This work was supported by the Natural Science Foundation of Chongqing, China (cstc2019jcyj-msxmX0046), the project of Chongqing Education Commission of China (KJQN202001127), and the project of Banan District Science and Technology Commission, Chongqing, China (2020TJZ010). The authors would like to thank Prof. Yan Yang for providing the test site. We are also grateful to Dr. Jingshu Wang and Dr. Jinghua Ma for their guidance of using the vibration measurement instrumentation. Thanks are also due to the subjects for their wholehearted cooperation during the experiments.

All procedures were approved by the Ethics Committee of Chongqing University of Technology and each subject provided written informed consent prior to participation in this study.
1. Hand tractor preparation
<ol>
	<li>Ensure the hand tractor is subjected to proper test conditions with a full fuel tank, without looseness of bolts, and without other mechanical defects that would result in abnormal vibration. 
	NOTE: The specifications of the hand tractor used in this experiment are given in Table 1.</li>
	<li>Place the hand tractor in a test site with a dry, firm, and level ground surface. 
	NOTE: If this experiment was conducted in an indoor laboratory, the laboratory must be well-ventilated to prevent any injurious effects of the exhaust gas from the hand tractor.</li>
	<li>Remove the dust cover of the engine pulley to conveniently calibrate the engine speed with a speedometer during the experiment.</li>
	<li>Remove the elastomeric materials of the handles according to ISO 5349-2 standard5.</li>
</ol>
2. Subject preparation
<ol>
	<li>Ensure that all subjects are healthy with no physical ailment and are above the age of 18 years3. Inform each subject about the study objectives and test procedures. Obtain written informed consent from all subjects.
	<ol>
		<li>Exclude subjects with the following diseases: primary Raynaud&#39;s disease or secondary Raynaud&#39;s phenomenon, impairment of blood circulation to the hands, deformity of bones and joints, disorders of the peripheral nervous system or musculoskeletal system3.</li>
	</ol>
	</li>
	<li>Ask subjects to wear sleeveless or short-sleeved clothing, and to remove watches, bracelets, rings, etc.</li>
	<li>Warn each subject not to touch the gear shift lever of the hand tractor during operation. Warn each subject to stay away from the engine pulley when the hand tractor is running.</li>
	<li>Provide subjects with speed regulation training on the hand tractor. Inform each subject to shut down the engine at the end of the experiment by pressing down on the engine switch button. 
	NOTE: Generally, the engine speed regulation is controlled by the throttle switch located on the right handle, and subjects are trained to regulate the engine speed by turning the throttle switch to the left (speed decrease) or to the right (speed increase) with their right hands.</li>
	<li>Instruct each subject how to operate the hand tractor and how to regulate the engine speed from 1500 rpm to 3500 rpm.</li>
	<li>Measure each subject&#39;s body dimensions (standing height, mass, forearm length, upper arm length, hand length). 
	NOTE: Table 2 summarizes the physical characteristics of ten healthy subjects in this experiment.</li>
	<li>Wrap the accelerometer adapters tightly on the hand and arm of each subject at the locations indicated in Figure 2. 
	&#8203;NOTE: Each adapter was fabricated using a nylon strap and a piece of the galvanized iron sheet (0.3 mm) to provide a rigid and light attachment.</li>
</ol>
3. Measurement system setup
<ol>
	<li>Acceleration measurement system setup 
	NOTE: The present steps aim to collect the vibration acceleration signals from the handle of the hand tractor and six locations of operator&#39;s hand-arm system. The proposed approach employs a compact Data Acquisition (DAQ) system composed of seven accelerometers, three data acquisition cards, a DAQ chassis, a laptop computer, and some associated cables (Figure 3). Other types of DAQ systems with proper characteristics for the involved application can be similarly applied.
	<ol>
		<li>Before initiating a measurement, gather all the components of the measurement system (accelerometers, data acquisition system, thin-film pressure sensing system, tachometer, digital goniometer, and other relevant components).</li>
		<li>To set up the acceleration measurement system, connect the accelerometer with the data acquisition cards using the accelerometer cables. Using an Ethernet cable, connect the chassis with the computer. 
		NOTE: Two tri-axial accelerometers and five single-axis accelerometers fixed with magnetic mounting base were used in this experiment.</li>
		<li>Attach one tri-axial accelerometer on the left handle of the hand tractor and attach the other one on the accelerometer adapter of the subject&#39;s hand. Attach single-axis accelerometers, one by one, on the accelerometer adapters of the subject&#39;s arm and shoulder. 
		NOTE: The locations of the accelerometers are as shown in Figure 1. The location selection of the tri-axial accelerometer on the left handle of the hand tractor should be as close to the operator&#39;s left hand as possible.</li>
		<li>Adjust the orientation of the tri-axial accelerometers on the hand to be consistent with the basicentric coordinate system (Figure 4) for measurement of hand-arm vibration refer to ISO 5349-1 standard4. Using adhesive tape, secure the accelerometer cables on the skin surface of the subject&#39;s arm and the tractor&#39;s handlebar.</li>
	</ol>
	</li>
	<li>Grip force measurement setup 
	NOTE: A thin-film pressure sensing system15,16 was designed with two resistive pressure sensitive sensors, a single-chip controller, and an LED display, and was calibrated before measurement, as shown in Figure 5.
