li>Iannetta, D., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=An+equation+to+predict+the+maximal+lactate+steady+state+from+ramp-incremental+exercise+test+data+in+cycling.">An equation to predict the maximal lactate steady state from ramp-incremental exercise test data in cycling.</a> Journal of Science and Medicine in Sport. 21 (12), 1274-1280 (2018).</li><li>Iannetta, D., Inglis, E. C., Fullerton, C., Passfield, L., Murias, J. M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Metabolic+and+performance-related+consequences+of+exercising+at+and+slightly+above+MLSS.">Metabolic and performance-related consequences of exercising at and slightly above MLSS.</a> Scandinavian Journal of Medicine &amp; Science in Sports. 28 (12), 2381 (2018).</li><li>DiMenna, F. J., Jones, A. M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term="Linear"+Versus+"Nonlinear"+VO2+Responses+to+Exercise:+Reshaping+Traditional+Beliefs.">"Linear" Versus "Nonlinear" VO2 Responses to Exercise: Reshaping Traditional Beliefs.</a> Journal of Exercise Science &amp; Fitness. 7 (2), 67-84 (2009).</li><li>Mitchell, J. H., Sproule, B. J., Chapman, C. B. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+physiological+meaning+of+the+maximal+oxygen+intake+test.">The physiological meaning of the maximal oxygen intake test.</a> Journal of Clinical Investigation. 37 (4), 538-547 (1958).</li><li>McArdle, W. D., Katch, F. I., Pechar, G. S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Comparison+of+continuous+and+discontinuous+treadmill+and+bicycle+tests+for+max+VO2.">Comparison of continuous and discontinuous treadmill and bicycle tests for max VO2.</a> Medicine and Science in Sports and Exercise. 5 (3), 156-160 (1973).</li><li>Whipp, B. J., Davis, J. A., Torres, F., Wasserman, K. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=A+test+to+determine+parameters+of+aerobic+function+during+exercise.">A test to determine parameters of aerobic function during exercise.</a> Journal of Applied Physiology: Respiratory Environmental and Exercise Physiology. 50 (1), 217-221 (1981).</li><li>Whipp, B. J., Davis, J. A., Wasserman, K. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Ventilatory+control+of+the+'isocapnic+buffering'+region+in+rapidly-incremental+exercise.">Ventilatory control of the 'isocapnic buffering' region in rapidly-incremental exercise.</a> Respiratory Physiology. 76 (3), 357-367 (1989).</li><li>Boone, J., Bourgois, J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+oxygen+uptake+response+to+incremental+ramp+exercise:+methodogical+and+physiological+issues.">The oxygen uptake response to incremental ramp exercise: methodogical and physiological issues.</a> Sports Medicine. 42 (6), 511-526 (2012).</li><li>Sousa, A., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Critical+evaluation+of+oxygen-uptake+assessment+in+swimming.">Critical evaluation of oxygen-uptake assessment in swimming.</a> International Journal of Sports Physiology and Performance. 9 (2), 190-202 (2014).</li><li>Fernandes, R. J., Sousa, M., Machado, L., Vilas-Boas, J. P. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Step+length+and+individual+anaerobic+threshold+assessment+in+swimming.">Step length and individual anaerobic threshold assessment in swimming.</a> International Journal of Sports Medicine. 32 (12), 940-946 (2011).</li><li>Ribeiro, J., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Metabolic+and+ventilatory+thresholds+assessment+in+front+crawl+swimming.">Metabolic and ventilatory thresholds assessment in front crawl swimming.</a> The Journal of Sports Medicine and Physical Fitness. 55 (7-8), 701-707 (2015).</li><li>Pess&#244;a Filho, D. M., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=A+rapidly+incremented+tethered-swimming+test+for+defining+domain-specific+training+zones.">A rapidly incremented tethered-swimming test for defining domain-specific training zones.</a> Journal of Human Kinetics. 57 (1), 117-128 (2017).</li><li>Dopsaj, M., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+relationship+between+50m-freestyle+results+and+characteristics+of+tethered+forces+in+male+sprint+swimmers:+A+new+approach+to+tethered+swimming+test.">The relationship between 50m-freestyle results and characteristics of tethered forces in male sprint swimmers: A new approach to tethered swimming test.</a> Physical Education &amp; Sport. 1 (7), 15-22 (2000).</li><li>Wheatley, C. M., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Conducting+Maximal+and+Submaximal+Endurance+Exercise+Testing+to+Measure+Physiological+and+Biological+Responses+to+Acute+Exercise+in+Humans.">Conducting Maximal and Submaximal Endurance Exercise Testing to Measure Physiological and Biological Responses to Acute Exercise in Humans.</a> Journal of Visualized Experiments. 17 (140), (2018).</li><li>Lansley, K. E., DiMenna, F. J., Bailey, S. J., Jones, A. M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=A+'new'+method+to+normalise+exercise+intensity.">A 'new' method to normalise exercise intensity.</a> International Journal of Sports Medicine. 32 (7), 535-541 (2011).</li><li>Iannetta, D., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=A+Critical+Evaluation+of+Current+Methods+for+Exercise+Prescription+in+Women+and+Men.">A Critical Evaluation of Current Methods for Exercise Prescription in Women and Men.</a> Medicine and Science in Sports and Exercise. , (2019).</li><li>Scharhag-Rosenberger, F., Meyer, T., G&#228;ssler, N., Faude, O., Kindermann, W. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Exercise+at+given+percentages+of+VO2max:+heterogeneous+metabolic+responses+between+individuals.">Exercise at given percentages of VO2max: heterogeneous metabolic responses between individuals.</a> Journal of Science and Medicine in Sport. 13 (1), 74-79 (2010).</li><li>Midgley, A. W., McNaughton, L. R., Jones, A. M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Training+to+enhance+the+physiological+determinants+of+long-distance+running+performance:+can+valid+recommendations+be+given+to+runners+and+coaches+based+on+current+scientific+knowledge?.">Training to enhance the physiological determinants of long-distance running performance: can valid recommendations be given to runners and coaches based on current scientific knowledge?.</a> Sports Medicine. 37 (10), 857-880 (2007).</li><li>Jones, A. M., DiMenna, F. J., Cardinale, M., Newton, R., Nosaka, K. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Cardiovascular+Assessment+and+Aerobic+Training+Prescription.">Cardiovascular Assessment and Aerobic Training Prescription.</a> Strength and Conditioning: Biological Principles and Practical Applications. , 291-304 (2011).</li><li>Beneke, R., von Duvillard, S. P. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Determination+of+maximal+lactate+steady+state+response+in+selected+sports+events.">Determination of maximal lactate steady state response in selected sports events.</a> Medicine and Science in Sports and Exercise. 28 (2), 241-246 (1996).</li><li>Beneke, R. M., H&#252;tler, M., Leith&#228;user, R. M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Maximal+lactate-steady-state+independent+of+performance.">Maximal lactate-steady-state independent of performance.</a> Medicine and Science in Sports and Exercise. 32 (6), 1135-1139 (2000).</li><li>Smith, C. G., Jones, A. M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+relationship+between+critical+velocity,+maximal+lactate+steady-state+velocity+and+lactate+turnpoint+velocity+in+runners.">The relationship between critical velocity, maximal lactate steady-state velocity and lactate turnpoint velocity in runners.</a> European Journal of Applied Physiology. 85 (1-2), 19-26 (2001).</li><li>Pringle, J. S., Jones, A. M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Maximal+lactate+steady+state,+critical+power+and+EMG+during+cycling.">Maximal lactate steady state, critical power and EMG during cycling.</a> European Journal of Applied Physiology. 88 (3), 214-226 (2002).</li><li>Mattioni Maturana, F., Keir, D. A., McLay, K. M., Murias, J. M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Can+measures+of+critical+power+precisely+estimate+the+maximal+metabolic+steady-state?.">Can measures of critical power precisely estimate the maximal metabolic steady-state?.</a> Applied Physiology Nutrition and Metabolism. 41 (11), 1197-1203 (2013).</li><li>Jones, A. M., Burnley, M., Black, M. I., Poole, D. C., Vanhatalo, A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+maximal+metabolic+steady+state:+redefining+the+'gold+standard'.">The maximal metabolic steady state: redefining the 'gold standard'.</a> Physiological Reports. 7 (10), e14098 (2018).</li><li>Scheuermann, B. W., Kowalchuk, J. M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Attenuated+respiratory+compensation+during+rapidly+incremented+ramp+exercise.">Attenuated respiratory compensation during rapidly incremented ramp exercise.</a> Respiratory Physiology. 114 (3), 227-238 (1998).</li><li>Morgan, D. W., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Variation+in+the+aerobic+demand+of+running+among+trained+and+untrained+subjects.">Variation in the aerobic demand of running among trained and untrained subjects.</a> Medicine and Science in Sports and Exercise. 27 (3), 404-409 (1995).</li><li>Franch, J., Madsen, K., Djurhuus, M. S., Pedersen, P. K. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Improved+running+economy+following+intensified+training+correlates+with+reduced+ventilatory+demands.">Improved running economy following intensified training correlates with reduced ventilatory demands.</a> Medicine and Science in Sports and Exercise. 30 (8), 1250-1256 (1998).</li><li>Holmer, I., Lundin, A., Eriksson, B. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Maximum+oxygen+uptake+during+swimming+and+running+by+elite+swimmers.">Maximum oxygen uptake during swimming and running by elite swimmers.</a> Journal of Applied Physiology. 36 (6), 711-714 (1974).</li><li>Bonen, A., Wilson, B. A., Yarkony, M., Belcastro, A. N. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Maximal+oxygen+uptake+during+free,+tethered,+and+flume+swimming.">Maximal oxygen uptake during free, tethered, and flume swimming.</a> Journal of Applied Physiology: Respiratory, Environmental and Exercise Physiology. 48 (2), 232-235 (1980).</li><li>Magel, J. R., Faulkner, J. A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Maximum+oxygen+uptakes+of+college+swimmers.">Maximum oxygen uptakes of college swimmers.</a> Journal of Applied Physiology. 22 (5), 929-933 (1967).</li><li>Poole, D. C., Jones, A. M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Measurement+of+the+maximum+oxygen+uptake+VO2max:+VO2peak+is+no+longer+acceptable.">Measurement of the maximum oxygen uptake VO2max: VO2peak is no longer acceptable.</a> Journal of Applied Physiology. 122 (4), 997-1002 (2017).</li></ol>

