Journal of Applied Biomechanics最新文献

Repetitive manual labor tasks involving twisting, bending, and lifting commonly lead to lower back and knee injuries in the workplace. To identify tasks with high injury risk, we recruited N = 9 participants to perform industry-relevant, 2-handed lifts with a 11-kg weight. These included symmetrical/asymmetrical, ascending/descending lifts that varied in start-to-end heights (knee-to-waist and waist-to-shoulder). We used a data-driven musculoskeletal model that combined force and motion data with a muscle activation-informed solver (OpenSim, CEINMS) to estimate 3-dimensional internal joint contact forces (JCFs) in the lower back (L5/S1) and knee. Symmetrical lifting resulted in larger peak JCFs than asymmetrical lifting in both the L5/S1 (+20.2% normal [P < .01], +20.3% shear [P = .001], +20.6% total [P < .01]) and the knee (+39.2% shear [P = .001]), and there were no differences in peak JCFs between ascending versus descending motions. Below-the-waist lifting generated significantly greater JCFs in the L5/S1 and knee than above-the-waist lifts (P < .01). We found a positive correlation between knee and L5/S1 peak total JCFs (R2 = .60, P < .01) across the task space, suggesting motor coordination that favors sharing of load distribution across the trunk and legs during lifting.

The metabolic cost of walking for individuals with transtibial amputation is generally greater compared with able-bodied individuals. One aim of powered prostheses is to reduce metabolic deficits by replicating biological ankle function. Individuals with transtibial amputation can activate their residual limb muscles to volitionally control bionic ankle prostheses for walking; however, it is unknown how myoelectric control performs outside the laboratory. We recruited 6 individuals with transtibial amputation to walk an outdoor course with the Open Source Leg prosthesis under continuous proportional myoelectric control and compared it with their passive device. There were no significant differences (P = .142) in cost of transport between prostheses. Participants significantly increased residual limb vastus lateralis (P = .042) and rectus femoris (P = .029) muscle activity during early and midstance phase of walking with the powered prosthesis compared with their passive device. All but one participant preferred walking with myoelectric control compared with their passive prosthesis. The additional mass of the powered ankle prosthesis coupled with increased residual quadriceps activity could explain why the energy cost of walking was not lower compared with a passive prosthesis. This study demonstrates participants can volitionally control a bionic ankle prosthesis to navigate real-world environments.

Middle-age and older runners demonstrate differences in running biomechanics compared with younger runners. Female runners demonstrate differences in running biomechanics compared with males, and females experience hormonal changes during menopause that may also affect age-related changes in running biomechanics. The purpose of this study was to determine the relationship between age and running biomechanics in healthy female recreational runners. Fifty-two participants (ages 27-65 y) ran on an instrumented treadmill at 2 different self-selected speeds: easy pace and 5 km race pace. Lower-extremity kinematic and kinetic variables were calculated from 14 consecutive strides. Linear regression was used to determine the relationship between age and lower-extremity running biomechanics, controlling for self-selected running speed. There was a negative relationship between age and easy pace (R = -.49, P < .001) and age and 5 km race pace (R = -.43, P = .001). After controlling for self-selected running speed, there were no significant relationships between age and running biomechanics for either running speed. Several biomechanical variables were moderately to strongly correlated with running speed. Running speed should be considered when investigating age-related differences in running biomechanics.

Gait abnormalities affect an individual's ability to navigate the world independently and occur in 10% of older adults. Examining age-related gait symmetry in nonlaboratory environments is necessary for understanding mobility limitations in older adults. This study examined gait symmetry differences between older and younger adults using in-shoe force sensors. Walking trials were performed at a preferred speed. This is a secondary analysis of data from different studies in which young adults completed 7 trials and older adults completed 3 trials to decrease the impact of fatigue on outcomes in the clinical trial. Peak weight acceptance, mid stance trough, peak push-off, stance time, and impulse were collected during each step within a trial. Symmetry was determined using the absolute symmetry index. A linear mixed effects model showed a significant difference in peak weight acceptance force (P = .039), mid stance trough (P < .001), and peak push-off (P = .007) symmetry between groups. These results indicate that older adults have lower symmetry in peak weight acceptance, mid stance trough, and peak push-off during gait compared with young adults. Understanding how natural loading patterns change throughout life could improve our understanding of how load and load symmetry relate to mobility impairments in older adults.

