J Exerc Rehabil > Volume 14(2);2018 > Article
Hyun and Ryew: Kinetic analysis of downward step posture according to the foothold heights and visual information blockage in cargo truck


The study was undertaken to compare and analyze kinetic variables during downward foot-on according to the foothold heights under interrupted-visual information on 25-t cargo truck. Skilled adult male drivers (n=10) engaged in cargo truck driving over 1 year participated in the experiment. The results obtained from cinematographic and ground reaction force data during downward foot-on as follows; First, leg stiffness, peak vertical force (PVF) and loading rate showed significant difference as an increase of foothold heights, that is, interrupted-visual information showed greater impulse force than as was not. Second, variables of center of pressure (COP) with interrupted-visual information did not showed difference, but anterior-posterior COP and COP area showed an increasing tendency as an increase of foothold heights. Third, dynamic posture stability index (overall, medial-lateral, anterior-posterior, and vertical) showed significant difference as an increase of foothold height, that is, interrupted-visual information showed lower index than as was not. Therefore it will be possible to control successfully the leg stiffness, loading rate, and PVF when preparing an estimate for air phase time and impulse force through habitual cognition and confirmation at landing during downward foot-on from cargo truck. Identifying these potential differences may enable clinicians to assess type of injury and design exercise rehabilitation protocols specific.


Worldwide overland transport business requires several millions of an employee, most of whom consist of male truck driver (van der Beek, 2012). Tasks of cargo truck is to drive for distribution of various cargos, therefore the continuous observation of traffic situation and locomotion due to tight schedule of distribution etc. results in an increase of mental fatigue by overwork load (van der Beek, 2012).
In addition to fatigue of truck drivers, they were always exposed to lumbar back pain and disorder with excessive vibration against whole body (Bovenzi et al., 2006; Seidel, 1993), epidemiology of which showed more cases of disorder of back pain and handicap of vertebrae disk in exposed group to vibration than as was not (Bovenzi and Hulshof, 1999; Hulshof and van Zanten, 1987). Also Andrusaitis et al. (2006) reported that 249 of 489 (59%) truck driver experienced various the back pain of vertebrae.
That is, truck driver encountering the several dangerous factors due to long-time driving steps down ordinarily not only in a condition of increased pain of muscular skeletal part of waist, neck, shoulder ect. (Hedberg, 1985; Krause et al., 1997; Rossignol et al., 2003; van der Beek et al., 1993), but also of lowered level of sensibility and motor ability. Because of truck’s higher seat height made for cargo transportation in contrast to other vehicles, most drivers during up and downward stepping must be ready to suffer the falling accident both inconvenience and falling risk simultaneously (Hyun and Ryew, 2017). Ryew and Hyun (2013) of preceded study related with downward stepping on bus stair reported that 27.00±1.32 cm of 1st stair, 26.50±2.17 cm of 2nd stair, and 37.66±0.28 cm of 3rd stair height respectively, the 3rd stair height of which was too high and very inconvenient as of 3.70 N/BW of peak vertical force (PVF) in descending.
Particularly it was reported that wrong downward stepping may increase an injury risk at knee joint due to situation of interrupted-visual information during the nighttime by irregular driving schedule (Coggon et al., 2000; Maetzel et al., 1997; Sandmark et al., 2000). Visual information at landing provides preliminary confirming of spatial information against landing point and controls preparatory role of joint and muscle activity to absorb an impulse force at landing (Sidaway et al., 1989), but interrupted visual information of the height against landing point results in reduced stability according to increase of ground reaction force (GRF) in x–y axis, loading rate and PVF (Koh et al., 2011). Therefore injury risk on muscular-skeletal system may be increased when did not absorb an impulse force occurring at landing of foot (Nigg et al., 1987). In spite of subsidiary hand rail attached to exit door to resolve an inconvenience, most driver prefers to jump directly from seat (Fathallah and Cotnam, 2000). It is necessary quantitative materials for predicts and prevents the risk possibility of injury during landing from cargo truck.
That is, the aim of the study was to compare and analyze the kinetic variables during downward foot-on according to the foothold heights under interrupted-visual information on 25-t cargo truck.



Skilled adult male drivers (n=10; mean year, 29.3±6.18 years; mean heights, 177.78±2.30 cm; mean weights, 76.17±2.34 kg) engaged in cargo truck driving over 1 year participated in the experiment. Experimental design for this was reviewed and approved from Bioethics Committee of Jeju National University (JJNU-IRB-2016-024-001) and all of whom understood and consented on the purpose and details of the study.