The authors have no disclosures to report.

An exercise challenge that involves enduring an incremental increase in WR until Tlim is reached is a standard testing protocol for assessment of endurance athletes. When such a test is performed with gradual, but rapid incrementation, it is particularly useful because in addition to the V&#775;O2max, gas exchange and ventilatory data collected during the test can be used to distinguish the region bounded by GET and RCP where acidosis is present, but arterial partial pressure of CO2 (PaCO...

An exercise test that involves an incremental increase in work rate (WR) from low to maximal (i.e., incremental exercise test; INC) provides the gold standard method of cardiorespiratory assessment for endurance athletes. In addition to the highest WR that the athlete can achieve (WRpeak), INC also allows for determination of the highest rate at which the individual can consume oxygen (O2) for that form of exercise (V&#775;O2peak) if gas exchange and ventilatory data are collected during the test1. The V&#775;O2peak represents the criterion measure of cardiorespiratory fitness. Moreover, analysis of gas exchange and ventilatory data collected as WR is increased provides a non-invasive way to identify the point at which blood-lactate concentration (blood [lactate]) increases above the baseline value (lactate threshold) and the point at which it begins to accumulate at an accelerated rate (lactate turnpoint)2. These metabolic breakpoints are estimated by determining the gas-exchange threshold (GET) and respiratory-compensation point (RCP), respectively3. Importantly, the GET provides a robust estimate of the point at which blood [lactate] initially increases whereas the &#34;hyperventilation&#34; that characterizes RCP is a more complex phenomenon that can be initiated by afferent input other than chemoreception per se. Consequently, conclusions based on identification of RCP should be made with caution.
When exercise is maintained at a constant rate of work (CWR), there are markedly different physiological response profiles based on the &#34;exercise-intensity domain&#34; within which the WR falls4,5. Specifically, achievement of a V&#775;O2 and blood [lactate] &#34;steady state&#34; is rapid in the moderate domain, delayed in the heavy domain and unattainable in the severe domain4,5. It is well established that the rate at which O2 can be consumed at GET during INC (V&#775;O2GET) serves as the metabolic rate that separates the moderate from heavy domain during CWR3,6. Although controversial, a number of recent observations indicate similar equivalence between the rate at which O2 can be consumed at RCP (V&#775;O2RCP) and heavy/severe separation7,8,9,10. Identification of V&#775;O2GET and V&#775;O2RCP from data collected during INC might, therefore, be useful for prescribing domain-specific training regimens for endurance athletes via metabolic rate with the caveat that aligning a metabolic rate with a specific work rate is more complex than simply doing so according to the V&#775;O2-work rate relationship derived from the incremental test8,11.
When the concept of testing to determine V&#775;O2max was initially explored, researchers had subjects perform bouts of track running to the limit of exercise tolerance (Tlim) at increasing speeds on separate days1. Research followed which confirmed that V&#775;O2max can also be determined from similar bouts performed to Tlim on the same day with rest periods interspersed12. Eventually, it was shown that a continuous protocol with WR increased in an incremental manner at specific time intervals (e.g., every 3 min) revealed the same V&#775;O2peak as the discontinuous tests13. Consequently, these &#34;graded exercise tests&#34; became the standard for determining this criterion measure of cardiorespiratory fitness. However, in 1981, Whipp and colleagues published research that indicated that for the purpose of V&#775;O2max measurement, INC could also be performed entirely in the non-steady state; that is, with WR increasing continuously as a &#34;smooth function of time&#34; (RAMP-INC)14. Unlike INC with extended stages and relatively large WR increases per stage, the gradual increase during RAMP-INC ensures that the &#34;isocapnic buffering region&#34; that separates GET and RCP will be clearly defined15. Furthermore, much like INC with stages, RAMP-INC can be used to assess &#34;exercise economy&#34; (i.e., the V&#775;O2 required per given WR); however, unlike INC with stages, in this case, it is the inverse of &#34;delta efficiency&#34; (i.e., the slope of the V&#775;O2-WR relationship) that is used for this purpose11 with consideration given to the fact that due to the complexities of the V&#775;O2 response to work rates across the intensity spectrum, this parameter will not be an immutable feature of INC per se (e.g., RAMP-INC initiated from different baseline work rates or characterized by different ramp slopes) or CWR exercise16.
For general fitness testing, INC is usually performed on a leg ergometer or treadmill because these modalities are more available and leg cycling and walking/running are familiar to the average person. Moreover, administration of RAMP-INC requires the ability to increase WR continuously in small increments (e.g., 1 W every 2 s); hence, an ergometer (typically leg cycling) is best suited for this type of testing. However, athlete assessment is more complex because athletes must be tested while performing the specific mode of exercise required for their sport. For cyclists and individuals who participate in sports that involve running, this is not problematic because of the accessibility and applicability of the aforementioned testing machines. Conversely, ecologically-valid testing with gas exchange and ventilatory data collection and the gradual WR incrementation required for RAMP-INC is more challenging when assessing aquatic athletes.
Prior to the advent of automated collection systems, gas-exchange assessment of swimmers was often performed using Douglas-bag collection following a maximal swim17. Once automated systems were developed, &#34;real-time&#34; collection took place, but not under &#34;real-swimming&#34; conditions (e.g., while swimmers swam in a flume which controlled WR)17. Unfortunately, the former method has inherent limitations due to the assumptions of &#34;backward extrapolation&#34; while the latter raises concerns regarding the degree to which flume swimming changes technique17. The current state of the art involves the use of portable breath-by-breath collection systems which move with the swimmer alongside the pool during free swimming17. While this type of measurement improves ecological validity, gradual WR incrementation is challenging. Indeed, INC during free swimming typically involves intervals of set distance (e.g., 200 m) at progressively-increasing velocities14,15. This means that a test consists of lengthy stages with large unequal WR increments. It is, therefore, not surprising that only a single metabolic breakpoint (typically called the &#34;anaerobic threshold&#34;) is reported by researchers who employ this test18,19. Instead, we have recently shown that both V&#775;O2GET and V&#775;O2RCP can be determined from data collected while swimmers performed stationary swimming in a pool against a load that was increased gradually and rapidly (i.e., incremental tethered swimming)20. While the unique breathing pattern that is present during swimming might render the aforementioned breakpoints harder to identify compared to typical modes of assessment (personal observation), we believe that this method of testing might be suitable as a &#34;swim ergometer&#34; that can be used for cardiorespiratory assessment of swimmers in a manner similar to how a stationary cycle is used for cyclists. Indeed, we have shown that V&#775;O2GET, V&#775;O2RCP and exercise economy (as indicated by the V&#775;O2-load slope) can all be determined from the rapidly incremented tethered-swimming protocol that is described below20.