	<ol>
		<li>Attach two thin-film sensors symmetrically on opposite sides around the central axis of the handle using double-sided adhesive tape.</li>
		<li>Place the screen of the sensing system at a convenient height so that the subject could monitor and adjust the grip force to the specified level during the operation of the hand tractor.</li>
	</ol>
	</li>
	<li>Engine speed measurement setup 
	NOTE: Engine speed refers to the revolutions per minute (RPM) of the propeller of the employed hand tractor engine, which equals to the RPM of the engine pulley. A laser tachometer was used to calibrate and monitor the engine speed during operation.
	<ol>
		<li>Attach a piece of retroreflective tape (approximately 10 &#215; 10 mm) to the engine pulley surface for laser tachometer measurement.</li>
		<li>Place the tachometer at a proper height and perpendicular to the retroreflective tape.</li>
	</ol>
	</li>
	<li>Posture measurement
	<ol>
		<li>Instruct the subject to hold and raise the handle to a horizontal position. Measure the subject&#39;s hand and arm posture using a digital goniometer. 
		&#8203;NOTE: The five angles17 used to describe the hand and arm posture during the operation of the hand tractor are shown in Figure 6. The subjects&#39; posture angles measured in this experiment are presented in Table 2.</li>
		<li>Ask the subject to maintain the posture until the end of the trial.</li>
	</ol>
	</li>
</ol>
4. Experiment and data acquisition
<ol>
	<li>Start the hand tractor in neutral and keep it running at a low engine speed (around 1500 rpm) for about 30 s until it stabilized.</li>
	<li>Turn on the tachometer, the thin-film pressure sensing device, the laptop computer and the acceleration data acquisition system, respectively.</li>
	<li>Open the DAQ software and create a new file for each subject. Set the parameters of acceleration, acquisition mode, and sampling rate for data collection. 
	NOTE: To obtain the accurate characterization of the HTV, the sampling rate should be no less than 1500 Hz. In this study, the sampling rate was set at 1650 Hz. If a more higher sampling rate was used for data collection, a low-pass filter with a cut-off frequency at 1500 Hz was advised to remove the noise influences such as the irrelevant high-frequency contributions.</li>
	<li>Click the Run and wait about 10 s until the system is stabilized. Then click Record to start recording the acceleration data.</li>
	<li>Adjustment of the engine speed and grip force 
	NOTE: As shown in Figure 7, this experiment was conducted at three levels of engine speed (1500, 2500 and 3500 rpm) and three levels of grip force (20, 30, and 40 N) during each trial. The approximate duration of each subject&#39;s HTV testing is 6 min.
	<ol>
		<li>Ask the subject to monitor the tachometer and adjust the engine speed to 1500 rpm until it stabilized.</li>
		<li>Instruct the subject adjust the grip force carefully to 20 N by looking at the displayed force signals from the thin-film pressure sensing system, and keep this grip force level for about 30 s. 
		NOTE: The adjustment of the grip force denotes the increase or decrease of pressure between the hand and the handlebar of the hand tractor. Subjects should perform the adjustment of the grip force through holding the handlebar more tightly or lightly.</li>
		<li>Adjust the grip force to 30 N and keep about 30 s. Then, adjust the grip force to 40 N and keep about 30 s.</li>
		<li>Adjust the engine speed to 2500 rpm and repeat steps 4.5.2 and 4.5.3.</li>
		<li>Adjust the engine speed to 3500 rpm and repeat steps 4.5.2 and 4.5.3.</li>
	</ol>
	</li>
	<li>Ask the subject to turn the throttle switch to the lowest engine speed. Put down the handle and shut down the engine of the hand tractor.</li>
	<li>Save the data and shut down the DAQ system. Remove and place the accelerometers on the next subject.</li>
	<li>Repeat steps 4.3 to 4.7 until the end of the data collections of all subjects.</li>
	<li>Export the acceleration time-series data for further analysis.</li>
</ol>
5. Data processing and analysis
<ol>
	<li>Import the recorded vibration time domain signals to MATLAB software. Calculate the root-mean-square (RMS) values of the vibration acceleration of hand tractor&#39;s handle, which represent the vibration exposure during the operation of the hand tractor, with the Equation (1): 
	<img alt="Equation 1" src="/files/ftp_upload/62508/62508eq01.jpg" /> (1) 
	where, aRMS&#160;is the RMS of vibration acceleration (m/s2) calculated for each 1/3rd octave band, a(t) is the measured vibration acceleration amplitude (m/s2), and T&#160;is the duration of the measured vibration acceleration (s). 
	NOTE: In ISO 5349-1 standard, it is important to use RMS acceleration to represent the magnitude of vibrations transmitted to the operator&#39;s hands.</li>
	<li>Calculate the RMS values of vibration acceleration on hand, wrist, arm and shoulder of each subject using Equation (1). Calculate the vibration transmissibility (TR) using Equation (2)1,14: 
	<img alt="Equation 2" src="/files/ftp_upload/62508/62508eq02.jpg" /> (2) 
	where, ain is the handle vibration for HTV, and aout is the respective vibration in the six locations of the subject&#39;s hand-arm system (see Figure 2). 
	NOTE: According to ISO 5349-1, the factors (except for grip force and vibration frequency) may influence the results of hand transmitted vibration measurement include: the operator&#39;s skill, body posture, climatic conditions, noise, etc. To decrease these random factors, the TR values of all the measurement locations of the ten subjects in this study were averaged.</li>
	<li>Convert the time domain signals of the handle to frequency domain signals by fast Fourier transform (FFT) algorithm using MATLAB program to examine the input vibration.</li>
</ol>