Experimental procedure

After 25-t cargo truck owner’s consents, the truck made of 3 footholds for downward stepping was set up within indoor truck house with three-dimensional cinematography and GRF (AMTI-OR-7, Advanced Mechanical Technology Inc., Watertown, MA, USA) equipments under lateral side of driver seat. Height difference of between GRF plate and ground surface was adjusted on wheel and leveled with wooden box similar to height of GRF plate (Fig. 1). Then GRF (1 ea) data was collected at sample rate at 1,000 Hz, similar wooden box was installed widely to reduce data errors occurring by stepping anxiety due to narrowed landing area.
The 4 ea Camcorder camera (HDR/HDV 1980i, Sony Corp, Tokyo, Japan) and its light facility were installed within controlled spatial range which can capture an entire downward stepping motion, and set up at 60 frame/sec of camera speed and 1/500 sec of exposure time respectively. Body segment parameter (Plagenhoef et al., 1983) to calculate center of mass and velocity of whole body and total 19 digitizing points on body were applied to lower extremities model of the study (Fig. 2). The experiment was performed in order of the total 4 types of utilization of handrail on the 1st (1), 2nd (2), 3rd (3) stair according to whether secured or interrupted of visual information and jumping from driver’s seat directly (4) (1 subject: 2×4 trials) (Fig. 3).
Experimental procedure was measured the same trial repeatedly during the daytime in case of secured-visual information and the nighttime in case of interrupted-visual information respectively. Then at the nighttime, all subjects wore an eye-patch additionally for complete interrupted visual information from camera’s light facility. On the basis of that impulse force increased according to height’s increase between foot and ground surface during downward stepping of bus (Hyun and Ryew, 2014), The distance between truck and GRF plate was fixed on one’s preferred distance through preliminary practice.

Definition of analysis phase

Dimensionless model of leg stiffness was known as proper criterion on the motion evaluation in a situation of an increasing movement of leg’s length in human activities, which stiffness variables was made up the vertical GRF force (normalized body weight) and change rate (%) of leg length and was evaluated in a way of ignoring the unit of two variables (Sider et al., 2015).
is defined as normalized value divided PVF with body weight, also
Fmax is normalized value of change rate (%) of leg length, lo is shortest length of leg at ground landing as an estimate of leg length, then leg length delivered from COP to center of gravity (COG) of pelvic was cited from muscular-skeletal system model (Delp et al., 1990).

Analysis and process of data

The average and the standard deviation of the calculated variables were obtained using IBM SPSS Statistics ver. 21.0 (IBM Co., Armonk, NY, USA), performed repeated measures two-way analysis of variance according to interrupted visual information and foothold heights and performed the post hoc test (Duncan) at (P<0.05) in case of significant level respectively.


The results from kinetic variables and stiffness of lower leg according to interrupted-visual information (1st, 2nd, and 3rd stair) and foothold heights from cargo truck was as (Table 1). Kinetic variables and stiffness of lower leg according to interrupted-visual information (1st, 2nd, and 3rd stair) and foothold heights showed significant difference (P<0.001), followed in order of driver seat>3rd>2nd>1st stair. Also PVF and loading rate showed the same results, followed in order of driver seat>3rd>1st, 2nd stair at PVF, and driver seat>3rd>1st stair (P<0.05) respectively.
The results from COP according to interrupted-visual information (1st, 2nd, and 3rd stair) and foothold heights from cargo truck was as (Table 2). Medial lateral (ML)-COP, anterior posterior (AP)-COP, and COP area according to interrupted-visual information (1st, 2nd, and 3rd stair) did not showed significant difference (P>0.05), but and foothold heights showed significant level (P<0.05), and followed in order of driver seat>3rd>1st stair of ML-COP, driver seat>1st, 2nd, 3rd stair of AP-COP, and driver seat>3rd, 2nd>1st of COP area respectively.
The results from stiffness of leg and kinetic variables according to interrupted-visual information (1st, 2nd, and 3rd stair) and foothold heights from cargo truck was as (Table 3). Medial lateral stability index (MLSI), APSI, vertical (V)SI, and dynamic postural stability index (DPSI) showed significant difference (P>0.05), and followed in order of driver seat>3rd>1st stair of MLSI, APSI, VSI, and DPSI, but driver, 3rd>1st, 2nd (P<0.05) respectively.


