It is unknown if forward trunk lean during single-limb landing influences the Achilles tendon force (ATF). This study examined the effect of forward trunk lean during single-limb landing on the ATF in physically active f...It is unknown if forward trunk lean during single-limb landing influences the Achilles tendon force (ATF). This study examined the effect of forward trunk lean during single-limb landing on the ATF in physically active females. Thirty physically active females (23.7 [3.6] y) performed 5 landing trials (0.25 m) using self-selected and forward trunk lean strategies. Dependent variables included peak ATF; average ATF development rate; and sagittal trunk, hip, knee, and ankle angles and moments at the time of peak ATF. The increased forward trunk lean (mean difference (MD) = 14.1°; 95% CI, 11.0 to 17.2; P < .001) caused a decrease in peak ATF (MD = -3.5 N/kg; 95% CI, -5.8 to -1.2; P = .004) and ankle plantar flexion moment (MD = -0.2 N·m/kg; 95% CI, -0.4 to -0.1; P = .002). In contrast, forward trunk lean resulted in greater hip (MD = 15.2°; 95% CI, 11.9 to 18.4; P < .001) and knee flexion (MD = 7.7°; 95% CI , 4.7 to 10.7; P < .001) angles, and hip extension moment (MD = 0.3 N·m/kg; 95% CI, 0.1 to 0.5; P = .002). Forward trunk lean changes predicted peak ATF changes (r = .33, P = .04). Sagittal trunk posture influences the ATF in physically active females during single-limb landing and may effectively alter loading in patients recovering from Achilles tendinopathy.
To increase understanding in development of running injuries, the biomechanical load over time should be studied. Ground reaction force (GRF) is an important parameter for biomechanical analyses and is typically measured...To increase understanding in development of running injuries, the biomechanical load over time should be studied. Ground reaction force (GRF) is an important parameter for biomechanical analyses and is typically measured in a controlled lab environment. GRF can be estimated outdoors, however, the repeatability of this estimation is unknown. Repeatability is a crucial aspect if a measurement is repeated over prolonged periods of time. This study investigates the repeatability of a GRF estimation algorithm using inertial measurement units during outdoor running. Twelve well-trained participants completed 3 running sessions on different days, on an athletics track, instrumented with inertial measurement units on the lower legs and pelvis. Vertical accelerations were used to estimate the GRF. The goal was to assess the algorithm's repeatability across 3 sessions in a real-world setting, aiming to bridge the gap between laboratory and outdoor measurements. Results showed a good level of repeatability, with an intraclass correlation coefficient (2, k) of .86 for peak GRF, root mean square error of .08 times body weight (3.5%) and Pearson correlation coefficients exceeding .99 between the days. This is the first study looking into the day-to-day repeatability of the estimation of GRF, showing the potential to use this algorithm daily.
The calf raise test (CRT) is commonly used to assess triceps surae muscle-tendon unit function. Often, a metronome set to 60 beats/min (30 repetitions/min) is used to set the cadence of calf raise repetitions, but studie...The calf raise test (CRT) is commonly used to assess triceps surae muscle-tendon unit function. Often, a metronome set to 60 beats/min (30 repetitions/min) is used to set the cadence of calf raise repetitions, but studies report using cadences ranging from 30 to 120 beats/min. We investigated the effect of cadence on CRT outcomes, accounting for the potential confounders of sex, age, body mass index, and physical activity. Thirty-six healthy individuals (50% female) performed single-leg calf raise repetitions to volitional exhaustion in 3 randomized cadence conditions, 7 days apart: 30, 60, and 120 beats/min. Repetitions, total vertical displacement, total work, peak height, and peak power were recorded using the validated Calf Raise application. Cadence significantly affected all CRT outcomes (P ≤ .008), except repetitions (P = .200). Post hoc analysis revealed 60 beats/min resulted in significantly greater total vertical displacement and work than 30 and 120 beats/min. Peak height was greater at 60 and 120 than 30 beats/min, and peak power was greater at 120 beats/min. Males generated greater work and peak power (P ≤ .001), whereas individuals with greater body mass index completed less repetitions (P = .008), achieved lower total vertical displacements (P = .003), and generated greater peak power (P = .005). CRT cadence is important to consider when interpreting CRT outcomes and comparing data between studies.