<ol>
	<li>Ahmadian, H., Hassan-Beygi, S. R., Ghobadian, B., Najafi, G. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=ANFIS+modeling+of+vibration+transmissibility+of+a+power+tiller+to+operator.">ANFIS modeling of vibration transmissibility of a power tiller to operator.</a> Applied Acoustics. 138, 39-51 (2018).</li><li>Heaver, C., Goonetilleke, K. S., Ferguson, H., Shiralkar, S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Hand-arm+vibration+syndrome:+a+common+occupational+hazard+in+industrialized+countries.">Hand-arm vibration syndrome: a common occupational hazard in industrialized countries.</a> Journal of Hand Surgery. 36 (5), 354-363 (2011).</li><li>Geethanjali, G., Sujatha, C. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Study+of+Biomechanical+Response+of+Human+Hand-Arm+to+Random+Vibrations+of+Steering+Wheel+of+Tractor.">Study of Biomechanical Response of Human Hand-Arm to Random Vibrations of Steering Wheel of Tractor.</a> Molecular &amp; Cellular Biomechanics. 10 (4), 303-317 (2013).</li><li>International Organization for Standardization. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=ISO+5349-1:+Mechanical+Vibration:+Measurement+and+Evaluation+of+Human+Exposure+to+Hand+Transmitted+Vibration+Part+1:+General+requirements.">ISO 5349-1: Mechanical Vibration: Measurement and Evaluation of Human Exposure to Hand Transmitted Vibration Part 1: General requirements.</a> International Organization for Standardization. , (2001).</li><li>International Organization for Standardization. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=ISO5349-2:+Mechanical+vibration-+Measurement+and+evaluation+of+human+exposure+to+hand-transmitted+vibration.+Part+2:+Practical+guidance+for+measurement+at+the+workplace.">ISO5349-2: Mechanical vibration- Measurement and evaluation of human exposure to hand-transmitted vibration. Part 2: Practical guidance for measurement at the workplace.</a> International Organization for Standardization. , (2001).</li><li>Besa, A. J., Valero, F. J., Su&#241;er, J. L., Carballeira, J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Characterisation+of+the+mechanical+impedance+of+the+human+hand-arm+system:+The+influence+of+vibration+direction,+hand-arm+posture+and+muscle+tension.">Characterisation of the mechanical impedance of the human hand-arm system: The influence of vibration direction, hand-arm posture and muscle tension.</a> International Journal of Industrial Ergonomics. 37 (3), 225-231 (2007).</li><li>Marcotte, P., Aldien, Y., Boileau, P. &. #. 2. 0. 1. ;., Rakheja, S., Boutin, J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Effect+of+handle+size+and+hand-handle+contact+force+on+the+biodynamic+response+of+the+hand-arm+system+under+zh-axis+vibration.">Effect of handle size and hand-handle contact force on the biodynamic response of the hand-arm system under zh-axis vibration.</a> Journal of Sound and Vibration. 283 (3-5), 1071-1091 (2005).</li><li>Pan, 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=The+relationships+between+hand+coupling+force+and+vibration+biodynamic+responses+of+the+hand-arm+system.">The relationships between hand coupling force and vibration biodynamic responses of the hand-arm system.</a> Ergonomics. 61 (6), 818-830 (2018).</li><li>Dong, R. G., Rakheja, S., Schopper, A. W., Han, B., Smutz, W. P. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Hand-transmitted+vibration+and+biodynamic+response+of+the+human+hand-arm:+a+critical+review.">Hand-transmitted vibration and biodynamic response of the human hand-arm: a critical review.</a> Critical Reviews In Biomedical Engineering. 29 (4), 393-439 (2001).</li><li>Marchetti, E., 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+investigation+on+the+vibration+transmissibility+of+the+human+elbow+subjected+to+hand-transmitted+vibration.">An investigation on the vibration transmissibility of the human elbow subjected to hand-transmitted vibration.</a> International Journal of Industrial Ergonomics. 62, 82-89 (2017).</li><li>McDowell, T. W., Welcome, D. E., Warren, C., Xu, X. S., Dong, R. G. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Assessment+of+hand-transmitted+vibration+exposure+from+motorized+forks+used+for+beach-cleaning+operations.">Assessment of hand-transmitted vibration exposure from motorized forks used for beach-cleaning operations.</a> Annals of Work Exposures and Health. 57 (1), 43-53 (2013).</li><li>Tony, B. J. A. R., Alphin, M. S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Finite+element+analysis+to+assess+the+biomechanical+behavior+of+a+finger+model+gripping+handles+with+different+diameters.">Finite element analysis to assess the biomechanical behavior of a finger model gripping handles with different diameters.</a> Biomedical Human Kinetics. 11 (1), 69-79 (2019).</li><li>Tony, B. J. A. R., Alphin, M. S., Velmurugan, D. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Influence+of+handle+shape+and+size+to+reduce+the+hand-arm+vibration+discomfort.">Influence of handle shape and size to reduce the hand-arm vibration discomfort.</a> Work. 63 (3), 415-426 (2019).</li><li>Dewangan, V. K. T. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Characteristics+of+hand-transmitted+vibration+of+a+hand+tractor+used+in+three+operational+modes.">Characteristics of hand-transmitted vibration of a hand tractor used in three operational modes.</a> International Journal of Industrial Ergonomics. 39 (1), 239-245 (2009).</li><li>Kalra, M., Rakheja, S., Marcotte, P., Dewangan, K. N., Adewusi, S. <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+coupling+forces+at+the+power+tool+handle-hand+interface.">Measurement of coupling forces at the power tool handle-hand interface.</a> International Journal of Industrial Ergonomics. 50, 105-120 (2015).</li><li>Gurram, R., Rakheja, S., Gouw, G. 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+study+of+hand+grip+pressure+distribution+and+EMG+of+finger+flexor+muscles+under+dynamic+loads.">A study of hand grip pressure distribution and EMG of finger flexor muscles under dynamic loads.</a> Ergonomics. 38 (4), 684-699 (1995).</li><li>Tarabini, M., Saggin, B., Scaccabarozzi, D., Moschioni, G. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Hand-arm+mechanical+impedance+in+presence+of+unknown+vibration+direction.">Hand-arm mechanical impedance in presence of unknown vibration direction.</a> International Journal of Industrial Ergonomics. 43 (1), 52-61 (2013).</li><li>Aatola, S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Transmission+of+vibration+to+the+wrist+and+comparison+of+frequency+response+function+estimators.">Transmission of vibration to the wrist and comparison of frequency response function estimators.</a> Journal of Sound and Vibration. 131 (3), 497-507 (1989).</li><li>Kihlberg, S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Biodynamic+response+of+the+hand-arm+system+to+vibration+from+an+impact+hammer+and+a+grinder.">Biodynamic response of the hand-arm system to vibration from an impact hammer and a grinder.</a> International Journal of Industrial Ergonomics. 16 (1), 1-8 (1995).</li><li>Gurram, R., Rakheja, S., Gouw, G. J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Vibration+transmission+characteristics+of+the+human+hand-arm+and+gloves.">Vibration transmission characteristics of the human hand-arm and gloves.</a> International Journal of Industrial Ergonomics. 13 (3), 217-234 (1994).</li><li>Burstr&#246;m, A. S. L. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Transmission+of+vibration+energy+to+different+parts+of+the+human+hand-arm+system.">Transmission of vibration energy to different parts of the human hand-arm system.</a> Int Arch Occup Environ Health. 70 (3), 199-204 (1997).</li><li>Hartung, E., Dupuis, H., Scheffer, M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Effects+of+grip+and+push+forces+on+the+acute+response+of+the+hand-arm+system+under+vibrating+conditions.">Effects of grip and push forces on the acute response of the hand-arm system under vibrating conditions.</a> International Archives of Occupational and Environmental Health. 64 (6), 463-467 (1993).</li><li>Pope, M. H., Magnusson, M., Hansson, T. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+upper+extremity+attenuates+intermediate+frequency+vibrations.">The upper extremity attenuates intermediate frequency vibrations.</a> Journal of Biomechanics. 30 (2), 103-108 (1997).</li><li>International Organization for Standardization. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=ISO+8041-1:+Human+response+to+vibration-Measuring+instrumentation.">ISO 8041-1: Human response to vibration-Measuring instrumentation.</a> International Organization for Standardization. , (2017).</li><li>Ying, Y. B., Zhang, L. B., Xu, F., Dong, M. D. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Vibratory+characteristics+and+hand-transmitted+vibration+reduction+of+walking+tractor.">Vibratory characteristics and hand-transmitted vibration reduction of walking tractor.</a> Transactions Of The ASAE. 41 (4), 917-922 (1998).</li><li>Dewangan, K. N., Tewari, V. K. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Characteristics+of+vibration+transmission+in+the+hand-arm+system+and+subjective+response+during+field+operation+of+a+hand+tractor.">Characteristics of vibration transmission in the hand-arm system and subjective response during field operation of a hand tractor.</a> Biosystems Engineering. 100 (4), 535-546 (2008).</li><li>Xu, X. S., 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=Vibrations+transmitted+from+human+hands+to+upper+arm,+shoulder,+back,+neck,+and+head.">Vibrations transmitted from human hands to upper arm, shoulder, back, neck, and head.</a> International Journal of Industrial Ergonomics. 62, 1-12 (2017).</li></ol>