There is nowadays many types of information and model on exercise prescription and rehabilitation diagnosis for vibration exposure and back pain of body resulted from long time driving. Clear diagnosis and prescription are very important to maximize the effectiveness of exercise rehabilitation depending on the type of injury in truck driver (Hyun and Ryew, 2017). But causes and effects and quantitative materials between impact types and injury occurrence is still not enough in spite of higher injury possibility and fatal wound during downward stepping from cargo truck.
Spring-mass model defined lower leg of body as linear spring without no mass, and it had close relationship with change rate of leg length during supporting phase and PVF (Farley et al., 1993). It was reported that stiffness of lower leg showed rather difference in line with ground conditions on which foot contacts, and it was in inverse proportion to stiffness of surface touched during exercise (Alexander, 1989; Feehery, 1986). Therefore some level of stiffness should be maintained for the fittest performance of human movement (Arampatzis et al., 1999; Dutto and Smith, 2002; Kerdok et al., 2002; Kuitunen et al., 2002; McMahon and Cheng, 1990; Seyfarth et al., 2002; Stefanyshyn and Nigg, 1998), but it may be failed to control of leg stiffness by rapid change of PVF and length of lower leg during jumping or downward stepping from vertical height of driver’s seat to solid surface.
That is, downward stepping from 1st stair of truck with noninterrupted visual information showed similar value with 35 (dimensionless) of stiffness value during running, proportional increasing trend of 2nd and 3rd, and showed about 2 times of 44 (dimensionless) of added body weight (30%) during running in case of downward stepping from driver seat (Silder et al., 2015). Also PVF and loading rate showed significant increase according to foothold height, and showed similar pattern with leg stiffness in the study.
Particularly leg stiffness, PVF, and loading rate showed larger increased pattern in interrupted-visual information than was not case. These result partly coincided with report of Santello et al. (2001) which could not be controlled and shown the more variability of impulse force in case of interrupted-visual information and be controlled the consistent performance of movement during landing. Loading rate is value of PVF divided by applied time, which means elapsed time to PVF point by body weight (Diss, 2001), and high loading rate means not only limited absorption of impulse at landing but also pressure of stress against lower leg for a short time (Hargrave et al., 2003). Also because leg stiffness is closely related with PVF and change rate of lower leg (%) (Donelan and Kram, 2000; Farley and González, 1996; McMahon and Cheng, 1990), increased lower leg’s stiffness means a degree of stiffness and rigidity of lower leg.
Therefore the more flexed type of knee joint during locomotion may reduce impulse force, vertical stiffness, impact absorption, impulse force transferred to skull (Hewett et al., 1999; McMahon et al., 1987; McNitt-Gray, 1993), but in case of downward stepping motion from high foothold height of cargo truck, an impact absorption mechanism may be neglected unconsciously. Particularly visual information may make preparation for activities of joint and muscle to absorb an impact occurring at landing by preliminary recognition on spatial distance against landing point (Santello et al., 2001; Sidaway et al., 1989), but interrupted-visual information may take a mechanism to limit the movement of ankle in the course of securing of stability (Kuo, 1995; Kuo and Zajac, 1993). In that the former mechanism can adopt manageable strategy prior to ground landing in various impact situations (Santello et al., 2001), interrupted-visual information on the foothold heights during downward foot-on from cargo truck enables to increase the leg stiffness, PVF, and loading rate for continuous supplementation of deficit feedback on visual information.
COP variables as stability index in the study was defined as the center of action of GRF vector occurring alongside with rectangular coordinates (two-dimensional [ML, AP]) against horizontal plane and was evaluated in unit of time-serial function (Kapteyn et al., 1983). That is, it did not showed difference in case of interrupted visual information, but showed increasing trend according to truck’s foothold heights. COP area integrated by ML-COP and AP-COP showed increasing trend due to increase of the moved trace of COP on the direction of ML and AP for posture control after landing according to truck’s foothold heights. The stability index by DPSI method (Maximum force on 3 direction GRF [ML, AP, and V] divided by elapsed time) which can be evaluated in dynamic situation meant improved higher stability index when coming to close to 0 value in each direction, but the higher index value meant lowering stability index (Wikstrom et al., 2005). Decrease of stability meant the type occurring stronger impulse force during shorter time than that of landing of foot. MLSI, APSI, VSI, and DPSI of the study showed the higher foothold height and interrupted visual information, the more decrease in stability.
When comparing of 2 variables, due to increase of impact types (PVF, loading rate) during landing on solid ground condition, increase of COP area also assumes to be correlated with equilibrium and movement of COG. whereas COP variables compared with interrupted visual information as main effector did not show difference, show more reduced COP area in case of 1st, 2nd, 3rd stair and showed rapid increasing trend in case of driver seat than noninterrupted visual information.
Predictable ability of an estimating time getting into contact with ground surface of foot through visual information on the landing height during downward stepping is critical factor to reduction of impulse force (Santello et al., 2001; Santello and McDonagh, 1998). In fact, it was reported that occurrence time of impulse force after landing was shorter than reaction time of muscle to sensory signal during absorbing an impulse (Nigg and Liu, 1999). Therefore it was assumed that reduction of DPSI according to increase of foothold height of truck was related with the failure of sufficient time securement for posture control during landing on ground (Brazen et al., 2010; Zhou et al., 1998).
Furthermore interrupted visual condition of the study influenced on the increasing trend of stability index (MLSI, APSI, VSI, and DPSI) and rapid increasing trend of COP area (ML, AP, and area), but increase of COP area should done because of difficulty of stability securement during short time of landing, also it might result in failure of posture control against increase of vertical load. Particularly because prediction of falling injury with COP variables (Maki et al., 1994), downward stepping from 2nd, 3rd stair and jumping directly from driver seat in situation of interrupted-visual information may be cause of secondary falling injury.
Because threshold level of leg stiffness may differentiate from an individual traits and ground conditions, its absolute criterion may not fix, but injury may occur whenever too low or high of it normally (Butler et al., 2003). Driver’s habit confirming the spatial information against landing position during downward stepping from truck time enables to control properly the leg stiffness and PVF with preparatory prediction of air phase time and control of impulse force. Consequently the result of the study will be helpful to not only therapist of exercise rehabilitation but availability on diagnosis, evaluation, prediction, and types of impulse-falling injury-skeletal fracture.