<table><tbody><tr><td>3-L syringe</td><td>Hans Rudolph</td><td></td><td>Calibration device</td></tr><tr><td>Aquatrainer</td><td>COSMED</td><td></td><td>Snorkel system/gas-exchange measurement</td></tr><tr><td>K4b2</td><td>COSMED</td><td></td><td>Portable CPET unit/gas-exchange measurement</td></tr><tr><td>N200PRO</td><td>Cefise</td><td></td><td>Software program for analysis of force signal</td></tr><tr><td>Pacer 2 Swim</td><td>Kulzer TEC</td><td></td><td>Swimming velocity management/underwater LED line</td></tr><tr><td>Tether-system</td><td>Own design</td><td></td><td>Pulley-Rope system/loading management</td></tr><tr><td>Tether attachment</td><td>CEFISE</td><td></td><td>Bracket for attachment to swimmer</td></tr></tbody></table>

a rapidly incremented tethered-swimming maximal protocol for cardiorespiratory assessment of swimmers

Incremental exercise testing is the standard means of assessing cardiorespiratory capacity of endurance athletes. While the maximal rate of oxygen consumption is typically used as the criterion measurement in this regard, two metabolic breakpoints that reflect changes in the dynamics of lactate production/consumption as the work rate is increased are perhaps more relevant for endurance athletes from a functional standpoint. Exercise economy, which represents the rate of oxygen consumption relative to performance of submaximal work, is also an important parameter to measure for endurance-athlete assessment. Ramp incremental tests comprising a gradual but rapid increase in work rate until the limit of exercise tolerance is reached are useful for determining these parameters. This type of test is typically performed on a cycle ergometer or treadmill because there is a need for precision with respect to work-rate incrementation. However, athletes should be tested while performing the mode of exercise required for their sport. Consequently, swimmers are typically assessed during free-swimming incremental tests where such precision is difficult to achieve. We have recently suggested that stationary swimming against a load that is progressively increased (incremental tethered swimming) can serve as a &#34;swim ergometer&#34; by allowing sufficient precision to accommodate a gradual but rapid loading pattern that reveals the aforementioned metabolic breakpoints and exercise economy. However, the degree to which the peak rate of oxygen consumption achieved during such a protocol approximates the maximal rate that is measured during free swimming remains to be determined. In the present article, we explain how this rapidly incremented tethered-swimming protocol can be employed to assess the cardiorespiratory capacity of a swimmer. Specifically, we explain how assessment of a short-distance competitive swimmer using this protocol revealed that his rate of oxygen uptake was 30.3 and 34.8 mL&#8729;min-1&#8729;kg-1BM at his gas-exchange threshold and respiratory compensation point, respectively.