In many sports, practitioners must reach their maximal jump height (hmax) under time constraints. This requires a reduction of the countermovement depth and so of the push-off distance (hPO). The purpose of this study wa...In many sports, practitioners must reach their maximal jump height (hmax) under time constraints. This requires a reduction of the countermovement depth and so of the push-off distance (hPO). The purpose of this study was to investigate how hPO influences force-velocity (F-v) profiles (F¯0, v¯0, P¯max, and SFv) and performance. Eleven participants (age: 26 [5] y, height: 175.6 [11.2] cm, mass: 76 [15] kg; squat 1RM: 129 [34] kg) performed maximal countermovement jumps. Kinetic and kinematic measurements were used to assess individual F-v profiles for 3 different hPO conditions (hPO-SMALL, hPO-MEDIUM, hPO-LARGE) from countermovement jumps performed under different load conditions (bodyweight [BW], BW + 8 kg, BW + 17 kg, BW + 40%1RM, BW + 70%1RM). Results indicated that F¯0 and P¯max changed across hPO conditions, while v¯0 remained constant. A lower hPO led to a significantly higher F¯0 and P¯max. These changes resulted in a steeper SFv leading to a more force-oriented profile, a lower optimal SFv and a greater F-v imbalance. Reducing hPO and modifying F-v profile led, to some extent, to a reduction in hmax. Performance is a compromise between hPO, P¯max, and F-v imbalance, all influenced by countermovement depth. This explains why reducing countermovement depth to meet time constraint may lower performance.
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 biologica...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.
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 i...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.
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 hormo...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 mob...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.
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 w...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.
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 asp...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.
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 th...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.
White LT, Malcolm P, Franz JR
… +1 more, Takahashi KZ
J Appl Biomech
· 2025 Apr · PMID 39753120
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Full text
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, howev...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.
The purpose of this study was to determine the role of antiphase trunk motion during quiet stance while maintaining constant visual and support surface conditions. Eyes-open quiet stance trials were performed on a firm s...The purpose of this study was to determine the role of antiphase trunk motion during quiet stance while maintaining constant visual and support surface conditions. Eyes-open quiet stance trials were performed on a firm support surface while wearing a rigid hip-knee orthotic brace that reduced antiphase trunk motion. Amplitude spectral density, coherence, and cophase were compared for hip-locked, hip-unlocked, and no-brace conditions. Amplitude spectral density calculations showed that trunk and leg sway velocities, and ankle torque (AT) decreased when antiphase trunk sway was allowed. Coherence and cophase estimates identified in-phase trunk-legs sway below 1 Hz and antiphase at higher frequencies. Legs-AT cophase calculations showed that the legs lagged the application of AT at all frequencies, while trunk-AT cophase showed the trunk lagged AT below 1 Hz and led AT at higher frequencies. The results demonstrate that antiphase trunk sway helps reduce sway velocity and AT. Furthermore, the trunk-leading cophase relationship with AT showed that antiphase trunk motion occurred before AT was applied. This implies that antiphase trunk motion facilitates changes in sway direction and helps regulate sway velocity. The results have significant implications for predicting postural control deficiencies due to injury, disease, and aging.
Reaching is a common daily activity requiring a range of humeral elevation that contributes to rotator cuff compression. The purpose of this study was to estimate supraspinatus and infraspinatus tendon compression risk r...Reaching is a common daily activity requiring a range of humeral elevation that contributes to rotator cuff compression. The purpose of this study was to estimate supraspinatus and infraspinatus tendon compression risk relative to the acromion and coracoacromial ligament during reaching by manual wheelchair users with spinal cord injury. A cross-sectional design was used to evaluate 8 participants (7 males, median [range] age 36 y [23-61]). Electromagnetic motion capture recorded shoulder kinematics while participants reached for a can at 2 heights: low (0.91 m) and high (1.37 m). Using 1 set of computed tomographic-based bone models and individual glenohumeral kinematics, compression risk was evaluated as the percentage of the reach activity and number of seconds that tendon insertions were less than 5 mm from scapular landmarks. Reach conditions were compared using a Wilcoxon signed-rank test (α = .05). Although not statistically significant, the supraspinatus and infraspinatus relative to the acromion had approximately 40% of the activity duration or 0.8 seconds more time under 5 mm in low versus high reach, indicating increased risk of compression. Compression risk estimates were consistent with prior publications on planar arm movements. Estimating the risk of tendon compression using absolute time may help with understanding cumulative exposure during day-to-day activity.