No potential conflict of interest relevant to this article was reported.


This work was supported by the Ministry of Education of the Republic of Korea and the National Research Foundation of Korea (NRF-2016S1A5B5A07915699).


Alexander RM. Optimization and gaits in the locomotion of vertebrates. Physiol Rev. 1989;69:1199–1227.
crossref pmid

Andrusaitis SF, Oliveira RP, Barros Filho TE. Study of the prevalence and risk factors for low back pain in truck drivers in the state of São Paulo, Brazil. Clinics (Sao Paulo). 2006;61:503–510.
crossref pmid pdf

Arampatzis A, Brüggemann GP, Metzler V. The effect of speed on leg stiffness and joint kinetics in human running. J Biomech. 1999;32:1349–1353.
crossref pmid

Bovenzi M, Hulshof CT. An updated review of epidemiologic studies on the relationship between exposure to whole-body vibration and low back pain (1986–1997). Int Arch Occup Environ Health. 1999;72:351–365.
crossref pmid

Bovenzi M, Rui F, Negro C, Agostin F, Angotzi G, Bianchi S, Bramanti L, Festa G, Gatti S, Pinto L, Rondina L, Stacchini N. An epidemiological study of low back pain in professional drivers. J Sound Vib. 2006;289:514–539.

Brazen DM, Todd MK, Ambegaonkar JP, Wunderlich R, Peterson C. The effect of fatigue on landing biomechanics in single-leg drop landings. Clin J Sport Med. 2010;20:286–292.
crossref pmid

Butler RJ, Crowell HP 3rd, Davis IM. Lower extremity stiffness: implications for performance and injury. Clin Biomech (Bristol, Avon). 2003;18:511–517.
crossref pmid

Coggon D, Croft P, Kellingray S, Barrett D, McLaren M, Cooper C. Occupational physical activities and osteoarthritis of the knee. Arthritis Rheum. 2000;43:1443–1449.
crossref pmid

Delp SL, Loan JP, Hoy MG, Zajac FE, Topp EL, Rosen JM. An interactive graphics-based model of the lower extremity to study orthopaedic surgical procedures. IEEE Trans Biomed Eng. 1990;37:757–767.
crossref pmid

Diss CE. The reliability of kinetic and kinematic variables used to analyse normal running gait. Gait Posture. 2001;14:98–103.
crossref pmid

Donelan JM, Kram R. Exploring dynamic similarity in human running using simulated reduced gravity. J Exp Biol. 2000;203:Pt 16. 2405–2415.