The data presented in Table 1 and depicted in Figures 1-4 represents the response profiles observed for a male swimmer (age, 24 years). At the time of data collection, the swimmer had been training for competitive swimming for 7 years. His specialty was short-distance (i.e., 50 m and 100 m) freestyle events.
The initial load on INC was set at a load that exceeded that which was required for this...

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A Rapidly Incremented Tethered-Swimming Maximal Protocol for Cardiorespiratory Assessment of Swimmers

As opposed to measurement during free swimming, which presents inherent challenges and limitations, determination of important parameters of cardiorespiratory function for swimmers can be made using a more feasible and easier to administer tethered-swimming rapidly incremented protocol with gas exchange and ventilatory data collection.

Incremental exercise testing is the standard means of assessing cardiorespiratory capacity of endurance athletes. While the maximal rate of oxygen ...

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Research

JoVE Journal

Biochemistry

8.8K Views.  São Paulo State University (UNESP) at Bauru. Tijdens stationair zwemmen tegen een toenemende belasting kunnen de gasuitwisselingsdrempel en het ademhalingscompensatiepunt gemakkelijk worden onderscheiden, twee belangrijke parameters om tijdens het vrije zwemmen met toenemende snelheid te meten. Intensiteitsprogressie via belastingsverhogingen tijdens incrementele oefening kan symmetrisch, geleidelijk en snel zijn tijdens vastgemaakt zwemmen, wat niet het geval is tijdens incrementeel vrij zwemmen met een toenemende snelheid. Het beheer ...

Video: A Rapidly Incremented Tethered-Swimming Maximal Protocol for Cardiorespiratory Assessment of Swimmers

Using Continuous Data Tracking Technology to Study Exercise Adherence in Pulmonary Rehabilitation

Pulmonary rehabilitation (PR) is an important component in the management of respiratory diseases. The effectiveness of PR is dependent upon adherence to exercise training recommendations. The study of exercise adherence is thus a key step towards the optimization of PR programs. To date, mostly indirect measures, such as rates of participation, completion, and attendance, have been used to determine adherence to PR. The purpose of the present protocol is to describe how continuous data tracking technology can be used to measure adherence to a prescribed aerobic training intensity on a second-by-second basis.
In our investigations, adherence has been defined as the percent time spent within a specified target heart rate range. As such, using a combination of hardware and software, heart rate is measured, tracked, and recorded during cycling second-by-second for each participant, for each exercise session. Using statistical software, the data is subsequently extracted and analyzed. The same protocol can be applied to determine adherence to other measures of exercise intensity, such as time spent at a specified wattage, level, or speed on the cycle ergometer. Furthermore, the hardware and software is also available to measure adherence to other modes of training, such as the treadmill, elliptical, stepper, and arm ergometer. The present protocol, therefore, has a vast applicability to directly measure adherence to aerobic exercise.

Pulmonary rehabilitation is widely recognized in the management of respiratory diseases. A key component to successful pulmonary rehabilitation is adherence to the recommended exercise training. The purpose of the present protocol is to describe how continuous data tracking technology can be used to precisely measure adherence to a prescribed aerobic training intensity.

Pulmonary rehabilitation (PR) is an important component in the management of respiratory diseases. The effectiveness of PR is dependent upon adherence to ...

Medicine

Swimming Performance Assessment in Fishes

Swimming performance tests of fish have been integral to studies of muscle energetics, swimming mechanics, gas exchange, cardiac physiology, disease, pollution, hypoxia and temperature. This paper describes a flexible protocol to assess fish swimming performance using equipment in which water velocity can be controlled. The protocol involves one to several stepped increases in flow speed that are intended to cause fish to fatigue. Step speeds and their duration can be set to capture swimming abilities of different physiological and ecological relevance. Most frequently step size is set to determine critical swimming velocity (Ucrit), which is intended to capture maximum sustained swimming ability. Traditionally this test has consisted of approximately ten steps each of 20 min duration. However, steps of shorter duration (e.g. 1 min) are increasingly being utilized to capture acceleration ability or burst swimming performance. Regardless of step size, swimming tests can be repeated over time to gauge individual variation and recovery ability. Endpoints related to swimming such as measures of metabolic rate, fin use, ventilation rate, and of behavior, such as the distance between schooling fish, are often included before, during and after swimming tests. Given the diversity of fish species, the number of unexplored research questions, and the importance of many species to global ecology and economic health, studies of fish swimming performance will remain popular and invaluable for the foreseeable future.