This study compares joint kinematics and kinetics of young stroke survivors who walk <0.79 m/s (slow) or >0.80 m/s (fast) with reference to a healthy able-bodied group and provides clinical recommendations for guiding the gait rehabilitation of stroke survivors. Twenty-two young stroke survivors (18-55 y) were recruited from 6 hospital sites in the United Kingdom. Stroke participants were classified by walking speed as slow (<0.79) or fast (>0.80 m/s), and joint kinematics and kinetics at the pelvis, hip, knee, and ankle were measured during walking on level ground at self-selected speed. Ten walking biomechanical parameters correlated to walking speed (ρ ≥ .550). Stroke survivors in the slow group walked with significantly greater range of sagittal plane pelvic motion (P < .009), reduced range of hip adduction and abduction (P < .011), and smaller peak hip extension angle (P < .011) and hip flexion moment (P < .029) for the paretic limb. For the nonparetic limb, a significantly reduced hip flexion moment (P < .040) was observed compared with the fast group and control. We are the first to report how biomechanical function during walking is compromised in young stroke survivors classified by walking speed as slow (<0.79 m/s) or fast (>0.80 m/s) and propose that these biomechanical parameters be used to inform rehabilitation programs to improve walking for stroke survivors.

Rock climbing is a growing sport at both professional and recreational levels. Rock climbing requires specific hand positions with high force outputs to adapt to changing terrain requirements. The purpose of this study was to explore associations between years of climbing experience, the frequency of training, and skill level on force production in 2 different climbing-specific hand positions. A secondary purpose was to investigate sex differences in force output across climbing skill levels. Forty-nine participants ranging from Beginner to Expert skill participated. Maximum isometric pull force was tested in half-crimp and open-hand positions. Force output was larger in half-crimp versus open-hand positions. Higher skill, years of experience, and training frequency were all significantly correlated to greater force output in both hand positions. There were no force differences between males and females for Beginner/Intermediate and Advanced levels; however, males had higher force than females for Expert groups. These findings provide insight for athletes, coaches, and clinicians working with climbers regarding tissue adaptations specific to climbing grip. These findings have implications for climbing-specific training, expectations for force output, injury prevention, and reliance on hand force versus climbing technique for females climbing at high levels.

Shoes or insoles embedded with carbon fiber materials to increase longitudinal stiffness have been shown to enhance running and walking performance in elite runners, and younger adults, respectively. It is unclear, however, if such stiffness modifications can translate to enhanced mobility in older adults who typically walk with greater metabolic cost of transport compared to younger adults. Here, we sought to test whether adding footwear stiffness via carbon fiber insoles could improve walking outcomes (eg, distance traveled and metabolic cost of transport) in older adults during the 6-minute walk test. 20 older adults (10 M/10 F; 75.95 [6.01] y) performed 6-minute walk tests in 3 different shoe/insole stiffnesses (low, medium, and high) and their own footwear (4 total conditions). We also evaluated participants' toe flexor strength and passive foot compliance to identify subject-specific factors that influence performance from added shoe/insole stiffnesses. We found no significant group differences in distance traveled or net metabolic cost of transport (P ≥ .171). However, weaker toe flexors were associated with greater improvement in distance traveled between the medium and low stiffness conditions (P = .033, r = -.478), indicating that individual foot characteristics may help identify potential candidates for interventions involving footwear stiffness modifications.

Knee osteoarthritis (KOA) can have more pronounced effects on joint position sense (JPS) accuracy and gait characteristics. The aim of this study is to investigate the association between lower limb JPS and different aspects of gait pattern including gait asymmetry and variability and spatiotemporal coordination in individuals with bilateral KOA. In this cross-sectional study, lower limb JPS of 43 individuals with bilateral KOA (mild and moderate) were measured. Participants' gait patterns during treadmill walking with self-selected comfortable speed were assessed. The correlations between JPS errors and gait parameters of limb with moderate KOA were analyzed. Positive relationships were found between stance time symmetry index and JPS errors of hip abduction (r = .46, P = .003), ankle plantar flexion (r = .33, P = .03), and ankle dorsiflexion (r = .33, P = .03). Positive relationship was found between single limb support time symmetry index and hip abduction JPS error (r = .41, P = .008). Significant negative associations were found between coefficient of variation of step length and JPS errors of knee extension (r = .47, P = .002) and ankle plantar flexion (r = .33, P = .003). Results did not show any significant relationship between lower limb JPS errors and walk ratio. It is likely that lower limb JPS deficits are partially responsible for some changes in gait patterns observed in individuals with bilateral KOA.