title: Neuromuscular mechanics and hopping training in elderly.
abstract: OBJECTIVE
  The present study examined the effects of repetitive hopping training on muscle activation profiles and fascicle-tendon interaction in the elderly.
  
  
  METHODS
  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.
  
  
  RESULTS
  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.
  
  
  CONCLUSIONS
  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.
authors.affiliation: Department of Biology of Physical Activity, Neuromuscular Research Center, University of Jyväskylä, Jyväskylä, Finland, merja.hoffren@jyu.fi.
authors.forename: Merja
authors.initials: M
authors.lastname: Hoffrén-Mikkola
authors.forename: Masaki
authors.initials: M
authors.lastname: Ishikawa
authors.forename: Timo
authors.initials: T
authors.lastname: Rantalainen
authors.forename: Janne
authors.initials: J
authors.lastname: Avela
authors.forename: Paavo V
authors.initials: PV
authors.lastname: Komi
mesh_terms: D000125:Achilles Tendon / Q000502:physiology*; D000368:Aged; D000843:Ankle Joint / Q000502:physiology*; D001696:Biomechanical Phenomena / Q000502:physiology; D004576:Electromyography; D015444:Exercise / Q000502:physiology*; D006801:Humans; D008297:Male; D009119:Muscle Contraction / Q000502:physiology*; D018482:Muscle, Skeletal / Q000502:physiology*