Exercise training in older people causes joint moment redistribution during stair descent.

Authors: Gavin, J.P., Reeves, N.D., Maganaris, C.N. and Baltzopolous, V.

Start date: 12 July 2015

Introduction and Objectives: Stair descent presents a physically demanding task, routine to everyday life, which is made more challenging by age-related deteriorations in lower-limb musculoskeletal capacities. Decline in functional mobility is particularly limiting in built environments, where stairs comprised of increased rise steps may be encountered. Stair descent involves mainly eccentric contractions, and with the old operating at higher maximum eccentric ankle capacities than the young [1], exercise training may allow older adults to meet the varying biomechanical demands of descent [2]. This study examined the effects of lower-limb exercise training on the biomechanics of older adults when descending standard, and increased rise stairs.

Methods: Fifteen older adults (age, 75±3 years) descended a four step stair adjusted to standard rise (170 mm), and 50% increased rise (255 mm) higher than those common to public and residential buildings [3]. Trials were on separate visits before, and after 16 weeks of either: resistance exercise and stretching training (n = 8), or no training (n = 7). Three, unaided trials were performed on each visit, at a self-selected pace. Kinematic and kinetic data were measured during a single gait cycle, referring to the left leg [4]. Kinetic data were measured from step-mounted force plates (Kistler type Z17068, Kistler Instruments, Winterthur, Switzerland), and kinematic data from motion-capture cameras at 120 Hz (VICON 612 system, VICON Motion Systems Ltd., Oxford, UK). Trials were calculated with a ‘plug-in-gait’ model, and processed by running a static and dynamic model using Workstation software (VICON Motion Systems Ltd., Oxford, UK). Training involved two sessions per week of resistance exercises (three sets of ~8 repetitions for: leg-press, knee extension and calf-press, at ~80% three-repetition maximum), and static plantarflexor stretching (45 s holds, with three repetitions per leg). Eccentric, maximum voluntary contractions of the knee extensors (angular velocities of 60, 120, 180 and 240°·s-1) and plantarflexors were assessed before, and after 16 weeks for training and control groups using an isokinetic dynamometer (Cybex NORM, New York, USA), as was maximum dorsiflexion angle. Repeated, 2 (time) x 2 (step rise) measures ANOVA compared changes after 16 weeks for both groups on standard and increased rise stairs. Bonferroni Adjustments were used to identify step rise-specific training effects in each group. Data analysis was performed using IBM SPSS Statistics Version 21 (IBM Corp, Armonk, NY), with statistical significance as 0.05.

Results: Maximum eccentric torques increased at the knee (by 29.8% at 60°·s-1 and 43.2% at 180°·s-1; P<0.001) and ankle (by 35.3% at 60°·s-1; P=0.001) after exercise training, as did maximum dorsiflexion angle. Training did not alter ankle angles when descending either stair. Training decreased knee flexion angle in single-leg stance (P=0.03) on standard stairs, and increased flexion angle upon final foot contact on increased rise stairs (P=0.001). Training did not affect hip flexion angle for either stair, but hip abduction angle increased in double support for increased rise stairs (P=0.04). Descending increased rise stairs required higher ankle and hip joint moments, and lower knee joint moments, when compared to standard stairs (P<0.001). Training reduced ankle joint moment (P<0.001), but increased knee joint moment (P=0.01), on increased rise stairs; training increased ankle joint moment (P<0.001), but reduced knee joint moment (P<0.01), on standard stairs. Training did not alter hip joint moments on increased rise stairs; upon standard stairs, hip flexion moment increased (from foot contact to double support, P<0.001) and hip abduction moment decreased (from single-leg stance to double support, P<0.05; Figure 1).

Conclusion: Older adults after training descended i) standard rise stairs, by increasing ankle and hip joint moments, and reducing knee joint moments; and ii) increased rise stairs, by increasing knee joint moments and reducing ankle joint moments. These findings suggest older adults adopt neuromuscular strategies to meet the demands of stair descent, and strength improvements from exercise training can reorganise these strategies.

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