The authors have nothing to disclose.

The protocol presented in this study was established based on HTV standards4,5,24, and was developed as the standard steps for the measurement of the HTV of the human hand-arm system during the operation of a hand tractor in a stationary condition. This condition is the most stable state of the hand tractor to help ensure the reliable measurement of the vibration actually transmitted to the hand and arm. The range of variables c...

Hand tractors, also known as power tillers, are widely used in developing countries for the land preparation of small fields. The field operation of a hand tractor involves walking behind the machine and holding its handles to control its movement. The operators of hand tractors are exposed to high levels of vibration, which could be attributed to the small single cylinder engine and lack of suspension system of hand tractors1. The hand-arm vibration syndrome (HAVS)2 can be caused by long-period endurance from the vibration, named hand transmitted vibration (HTV), which generated by the hand tractor and received by the operator&#39;s hands. To assess the health risks derived by operators&#39; exposure to the HTV of hand tractors, it is necessary to establish a method for the measurement of the vibration response of the hand-arm system.
The hand-arm system is composed of bones, muscles, tissues, veins and arteries, tendons and skin3, and the direct measurement of HTV poses many problems. The relevant international standards4,5 provide guidelines pertaining to the measurement of the severity of vibration generated in the immediate vicinity of the hand, including the coordinate system for the hand, the location and mounting of accelerometers, the measurement duration, cable connector problems, etc. However, the standards do not take into consideration intrinsic variables, such as the grip force, the posture of the hand and arm, individual factors, etc. These factors have been examined extensively under a wide range of vibration excitations and test conditions6,7,8,9,10,11,12,13, but the results of different investigators are not in good agreement. Many of these factors have not been sufficiently understood to be incorporated into standard methods. This restriction is partially attributable to the complexities of the human hand-arm system, the test conditions, and the differences in the experimental and measurement techniques employed.
Moreover, most of the earlier measurements of HTV were performed under carefully controlled conditions with idealized vibration excitations, grip force, and postural conditions. The findings and experimental procedures of these measurements, therefore, may not truly replicate real-world conditions, such as the operating conditions of hand tractors. Moreover, only limited efforts have been undertaken to study the HTV of hand tractors with field measurements. These measurements were performed using accelerometers attached to the operator&#39;s wrist, arm, chest, and head to measure the whole body vibration under the tractor&#39;s transportation conditions1, or under the conditions of tilling in an untilled field and puddling in a submerged field with different levels of engine speeds14. The effect of the grip force, which could be a crucial factor of HTV7,8, was not isolated. These methods are therefore unsuitable as standardized measurement procedures due to the operator&#39;s various forced postures during farming ascribed to the harsh environmental conditions.
The present research was undertaken to contribute to the establishment of reliable and repeatable procedures for the HTV measurement of hand tractors in a stationary mode. Figure 1 presents the schematic diagram of the experimental design. A hand tractor manufactured in China and commonly used by Chinese farmers was employed, and ten research workers were chosen as subjects for the study. Seven lightweight piezoelectric accelerometers attached to the tractor-hand-arm system were used to measure the vibration. One tachometer and two thin-film pressure sensors monitored the engine speed and grip force during testing. The subjects were required to sequentially operate the hand tractor at specified engine speeds and with specified grip forces to obtain the vibration characteristics in various operational modes. This manuscript provides a detailed protocol for the HTV measurement of the tractor-hand-arm system with unique consideration of changes in the grip force and vibration frequency.

<table><tbody><tr><td>Accelerometers</td><td>PCB Piezotronics Inc.</td><td>352C33, 356A04</td><td>Used to measure vibration signals. Including 2 tri-axial accelerometers and 5 single-axis accelerometers.</td></tr><tr><td>CompactDAQ System</td><td>National Instruments</td><td>cRIO-9045,NI-9234 C</td><td>Used for acceleration acquisition. The system consists of a chassis and 3 data acquisition cards.</td></tr><tr><td>Digital caliper</td><td>Sanliang</td><td>160800635</td><td>Used to measure dimensions of the hand.</td></tr><tr><td>Digital goniometer</td><td>Sanliang</td><td>802973</td><td>Used to measure hand and arm posture.</td></tr><tr><td>Laptop computer</td><td>Lenovo</td><td>Ideapad 500s</td><td>To run the softwares.</td></tr><tr><td>Matlab</td><td>MathWorks Inc.</td><td>Version 2020a</td><td>Used for data processing.</td></tr><tr><td>NI SignalExpress</td><td>National Instruments</td><td>Trial version 2015</td><td>Use to acquire, analyze and present acceleration data.</td></tr><tr><td>Tachometer</td><td>Sanliang</td><td>TM 680</td><td>Used to measure engine speed.</td></tr><tr><td>Thin-film pressure sensing system</td><td>YourCee</td><td>n/a</td><td>Used to measure grip force. The system consists of 2 thin-film sensors, a STM32 singlechip and a LED display.</td></tr></tbody></table>

measurement of the hand transmitted vibration of the human hand arm system during operation of a hand tractor

Operators of hand tractors are exposed to high levels of hand transmitted vibration (HTV). This vibration, which can be both irksome and hazardous to human health, is imparted to the operator via his or her hands and arms. However, a standardized method for measuring HTV of hand tractors has yet to be defined. The aim of the study was to present an experimental method for the investigation of the biodynamic response and vibration transmissibility of the hand-arm system during the operation of a hand tractor in a stationary mode. Measurements were performed with ten subjects using three grip forces and three handle vibration levels to examine the influences of the hand pressure and frequency on hand transmitted vibration (HTV). The results indicate that the tightness of grip on the handle influences the vibration response of the hand-arm system, especially at frequencies between 20 and 100 Hz. The transmission of lower frequencies in the hand-arm system was relatively unattenuated. In comparison, attenuation was found to be quite marked for higher frequencies during the operation of the hand tractor. The vibration transmissibility to different parts of the hand-arm system decreased with the increase of the distance from the vibration source. The proposed methodology contributes to the collection of consistent data for the evaluation of operator vibration exposure and the ergonomics development of hand tractors.

The experiment was carried out in the laboratory (air temperature 22.0 &#176;C &#177; 1.5 &#176;C) on ten healthy subjects (Table 2) during the operation of a hand tractor in a stationary condition.
Following the protocol, vibration acceleration data were collected from the handle of the hand tractor, as well as the back of the hand, the wrist, the arm, and the shoulder of each subject. The spectrum of the vibration acceleration occurring at the handle (input to the hand) was ...

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Measurement of the Hand Transmitted Vibration of the Human Hand Arm System During Operation of a Hand Tractor

Here, we present a standardized method for measurement of the hand transmitted vibration from handles of a single-axle tractor with special reference to changes in grip force and vibration frequency.