Advanced footwear technologies contain thicker, lightweight, and more resilient midsoles and are associated with improved running economy (RE) compared with traditional footwear. This effect is highly variable with some...Advanced footwear technologies contain thicker, lightweight, and more resilient midsoles and are associated with improved running economy (RE) compared with traditional footwear. This effect is highly variable with some individuals gaining a greater RE benefit, indicating that biomechanics plays a mediating role with respect to the total effect. Indeed, the energy generated by contractile elements and the elastic energy recovered from stretched tendons and ligaments in the legs and feet are likely to change with footwear. Therefore, if RE is to be maximized according to individual characteristics, an individualized approach to footwear selection is required. However, current theoretical frameworks hinder this approach. Here, we introduce a framework that describes causal relationships between footwear properties, biomechanics, and RE. The framework proposes that RE changes with footwear due to (1) a direct effect of footwear properties-for example, increased or decreased energy return-and (2) a mediating effect of footwear on ankle and foot biomechanics and the spring-mass system. By describing the total effect as 2 complementary pathways, the framework facilitates research that aims to separately quantify direct and mediating effects of footwear. This may permit the development of footwear materials that can separately target the direct and individual mediating effects.
Intramuscular (iEMG) and surface electromyographic (sEMG) signals have been compared previously using predictive regression equations, finite element modeling, and correlation and cross-correlation analyses. Although sub...Intramuscular (iEMG) and surface electromyographic (sEMG) signals have been compared previously using predictive regression equations, finite element modeling, and correlation and cross-correlation analyses. Although subcutaneous fat thickness (SCFT) has been identified as a primary source of sEMG signal amplitude attenuation and low-pass filter equivalence, few studies have explored the potential effect of SCFT on sEMG and iEMG signal characteristics. The purpose of this study was to investigate the relationship between normalized submaximal iEMG and sEMG signal amplitudes collected from 4 muscles (rectus femoris, vastus lateralis, infraspinatus, and erector spinae) and determine whether SCFT explains more variance in this relationship. The effect of sex was also explored. Linear regression models demonstrated that the relationship between sEMG and iEMG was highly variable across the muscles examined (adjusted coefficient of determination [Adj R2] = .02-.74). SCFT improved the model fit for vastus lateralis, although this relationship only emerged with the inclusion of sex as a covariate. Thus, this research suggests that SCFT is not a prominent factor affecting the linearity between sEMG and iEMG. Researchers should investigate other parameters that may affect the linearity between sEMG and iEMG signals.
Foot position during landing directly influences knee mechanics. Thus, the purpose of this study was to determine success in practicing, repeating, and transferring a desired foot progression angle (FPA) during landing,...Foot position during landing directly influences knee mechanics. Thus, the purpose of this study was to determine success in practicing, repeating, and transferring a desired foot progression angle (FPA) during landing, as well as changes in knee mechanics. Twenty females were randomly assigned to a control or verbal instruction group. On day 1, each group performed 40 drop landings. The verbal instruction group was instructed to "Land with 30 degrees of external rotation" before every trial. Feedback was provided on a terminal schedule in the form of knowledge of FPA error. On day 2, retention was assessed with 5 drop landings, while transfer was assessed during a 2-step stop-jump landing. Repeated-measures analyses of variance (2 × 4 [group × time]) were used to assess the influence of verbal instruction on knee mechanics. Participants who received verbal instruction exhibited increased FPA. They also demonstrated increased initial contact knee abduction during acquisition and retention. For all participants, initial contact knee flexion increased, while peak knee adduction moment decreased during acquisition. While the verbal instruction cue was effective in promoting an increase in FPA and reducing some ACL injury risk factors during practice and retention, this cue may only be effective to tasks similar to what was practiced.