Dutto DJ, Smith GA. Changes in spring-mass characteristics during treadmill running to exhaustion. Med Sci Sports Exerc. 2002;34:1324–1331.
crossref pmid

Farley CT, Glasheen J, McMahon TA. Running springs: speed and animal size. J Exp Biol. 1993;185:71–86.

Farley CT, González O. Leg stiffness and stride frequency in human running. J Biomech. 1996;29:181–186.
crossref pmid

Fathallah FA, Cotnam JP. Maximum forces sustained during various methods of exiting commercial tractors, trailers and trucks. Appl Ergon. 2000;31:25–33.
crossref pmid

Feehery RV Jr. The biomechanics of running on different surfaces. Clin Podiatr Med Surg. 1986;3:649–659.

Hargrave MD, Carcia CR, Gansneder BM, Shultz SJ. Subtalar pronation does not influence impact forces or rate of loading during a single-leg landing. J Athl Train. 2003;38:18–23.
pmid pmc

Hedberg GE. Physical strain in Swedish lorry drivers engaged in the distribution of goods. J Hum Ergol (Tokyo). 1985;14:33–40.
crossref pmid

Hewett TE, Lindenfeld TN, Riccobene JV, Noyes FR. The effect of neuromuscular training on the incidence of knee injury in female athletes. A prospective study. Am J Sports Med. 1999;27:699–706.
crossref pmid

Hulshof C, van Zanten BV. Whole-body vibration and low-back pain. A review of epidemiologic studies. Int Arch Occup Environ Health. 1987;59:205–220.
crossref pmid

Hyun SH, Ryew CC. A comparison of ground reaction force components according to the foothold heights in 16-t truck during downward step. J Exerc Rehabil. 2017;13:722–727.
crossref pmid pmc pdf

Hyun SH, Ryew CC. Investigation of the ground reaction force parameters according to the shoe’s heel heights and landing distance during downward stairs on bus. Korean J Sport Biomech. 2014;24:151–160.
crossref pdf

Kapteyn TS, Bles W, Njiokiktjien CJ, Kodde L, Massen CH, Mol JM. Standardization in platform stabilometry being a part of posturography. Agressologie. 1983;24:321–326.

Kerdok AE, Biewener AA, McMahon TA, Weyand PG, Herr HM. Energetics and mechanics of human running on surfaces of different stiffnesses. J Appl Physiol (1985). 2002;92:469–478.
crossref pmid

Koh YC, Cho JH, Moon GS, Lee HD, Lee SC. Effects of visual information blockage on landing strategy during drop landing. Korean J Sport Biomech. 2011;21:31–38.
crossref pdf

Krause N, Ragland DR, Greiner BA, Fisher JM, Holman BL, Selvin S. Physical workload and ergonomic factors associated with prevalence of back and neck pain in urban transit operators. Spine (Phila Pa 1976). 1997;22:2117–2126.
crossref pmid

Kuitunen S, Komi PV, Kyröläinen H. Knee and ankle joint stiffness in sprint running. Med Sci Sports Exerc. 2002;34:166–173.
crossref pmid

Kuo AD. An optimal control model for analyzing human postural balance. IEEE Trans Biomed Eng. 1995;42:87–101.
crossref pmid

Kuo AD, Zajac FE. Human standing posture: multi-joint movement strategies based on biomechanical constraints. Prog Brain Res. 1993;97:349–358.
crossref pmid

Maetzel A, Mäkelä M, Hawker G, Bombardier C. Osteoarthritis of the hip and knee and mechanical occupational exposure--a systematic overview of the evidence. J Rheumatol. 1997;24:1599–1607.

Maki BE, Holliday PJ, Topper AK. A prospective study of postural balance and risk of falling in an ambulatory and independent elderly population. J Gerontol. 1994;49:M72–84.
crossref pmid pdf

McMahon TA, Cheng GC. The mechanics of running: how does stiffness couple with speed? J Biomech. 1990;23: Suppl 1. 65–78.
crossref pmid

McMahon TA, Valiant G, Frederick EC. Groucho running. J Appl Physiol (1985). 1987;62:2326–2337.
crossref pmid

McNitt-Gray JL. Kinetics of the lower extremities during drop landings from three heights. J Biomech. 1993;26:1037–1046.
crossref pmid

Nigg BM, Bahlsen HA, Luethi SM, Stokes S. The influence of running velocity and midsole hardness on external impact forces in heel-toe running. J Biomech. 1987;20:951–959.
crossref pmid

Nigg BM, Liu W. The effect of muscle stiffness and damping on simulated impact force peaks during running. J Biomech. 1999;32:849–856.
crossref pmid

Plagenhoef S, Evans FG, Abdelnour T. Anatomical data for analyzing human motion. Res Q Exerc Sport. 1983;54:169–178.