The lives of the majority of fish are predicated on swimming. This protocol describes techniques for capturing a range of swimming modes available to individual and schooling fish, and includes metrics associated with swimming physiology and behaviour.

Swimming performance tests of fish have been integral to studies of muscle energetics, swimming mechanics, gas exchange, cardiac physiology, disease, ...

Biology

Surgical Placement of Catheters for Long-term Cardiovascular Exercise Testing in Swine

This protocol describes the surgical procedure to chronically instrument swine and the procedure to exercise swine on a motor-driven treadmill. Early cardiopulmonary dysfunction is difficult to diagnose, particularly in animal models, as cardiopulmonary function is often measured invasively, requiring anesthesia. As many anesthetic agents are cardiodepressive, subtle changes in cardiovascular function may be masked. In contrast, chronic instrumentation allows for measurement of cardiopulmonary function in the awake state, so that measurements can be obtained under quiet resting conditions, without the effects of anesthesia and acute surgical trauma. Furthermore, when animals are properly trained, measurements can also be obtained during graded treadmill exercise.
Flow probes are placed around the aorta or pulmonary artery for measurement of cardiac output and around the left anterior descending coronary artery for measurement of coronary blood flow. Fluid-filled catheters are implanted in the aorta, pulmonary artery, left atrium, left ventricle and right ventricle for pressure measurement and blood sampling. In addition, a 20 G&#160;catheter is positioned in the anterior interventricular vein to allow coronary venous blood sampling.
After a week of recovery, swine are placed on a motor-driven treadmill, the catheters are connected to pressure and flow meters, and swine are subjected to a five-stage progressive exercise protocol, with each stage lasting 3 min. Hemodynamic signals are continuously recorded and blood samples are taken during the last 30 sec of each exercise stage.
The major advantage of studying chronically instrumented animals is that it allows serial assessment of cardiopulmonary function, not only at rest but also during physical stress such as exercise. Moreover, cardiopulmonary function can be assessed repeatedly during disease development and during chronic treatment, thereby increasing statistical power and hence limiting the number of animals required for a study.

Here we present a protocol to assess cardiopulmonary function in awake swine, at rest and during graded treadmill exercise. Chronic instrumentation allows for repeated hemodynamic measurements uninfluenced by cardiodepressive anesthetic agents.

This protocol describes the surgical procedure to chronically instrument swine and the procedure to exercise swine on a motor-driven treadmill. Early ...

Assessment of Pulmonary Capillary Blood Volume, Membrane Diffusing Capacity, and Intrapulmonary Arteriovenous Anastomoses During Exercise

Exercise is a stress to the pulmonary vasculature. With incremental exercise, the pulmonary diffusing capacity (DLCO) must increase to meet the increased oxygen demand; otherwise, a diffusion limitation may occur. The increase in DLCO with exercise is due to increased capillary blood volume (Vc) and membrane diffusing capacity (Dm). Vc and Dm increase secondary to the recruitment and distension of pulmonary capillaries, increasing the surface area for gas exchange and decreasing pulmonary vascular resistance, thereby attenuating the increase in pulmonary arterial pressure. At the same time, the recruitment of intrapulmonary arteriovenous anastomoses (IPAVA) during exercise may contribute to gas exchange impairment and/or prevent large increases in pulmonary artery pressure.
We describe two techniques to evaluate pulmonary diffusion and circulation at rest and during exercise. The first technique uses multiple-fraction of inspired oxygen (FIO2) DLCO breath holds to determine Vc and Dm at rest and during exercise. Additionally, echocardiography with intravenous agitated saline contrast is used to assess IPAVAs recruitment.
Representative data showed that the DLCO, Vc, and Dm increased with exercise intensity. Echocardiographic data showed no IPAVA recruitment at rest, while contrast bubbles were seen in the left ventricle with exercise, suggesting exercise-induced IPAVA recruitment.
The evaluation of pulmonary capillary blood volume, membrane diffusing capacity, and IPAVA recruitment using echocardiographic methods is useful to characterize the ability of the lung vasculature to adapt to the stress of exercise in health as well as in diseased groups, such as those with pulmonary arterial hypertension and chronic obstructive pulmonary disease.

To assess the pulmonary diffusion and vasculature responses to exercise, we describe the multiple-inspired oxygen diffusion capacity technique to determine capillary blood volume and membrane diffusing capacity, as well as agitated saline contrast echocardiography to assess the recruitment of intrapulmonary arteriovenous anastomoses.

Exercise is a stress to the pulmonary vasculature. With incremental exercise, the pulmonary diffusing capacity (DLCO) must increase to meet the increased ...