Operators of hand tractors are exposed to high levels of hand transmitted vibration (HTV). This vibration, which can be both irksome and hazardous to ...

measurement-hand-transmitted-vibration-human-hand-arm-system-during

Research

JoVE Journal

Engineering

4.3K Views.  Chongqing University of Technology. Here, we present a standardized method for measurement of the hand transmitted vibration from handles of a single-axle tractor with special reference to changes in grip force and vibration frequency.

Video: Measurement of the Hand Transmitted Vibration of the Human Hand Arm System During Operation of a Hand Tractor

Measurement of Vibration Detection Threshold and Tactile Spatial Acuity in Human Subjects

Tests that allow the precise determination of psychophysical thresholds for vibration and grating orientation provide valuable information about mechanosensory function that are relevant for clinical diagnosis as well as for basic research. Here, we describe two psychophysical tests designed to determine the vibration detection threshold (automated system) and tactile spatial acuity (handheld device). Both procedures implement a two-interval forced-choice and a transformed-rule up and down experimental paradigm. These tests have been used to obtain mechanosensory profiles for individuals from distinct human cohorts such as twins or people with sensorineural deafness.

Here, we present protocols to determine vibration detection thresholds and tactile acuity using psychophysical methods in man.

Tests that allow the precise determination of psychophysical thresholds for vibration and grating orientation provide valuable information about ...

Behavior

Method to Measure Tone of Axial and Proximal Muscle

The control of tonic muscular activity remains poorly understood. While abnormal tone is commonly assessed clinically by measuring the passive resistance of relaxed limbs1, no systems are available to study tonic muscle control in a natural, active state of antigravity support. We have developed a device (Twister) to study tonic regulation of axial and proximal muscles during active postural maintenance (i.e. postural tone). Twister rotates axial body regions relative to each other about the vertical axis during stance, so as to twist the neck, trunk or hip regions. This twisting imposes length changes on axial muscles without changing the body's relationship to gravity. Because Twister does not provide postural support, tone must be regulated to counteract gravitational torques. We quantify this tonic regulation by the restive torque to twisting, which reflects the state of all muscles undergoing length changes, as well as by electromyography of relevant muscles. Because tone is characterized by long-lasting low-level muscle activity, tonic control is studied with slow movements that produce "tonic" changes in muscle length, without evoking fast "phasic" responses. Twister can be reconfigured to study various aspects of muscle tone, such as co-contraction, tonic modulation to postural changes, tonic interactions across body segments, as well as perceptual thresholds to slow axial rotation. Twister can also be used to provide a quantitative measurement of the effects of disease on axial and proximal postural tone and assess the efficacy of intervention.

We have developed a device (Twister) to study the regulation of tonic muscle activity during active postural maintenance. Twister measures torsional resistance and muscular responses in standing subjects during twisting of the body axis. The device can be flexibly configured to study various aspects of tonic control across the neck, trunk, and/or hips.

The control of tonic muscular activity remains poorly understood.  While abnormal tone is commonly assessed clinically by measuring the passive resistance ...

Medicine

Simulation of Human-induced Vibrations Based on the Characterized In-field Pedestrian Behavior

For slender and lightweight structures, vibration serviceability is a matter of growing concern, often constituting the critical design requirement. With designs governed by the dynamic performance under human-induced loads, a strong demand exists for the verification and refinement of currently available load models. The present contribution uses a 3D inertial motion tracking technique for the characterization of the in-field pedestrian behavior. The technique is first tested in laboratory experiments with simultaneous registration of the corresponding ground reaction forces. The experiments include walking persons as well as rhythmical human activities such as jumping and bobbing. It is shown that the registered motion allows for the identification of the time variant pacing rate of the activity. Together with the weight of the person and the application of generalized force models available in literature, the identified time-variant pacing rate allows to characterize the human-induced loads. In addition, time synchronization among the wireless motion trackers allows identifying the synchronization rate among the participants. Subsequently, the technique is used on a real footbridge where both the motion of the persons and the induced structural vibrations are registered. It is shown how the characterized in-field pedestrian behavior can be applied to simulate the induced structural response. It is demonstrated that the in situ identified pacing rate and synchronization rate constitute an essential input for the simulation and verification of the human-induced loads. The main potential applications of the proposed methodology are the estimation of human-structure interaction phenomena and the development of suitable models for the correlation among pedestrians in real traffic conditions.

A protocol is presented for the characterization of the in-field pedestrian behavior and the simulation of the resulting structural response. Field-tests demonstrate that the in situ identified pacing rate and synchronization rate among the participants constitute an essential input for the simulation and verification of the human-induced loads.

For slender and lightweight structures, vibration serviceability is a matter of growing concern, often constituting the critical design requirement. With ...

