The Lower Limb Stiffness, Moments, and Work Mode During Stair Descent Among the Older Adults

OBJECTIVE

Lower limb stiffness strategies and work mode changes between young and older adults during stair descent are unclear. This study investigated the effect of aging on the lower limb stiffness, moments, and joint work mode during stair descent.

DESIGN

Twenty young adults and 20 older adults were recruited from the local community for stair descent test. Kinematics and kinetics data were collected by Vicon system and Kistler force plate. The lower limb stiffness, moments, and work mode were calculated and assess between groups.

RESULTS

No significant differences in gait parameters were detected between groups. Compared with young adults, older adults have decreased leg stiffness, knee and ankle stiffness, increased peak hip extension moment, hip stiffness, and ankle work contribution.

CONCLUSIONS

The older adults actively reduce the lower limb stiffness to reduce the risk of injury during stair descent. The hip joint strategy reduces the risk of forwarding falls and ankle joint compensation work mode to make up for the lack of knee extension strength. This provides a reference for the focus of exercise intervention and rehabilitation strategies for older adults.

Variations in lower body stiffness during sports-specific tasks in well-trained female athletes

The present study aimed to assess the differences in leg stiffness and the associated performance variables between athletes from various training backgrounds during tasks relevant to athletic training. Forty-seven female participants (20 nationally identified netballers, 13 high-level endurance athletes and 14 age-matched controls) completed a sprint, anticipated sidestep change of direction and unilateral repetitive hopping task to assess leg stiffness and the relationship of stiffness between the different tasks. Leg stiffness and performance variables were evaluated with a 10-camera motion analysis system and force plate, and leg stiffness was derived through the McMahon and Cheng methodology (1990). Significant differences were evident in leg stiffness, and the contributing performance variables between groups across all assessed tasks (p < 0.001-0.017). Furthermore, results indicated the control group displayed no leg stiffness relationship between the evaluated tasks, while the stiffness relationship between tasks within athletic populations reflected training-specific demands of athletes. The results of this study indicated that the athletic training background of individuals may contribute to inherent leg stiffness differences between groups. Furthermore, the stiffness relationship observed between tasks suggests practitioners should take care in the selection of task used to monitor leg stiffness from a performance or injury risk perspective.

A comparison of lower limb stiffness and mechanical muscle function in ACL-reconstructed, elite, and adolescent alpine ski racers/ski cross athletes

PURPOSE

The aim of this study was to compare mechanical muscle function in the eccentric/concentric phases of vertical bilateral jumping in anterior cruciate ligament-reconstructed (ACLR), elite (ELITE), and adolescent (ADOL) alpine ski racers and ski cross athletes.

METHODS

Alpine ski racers/ski crossers (ACLR: n = 12, age = 26.7 ± 3.8 years; ELITE: n = 12, age = 23.9 ± 3.0 years; ADOL: n = 12, age = 17.8 ± 0.7 years; females: n = 6 per group, males: n = 6 per group) performed 5 maximal countermovement jumps (CMJs) and 5 squat jumps. The ground reaction forces for each limb were analyzed using dual force plate recording to obtain body center of mass (BCM) velocity, displacement, and power. The eccentric deceleration (ECC) and concentric phases were determined from BCM velocity. CMJ net concentric and ECC impulses were calculated (body mass normalized) along with the peak and mean BCM power and maximal vertical jump height. CMJ lower limb stiffness (LLS) was determined by the slope of the ground reaction forces vs. the BCM displacement curve over the ECC phase. Concentric and ECC asymmetry indices were calculated for each leg, and the left vs. right LLS was compared. Outcome measures (reported as mean ± SD) calculated as a 5-jump mean were normalized to body mass and compared using an analysis of variance.

RESULTS

No between-group differences were found for peak and mean power or jump heights. There were no group differences for LLS or net concentric phase impulse, but the net ECC impulse was lower in the ADOL group compared with ELITE skiers (ADOL: 1.33 ± 0.32 Ns/kg; ELITE: 1.59 ± 0.16 Ns/kg; p < 0.05). Although no group differences were found for ECC asymmetry indices, a group × limb interaction was found for LLS (p < 0.01), which was systematically higher in the right vs. the left limb of ADOL skiers (right: 54.1 ± 17.9 N/m/kg; left: 48.7 ± 15.7 N/m/kg; p < 0.01).

CONCLUSION

ADOL skiers demonstrated decreased ECC impulse and systematic right limb dominance in LLS compared with ACLR and ELITE skiers. The implication of these findings for injury and performance are unknown, but further investigation into these potential relationships is warranted.