Conducting Maximal and Submaximal Endurance Exercise Testing to Measure Physiological and Biological Responses to Acute Exercise in Humans

Regular physical activity has a positive effect on human health, but the mechanisms controlling these effects remain unclear. The physiologic and biologic responses to acute exercise are predominantly influenced by the duration and intensity of the exercise regimen. As exercise is increasingly thought of as a therapeutic treatment and/or diagnostic tool, it is important that standardizable methodologies be utilized to understand the variability and to increase the reproducibility of exercise outputs and measurements of responses to such regimens. To that end, we describe two different cycling exercise regimens that yield different physiologic outputs. In a maximal exercise test, exercise intensity is continually increased with a greater workload resulting in an increasing cardiopulmonary and metabolic response (heart rate, stroke volume, ventilation, oxygen consumption and carbon dioxide production). In contrast, during endurance exercise tests, the demand is increased from that at rest, but is raised to a fixed submaximal exercise intensity resulting in a cardiopulmonary and metabolic response that typically plateaus. Along with the protocols, we provide suggestions on measuring physiologic outputs that include, but are not limited to, heart rate, slow and forced vital capacity, gas exchange metrics, and blood pressure to enable the comparison of exercise outputs between studies. Biospecimens can then be sampled to assess cellular, protein, and/or gene expression responses. Overall, this approach can be easily adapted into both short- and long-term effects of two distinct exercise regimens.

To assess the influence of exercise intensity on physiologic and biologic responses, two different exercise testing protocols were utilized. Methods outlining exercise testing on a cycle ergometer as an incremental maximal oxygen consumption test and endurance, steady state submaximal endurance test are described.

Regular physical activity has a positive effect on human health, but the mechanisms controlling these effects remain unclear. The physiologic and biologic ...

Integration of Brain Tissue Saturation Monitoring in Cardiopulmonary Exercise Testing in Patients with Heart Failure

Cerebral hypo-oxygenation during rest or exercise negatively impacts the exercise capacity of patients with heart failure with reduced ejection fraction (HF). However, in clinical cardiopulmonary exercise testing (CPET), cerebral hemodynamics is not assessed. NIRS is used to measure cerebral tissue oxygen saturation (SctO2) in the frontal lobe. This method is reliable and valid and has been utilized in several studies. SctO2 is lower during both rest and peak exercise in patients with HF than in healthy controls (66.3 &#177; 13.3% and 63.4 &#177; 13.8% vs. 73.1 &#177; 2.8% and 72 &#177; 3.2%). SctO2 at rest is significantly linearly correlated with peak VO2 (r = 0.602), oxygen uptake efficiency slope (r = 0.501), and brain natriuretic peptide (r = -0.492), all of which are recognized prognostic and disease severity markers, indicating its potential prognostic value. SctO2 is determined mainly by end-tidal CO2 pressure, mean arterial pressure, and hemoglobin in the HF population. This article demonstrates a protocol that integrates SctO2 using NIRS into incremental CPET on a calibrated bicycle ergometer.

This protocol integrated near-infrared spectroscopy into conventional cardiopulmonary exercise testing to identify the involvement of the cerebral hemodynamic response in exercise intolerance in patients with heart failure.

Cerebral hypo-oxygenation during rest or exercise negatively impacts the exercise capacity of patients with heart failure with reduced ejection fraction ...

Standardized Model of Ventricular Fibrillation and Advanced Cardiac Life Support in Swine

Cardiopulmonary resuscitation after cardiac arrest, independent of its origin, is a regularly encountered medical emergency in hospitals as well as preclinical settings. Prospective randomized trials in human subjects are difficult to design and ethically ambiguous, which results in a lack of evidence-based therapies. The model presented in this report represents one of the most common causes of cardiac arrests, ventricular fibrillation, in a standardized setting in a large animal model. This allows for reproducible observations and various therapeutic interventions under clinically accurate conditions, hence facilitating the generation of better evidence and eventually the potential for improved medical treatment.

Cardiopulmonary resuscitation and defibrillation are the only effective therapeutic options during cardiac arrest caused by ventricular fibrillation. This model presents a standardized regimen to induce, assess, and treat this physiological state in a porcine model, thus providing a clinical approach with various opportunities for data collection and analysis.

Cardiopulmonary resuscitation after cardiac arrest, independent of its origin, is a regularly encountered medical emergency in hospitals as well as ...