An Objective and Child-friendly Assessment of Arm Function by Using a 3-D Sensor

Progressive and irreversible muscle atrophy characterizes Spinal Muscular Atrophy (SMA) and other similar muscle disorder diseases. Objective assessment of muscle functions is an essential and important, although challenging, prerequisite for successful clinical trials. Current clinical rating scales restrain the movement abnormalities to certain predefined coarse-grained individual items. The Kinect 3-D sensor has emerged as a low-cost and portable motion sensing technology used to capture and track people&#39;s movement in many medical and research fields. A novel approach using this 3-D sensor was developed and a game-like test was designed to objectively measure the upper limb function of patients with SMA. The prototype test targeted joint movement capability. While sitting in a virtual scene, the patient was instructed to extend, flex, and lift the whole arm in order to reach and place some objects. Both kinematic and spatiotemporal characteristics of upper limb movement were extracted and analyzed, e.g., elbow extension and flexion angles, hand velocity, and acceleration. The first study included a small cohort of 18 ambulant SMA patients and 19 age- and gender-matched healthy controls. A comprehensive analysis of arm movement was achieved; however, no significant difference between the groups were found due to the mismatch of patient&#39;s capability and the test difficulty. Based on this experience, a second version of the test consisting of a modified version of the first game with increased difficulties and a second game targeting muscle endurance were designed and implemented. The new test has not been conducted in any patient groups yet. Our work has demonstrated the potential capability of the 3-D sensor in assessing such muscle function and suggested an objective approach to complement the clinical rating scales.

An objective measure of muscle functions is challenging especially in children. Based on a commercially available digital 3-D sensor, a child-friendly gaming test was developed to assess upper limb function for clinical trials.

Progressive and irreversible muscle atrophy characterizes Spinal Muscular Atrophy (SMA) and other similar muscle disorder diseases. Objective assessment ...

A Simple Non-invasive Method for Temporary Knockdown of Upper Limb Proprioception

Proprioception may be the least well measured of all contributors to the neural control of movement. New precise, reliable measures of proprioception are needed for clinical diagnosis of impairment, and to measure outcomes of proprioceptive training. The purpose of this simple, non-invasive method is to temporarily knockdown upper limb proprioception in healthy adults, to an extent that would be useful in the development and testing of upper limb proprioception measures. Knockdown models have two main advantages over studying humans with impaired proprioception: participant availability and the ability to control the extent of impairment across participants. Current published methods of temporary proprioception knockdown of the upper limb, such as ischemic nerve blocks and cryotherapy, are invasive, impractical, or uncomfortable for the participant. Here, vibration over the ulnar groove was used to reduce upper limb proprioception. High frequency vibration may reduce proprioceptive acuity by inhibiting pacinian corpuscle-induced input. The effect of vibration used in this protocol was confirmed using two quantitative measures. This method was simple to administer, comfortable for participants, and practical.

The goal of this protocol is to demonstrate a practical method to temporarily interfere with proprioception in the upper limb of healthy humans.

Proprioception may be the least well measured of all contributors to the neural control of movement. New precise, reliable measures of proprioception are ...

Measuring the Motor Aspect of Cancer-Related Fatigue using a Handheld Dynamometer

Cancer-related fatigue (CRF) is commonly reported by patients both during and after receiving treatment for cancer. Current CRF diagnoses rely on self-report questionnaires which are subject to report and recall biases. Objective measurements using a handheld dynamometer, or handgrip device, have been shown in recent studies to correlate significantly with subjective self-reported fatigue scores. However, variations of both the handgrip fatigue test and fatigue index calculations exist in the literature. The lack of standardized methods limits the utilization of the handgrip fatigue test in the clinical and research settings. In this study, we provide detailed methods for administering the physical fatigue test and calculating the fatigue index. These methods should supplement existing self-reported fatigue questionnaires and help clinicians assess fatigue symptom severity in an objective and quantitative manner.

Simple and accessible methods were developed to measure the motor aspect of cancer-related fatigue objectively and quantitatively. We describe, in detail, ways to administer the physical fatigue test using a simple handgrip device as well as methods to calculate fatigue indices.

Cancer-related fatigue (CRF) is commonly reported by patients both during and after receiving treatment for cancer. Current CRF diagnoses rely on ...

Cancer Research

Whole Body Vibration Methods with Survivors of Polio

The purpose of the original study was to examine the use of whole body vibration (WBV) on polio survivors with and without post-polio syndrome as a form of weight bearing exercise. The goal of this article is to highlight the strengths, limitations, and applications of the method used. Fifteen participants completed two intervention blocks with a wash-out period in between the blocks. Each block consisted of twice a week (four weeks) WBV interventions, progressing from 10 to 20 min per session. Low intensity (peak to peak displacement 4.53 mm, frequency 24 Hz, g force 2.21) and higher intensity (peak to peak displacement 8.82 mm, frequency 35 Hz, g force 2.76) WBV blocks were used. Pain severity significantly improved in both groups following higher intensity vibration. Walking speed significantly improved in the group who participated in higher intensity intervention first. No study-related adverse events occurred. Even though this population can be at risk of developing overuse-related muscle weakness, fatigue, or pain from excessive physical activity or exercise, the vibration intensity levels utilized did not cause significant muscle weakness, pain, fatigue, or sleep disturbances. Therefore, WBV appears to provide a safe method of weight bearing exercise for this population. Limitations included the lack of measurement of reflexes, muscular activity, or circulation, the difficulty in participant recruitment, and insufficient strength of some participants to stand in recommended position. Strengths included a standard, safe protocol with intentional monitoring of symptoms and the heterogeneity of the participants in their physical abilities. An application of the methods is the home use of WBV to reduce the barriers associated with going to a facility for weight bearing exercise for longer term interventions, and benefits for conditions such as osteoporosis, particularly for aging adults with mobility difficulties due to paralysis or weakness. Presented method may serve as a starting point in future studies.

The goal of this article is to highlight the strengths, limitations, and applications of the method used with whole body vibration on polio survivors with and without post-polio syndrome as a feasible and safe form of weight bearing exercise.