Rossignol M, Leclerc A, Hilliquin P, Allaert FA, Rozenberg S, Valat JP, Avouac B, Coste P, Savarieau B, Fautrel B. Primary osteoarthritis and occupations: a national cross sectional survey of 10,412 symptomatic patients. Occup Environ Med. 2003;60:882–886.
crossref pmid pmc

Ryew CC, Hyun SH. The kinetic comparison analysis of gait posture on the bus downward stair according to shoe’s heel and stair heights in the women. Korean J Phys Edu. 2013;52:523–536.

Sandmark H, Hogstedt C, Vingård E. Primary osteoarthrosis of the knee in men and women as a result of lifelong physical load from work. Scand J Work Environ Health. 2000;26:20–25.
crossref pmid

Santello M, McDonagh MJ. The control of timing and amplitude of EMG activity in landing movements in humans. Exp Physiol. 1998;83:857–874.
crossref pmid

Santello M, McDonagh MJ, Challis JH. Visual and non-visual control of landing movements in humans. J Physiol. 2001;537:Pt 1. 313–327.
crossref pmid pmc

Seidel H. Selected health risks caused by long-term, whole-body vibration. Am J Ind Med. 1993;23:589–604.
crossref pmid

Seyfarth A, Geyer H, Günther M, Blickhan R. A movement criterion for running. J Biomech. 2002;35:649–655.
crossref pmid

Sidaway B, McNitt-Gray J, Davis G. Visual timing of muscle preactivation in preparation for landing. Ecol Psychol. 1989;1:253–264.

Silder A, Besier T, Delp SL. Running with a load increases leg stiffness. J Biomech. 2015;48:1003–1008.
crossref pmid

Stefanyshyn DJ, Nigg BM. Dynamic angular stiffness of the ankle joint during running and sprinting. J Appl Biomech. 1998;14:292–299.
crossref pmid

van der Beek AJ. World at work: truck drivers. Occup Environ Med. 2012;69:291–295.
crossref pmid

van der Beek AJ, Frings-Dresen MH, van Dijk FJ, Kemper HC, Meijman TF. Loading and unloading by lorry drivers and musculoskeletal complaints. Int J Ind Ergon. 1993;12:13–23.

Wikstrom EA, Tillman MD, Smith AN, Borsa PA. A new force-plate technology measure of dynamic postural stability: the dynamic postural stability index. J Athl Train. 2005;40:305–309.
pmid pmc

Zhou S, Carey MF, Snow RJ, Lawson DL, Morrison WE. Effects of muscle fatigue and temperature on electromechanical delay. Electromyogr Clin Neurophysiol. 1998;38:67–73.

Fig. 1
Experiment field and cargo truck.
Fig. 2
Marker attachment point.
Fig. 3
Performed descending motions of 4 types.
Table 1
Change of leg stiffness and kinetic variables during downward step in cargo truck
Section Visual conditions (V) Descending type (D) Total average Source F P-value

1st foothold 2nd foothold 3rd foothold Driver’s seat
Leg stiffness (dimensionless) Open 36.20±10.39 58.56±11.00 71.02±7.86 83.33±9.74 62.28±20.00 D 47.943 0.001
Closed 57.51±8.26 69.01±6.54 79.47±12.63 92.32±18.68 74.58±17.68 V 24.259 0.001
Total average 46.86±14.25 63.79±10.31 75.24±11.12 87.83±15.22 68.43±19.75 D×V 1.475 0.109

Peak vertical force (N/BW) Open 1.87±0.63 3.28±1.12 4.95±1.56 7.57±2.48 4.42±2.64 D 24.798 0.001
Closed 3.04±0.99 4.35±2.07 6.27±2.11 9.59±2.78 5.81±3.20 V 30.668 0.001
Total average 2.45±1.00 3.81±1.71 5.61±1.92 8.57±2.76 5.11±3.00 D×V 0.723 0.545

Loading rate (N/BW/sec) Open 30.84±15.84 58.03±29.64 127.56±55.06 239.06±64.11 113.87±92.43 D 16.767 0.001
Closed 69.28±29.80 155.20±169.68 200.44±107.83 270.77±124.53 173.92±136.36 V 10.080 0.003
Total average 50.05±30.46 106.61±128.60 164.00±91.32 254.91±97.76 143.89±119.62 D×V 0.655 0.585

Values are presented as mean±standard deviation.