Assessment of Swim Endurance and Swim Behavior in Adult Zebrafish

Due to their renowned regenerative capacity, adult zebrafish are a premier vertebrate model to interrogate mechanisms of innate spinal cord regeneration. Following complete transection of their spinal cord, zebrafish extend glial and axonal bridges across severed tissue, regenerate neurons proximal to the lesion, and regain their swim capacities within 8 weeks of injury. Recovery of swim function is thus a central readout for functional spinal cord repair. Here, we describe a set of behavioral assays to quantify zebrafish motor capacity inside an enclosed swim tunnel. The goal of these methods is to provide quantifiable measurements of swim endurance and swim behavior in adult zebrafish. For swim endurance, zebrafish are subjected to a constantly increasing water current velocity until exhaustion, and time at exhaustion is reported. For swim behavior assessment, zebrafish are subjected to low current velocities and swim videos are captured with a dorsal view of the fish. Percent activity, burst frequency, and time spent against the water current provide quantifiable readouts of swim behavior. We quantified swim endurance and swim behavior in wild-type zebrafish before injury and after spinal cord transection. We found that zebrafish lose swim function after spinal cord transection and gradually regain that capacity between 2 and 6 weeks post-injury. The methods described in this study could be applied to neurobehavioral, musculoskeletal, skeletal muscle regeneration, and neural regeneration studies in adult zebrafish.

Capable of functional recovery after spinal cord injury, adult zebrafish is a premier model system to elucidate innate mechanisms of neural regeneration. Here, we describe swim endurance and swim behavior assays as functional readouts of spinal cord regeneration.

Due to their renowned regenerative capacity, adult zebrafish are a premier vertebrate model to interrogate mechanisms of innate spinal cord regeneration. ...

Neuroscience

A Real-World High-Intensity Interval Training Protocol for Cardiorespiratory Fitness Improvement

High-Intensity Interval Training (HIIT) has emerged as an interesting time-efficient approach to increase exercise adherence and improve health. However, few studies have tested the efficiency of HIIT protocols in a &#34;real world&#34; setting, e.g., HIIT protocols designed for outdoor spaces without specialized equipment. This study presents a &#34;real world&#34; training protocol, named &#34;beep training&#34;, and compares the efficiency of a HIIT regiment versus a traditional long-duration Moderate-Intensity Continuous Training (MICT) regiment using this beep training protocol on VO2 max of overweight untrained men. Twenty-two subjects performed outdoor running with MICT (n = 11) or HIIT (n = 11). Cardiorespiratory fitness was assessed before and after training protocols using a metabolic analyzer. Both training protocols were performed 3 days a week for 8 weeks using the Beep Test results. The MICT group performed the exercise program at 60%-75% of the maximum speed of the 20 m shuttle test (Vmax) and with a progression of the distance of 3,500-5,000 m. The HIIT group performed the interval exercise with 7-10 bouts of 200 m at 85%-100% of the maximum speed of the 20 m shuttle test (Vmax), interspersed with 1 min of passive recovery. Although the HIIT group presented a significantly lower training volume than the MICT group (p &#60; 0.05) after 8 weeks of beep training, HIIT was superior to MICT in improving VO2 max (MICT: ~4.1%; HIIT: ~7.3%; p &#60; 0.05). The &#34;real world&#34; HIIT regiment based on beep training protocol is a time-efficient, low-cost, and easy-to-implement protocol for overweight untrained men.

This study presents a low-cost and easy-to-implement "real world" high-intensity interval training (HIIT) protocol for scientific research and discusses its efficiency for cardiorespiratory fitness.

High-Intensity Interval Training (HIIT) has emerged as an interesting time-efficient approach to increase exercise adherence and improve health. However, ...

Real-Time Electrocardiogram Monitoring During Treadmill Training in Mice

Regular physical exercise is a major contributor to cardiovascular health, influencing various metabolic as well as electrophysiological processes. However, in certain cardiac diseases such as inherited arrhythmia syndromes, e.g., arrhythmogenic cardiomyopathy (ACM) or myocarditis, physical exercise may have negative effects on the heart leading to a proarrhythmogenic substrate production. Currently, the underlying molecular mechanisms of exercise-related proarrhythmogenic remodeling are largely unknown, thus it remains unclear which frequency, duration, and intensity of exercise can be considered safe in the context of disease(s).
The proposed method allows to study proarrhythmic/antiarrhythmic effects of physical exercise by combining treadmill training with real-time monitoring of the ECG. Implantable telemetry devices are used to continuously record the ECG of freely moving mice over a period of up to 3 months both at rest and during treadmill training. Data acquisition software with its analysis modules is used to analyze basic ECG parameters such as heart rate, P wave duration, PR interval, QRS interval, or QT duration at rest, during and after training. Furthermore, heart rate variability (HRV) parameters and occurrence of arrhythmias are evaluated. In brief, this manuscript describes a step-by-step approach to experimentally explore exercise induced effects on cardiac electrophysiology, including potential proarrhythmogenic remodeling in mouse models.

Electrocardiogram (ECG) is the key variable to understanding cardiac electrophysiology. Physical exercise has beneficial effects but may also be harmful in the context of cardiovascular diseases. This manuscript provides a method of recording real-time ECG during exercise, which can serve to investigate its effects on cardiac electrophysiology in mice.

Regular physical exercise is a major contributor to cardiovascular health, influencing various metabolic as well as electrophysiological processes. ...

A Rapidly Incremented Tethered-Swimming Maximal Protocol for Cardiorespiratory Assessment of Swimmers

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