The purpose of the original study was to examine the use of whole body vibration (WBV) on polio survivors with and without post-polio syndrome as a form ...

Applying Incongruent Visual-Tactile Stimuli during Object Transfer with Vibro-Tactile Feedback

The application of incongruent sensory signals that involves disrupted tactile feedback is rarely explored, specifically with the presence of vibrotactile feedback (VTF). This protocol aims to test the effect of VTF on the response to incongruent visual-tactile stimuli. The tactile feedback is acquired by grasping a block and moving it across a partition. The visual feedback is a real-time virtual presentation of the moving block, acquired using a motion capture system. The congruent feedback is the reliable presentation of the movement of the block, so that the subject feels that the block is grasped and see it move along with the path of the hand. The incongruent feedback appears as the movement of the block diverts from the actual movement path, so that it seems to drop from the hand when it is actually still held by the subject, thereby contradicting the tactile feedback. Twenty subjects (age 30.2 &#177; 16.3) repeated 16 block transfers, while their hand was hidden. These were repeated with VTF and without VTF (total of 32 block transfers). Incongruent stimuli were presented randomly twice within the 16 repetitions in each condition (with and without VTF). Each subject was asked to rate the difficulty level of performing the task with and without the VTF. There were no statistically significant differences in the length of the hand paths and durations between transfers recorded with congruent and incongruent visual-tactile signals &#8211; with and without the VTF. The perceived difficulty level of performing the task with the VTF significantly correlated with the normalized path length of the block with VTF (r = 0.675, p = 0.002). This setup is used to quantify the additive or reductive value of VTF during motor function that involves incongruent visual-tactile stimuli. Possible applications are prosthetics design, smart sport-wear, or any other garments that incorporate VTF.

We present a protocol to apply incongruent visual-tactile stimuli during an object transfer task. Specifically, during block transfers, performed while the hand is hidden, a virtual presentation of the block shows random occurrences of false block drops. The protocol also describes adding vibrotactile feedback while performing the motor task.

The application of incongruent sensory signals that involves disrupted tactile feedback is rarely explored, specifically with the presence of vibrotactile ...

Tactile Vibrating Toolkit and Driving Simulation Platform for Driving-Related Research

Collision warning system plays a key role in the prevention of driving distractions and drowsy driving. Previous studies have proven the advantages of tactile warnings in reducing driver&#8217;s brake response time. At the same time, tactile warnings have been proved effective in take-over request (TOR) for partially autonomous vehicles.
How the performance of tactile warnings can be optimized is an ongoing hot research topic in this field. Thus, the presented low-cost driving simulation software and methods are introduced to attract more researchers to take part in the investigation. The presented protocol has been divided into five sections: 1) participants, 2) driving simulation software configuration, 3) driving simulator preparation, 4) vibrating toolkit configuration and preparation, and 5) conducting the experiment.
In the exemplar study, participants wore the tactile vibrating toolkit and performed an established car-following task using the customized driving simulation software. The front vehicle braked intermittently, and vibrating warnings were delivered whenever the front vehicle was braking. Participants were instructed to respond as quickly as possible to the sudden brakes of the front vehicle. Driving dynamics, such as the brake response time and brake response rate, were recorded by the simulation software for data analysis.
The presented protocol offers insight into the exploration of the effectiveness of tactile warnings on different body locations. In addition to the car-following task that is demonstrated in the exemplar experiment, this protocol also provides options&#160;to apply other paradigms to the driving simulation studies by making simple software configuration without any code development. However, it is important to note that due to its affordable price, the driving simulation software and hardware introduced here may not be able to fully compete with other high-fidelity commercial driving simulators. Nevertheless, this protocol can act as an affordable and user-friendly alternative to the general high-fidelity commercial driving simulators.

This protocol describes a driving simulation platform and a tactile vibrating toolkit for the investigation of driving-related research. An exemplar experiment exploring the effectiveness of tactile warnings is also presented.&#160;

Collision warning system plays a key role in the prevention of driving distractions and drowsy driving. Previous studies have proven the advantages of ...

A Method for Evaluating Timeliness and Accuracy of Volitional Motor Responses to Vibrotactile Stimuli

Artificial sensory feedback (ASF) systems can be used to compensate for lost proprioception in individuals with lower-limb impairments. Effective design of these ASF systems requires an in-depth understanding of how the parameters of specific feedback mechanism affect user perception and reaction to stimuli. This article presents a method for applying vibrotactile stimuli to human participants and measuring their response. Rotating mass vibratory motors are placed at pre-defined locations on the participant's thigh, and controlled through custom hardware and software. The speed and accuracy of participants' volitional responses to vibrotactile stimuli are measured for researcher-specified combinations of motor placement and vibration frequency. While the protocol described here uses push-buttons to collect a simple binary response to the vibrotactile stimuli, the technique can be extended to other response mechanisms using inertial measurement units or pressure sensors to measure joint angle and weight bearing ratios, respectively. Similarly, the application of vibrotactile stimuli can be explored for body segments other than the thigh.

This article describes a technique for applying vibrotactile stimuli to the thigh of a human participant, and measuring the accuracy and reaction time of the participant&#39;s volitional response for various combinations of stimulation location and frequency.

Artificial sensory feedback (ASF) systems can be used to compensate for lost proprioception in individuals with lower-limb impairments.  Effective design ...