Neuromuscular mechanics and hopping training in elderly
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The present study examined the effects of repetitive hopping training on muscle activation profiles and fascicle–tendon interaction in the elderly.
20 physically active elderly men were randomly assigned for training (TG) and control groups (CG). TG performed supervised bilateral short contact hopping training with progressively increasing training volume. Measurements were performed before the training period (BEF) as well as after 2 weeks (2 W) and 11 weeks (11 W) of training. During measurements, the gastrocnemius medialis–muscle (GaM) fascicle and its outer Achilles tendon length changes during hopping were examined by ultrasonography together with electromyographic (EMG) activities of calf muscles, kinematics, and kinetics.
At 2 W, the ankle joint stiffness was increased by 21.0 ± 19.3 % and contact time decreased by 9.4 ± 7.8 % in TG. Thereafter, from 2–11 W the jumping height increased 56.2 ± 18.1 % in TG. Simultaneously, tendon forces increased 24.3 ± 19.0 % but tendon stiffness did not change. GaM fascicles shifted to shorter operating lengths after training without any changes in their length modifications during the contact phase of hopping. Normalized EMG amplitudes during hopping did not change with training.
The present study shows that 11 W of hopping training improves the performance of physically active elderly men. This improvement is achieved with shorter GaM operating lengths and, therefore, increased fascicle stiffness and improved tendon utilization after training. Based on these results, hopping training could be recommended for healthy fit elderly to retain and improve rapid force production capacity.
KeywordsStretch–shortening cycle Aging Ultrasound Electromyography Tendon Gastrocnemius medialis
Ankle joint stiffness
Achilles tendon force
Baseline (first) measurement session before training
Vertical component of the ground reaction force
Gastrocnemius lateralis muscle
Gastrocnemius medialis muscle
Ground reaction force
Knee joint stiffness
Maximal voluntary contraction
Root mean square
Reactive strength index
Tibialis anterior muscle
- 2 W
Second measurement session after 2 weeks of training
- 11 W
Third and last measurement session after 11 weeks of training
The authors acknowledge the valuable contribution of Ms. P. Puttonen and Mr Masanobu Akiyama for help with the data analysis. This study was supported by Grant #123757 from the Academy of Finland, by Finnish Cultural Foundation´s South Ostrobothnia Regional Fund´s personal grant for Merja Hoffrén-Mikkola and by the research exchange grant of Osaka University of Health and Sport Sciences. Dr Rantalainen was supported by an Alfred Deakin Postdoctoral Research Fellowship from Deakin University during the preparation of the manuscript.
Conflict of interest
The authors declare that they have no conflict of interest.
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