D, main effect of the descending types; V, main effect of the visual conditions; D×V, interaction; BW, body weight.

Table 2
Change of center of pressure (COP) variables during downward step in cargo truck
Section Visual conditions (V) Descending type (D) Total average Source F P-value

1st foothold 2nd foothold 3rd foothold Driver’s seat
Medial-lateral COP (cm) Open 1.47±0.52 1.94±0.93 2.50±1.80 2.37±0.83 2.07±1.14 D 4.439 0.009
Closed 1.14±0.89 1.81±0.55 1.83±0.57 2.43±0.67 1.80±0.80 V 1.993 0.167
Total average 1.30±0.73 1.88±0.69 2.16±1.34 2.40±0.74 1.94±0.99 D×V 0.686 0.567

Anterior-posterior COP (cm) Open 10.80±7.97 8.75±2.38 9.48±3.28 10.88±3.71 9.98±4.74 D 2.916 0.047
Closed 7.45±2.67 7.71±2.68 8.38±2.96 13.16±4.40 9.20±3.91 V 0.815 0.373
Total average 9.17±6.02 8.23±2.52 8.93±3.09 12.02±4.13 9.59±4.33 D×V 1.741 0.176

COP area (cm2) Open 12.38±3.66 15.71±5.38 19.27±7.99 24.23±9.61 17.90±8.10 D 27.800 0.001
Closed 8.82±8.75 13.34±4.71 14.42±4.95 30.14±4.86 16.68±10.02 V 0.590 0.448
Total average 10.60±6.78 14.53±5.07 16.85±6.93 27.18±8.01 17.29±9.07 D×V 2.343 0.089

Values are presented as mean±standard deviation.

D, main effect of the descending types; V, main effect of the visual conditions; D×V, interaction.

Table 3
Change of dynamic posture stability index during downward step in cargo truck
Section Visual conditions (V) Descending type (D) Total average Source F P-value

1st foothold 2nd foothold 3rd foothold Driver’s seat
Medial lateral stability index Open 1.33±1.04 1.74±1.17 3.13±1.41 12.94±8.87 4.78±6.51 D 20.446 0.001
Closed 2.05±1.58 5.22±9.61 8.02±4.99 16.08±5.99 7.84±7.98 V 6.649 0.014
Total average 1.63±1.35 3.48±6.89 5.57±4.36 14.51±7.54 6.31±7.39 D×V 36.000 0.664

Anterior posterior stability index Open 2.76±2.79 3.94±1.63 8.11±5.18 28.56±11.83 10.84±12.34 D 39.575 0.001
Closed 6.86±2.78 8.24±8.24 16.13±9.45 35.09±15.94 16.58±15.05 V 9.334 0.004
Total average 4.81±3.43 6.09±6.19 12.12±8.48 31.83±14.07 13.71±13.98 D×V 0.249 0.861

Vertical stability index Open 24.28±14.26 37.33±17.80 71.31±25.28 138.05±45.61 67.74±52.34 D 19.174 0.001
Closed 38.20±21.05 81.88±77.37 105.65±67.75 167.36±79.82 98.27±79.10 V 7.931 0.008
Total average 31.24±18.90 59.61±59.45 88.48±52.79 152.71±65.03 83.01±68.39 D×V 0.346 0.792

Dynamic posture stability index Open 28.38±17.16 43.02±20.20 82.56±29.80 179.56±61.74 83.38±69.37 D 24.615 0.001
Closed 47.12±24.33 95.36±90.15 129.80±75.41 218.53±100.48 122.70±98.38 V 8.801 0.005
Total average 37.75±22.63 69.19±69.02 106.18±60.84 199.05±83.59 103.04±86.86 D×V 0.311 0.817

Values are presented as mean±standard deviation.

D, main effect of the descending types; V, main effect of the visual conditions; D×V, interaction.

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