title: Age-specific neuromuscular interaction during elderly habitual running.
abstract: OBJECTIVE
  It has been reported that advancing age causes tendons to become more compliant and fascicles length shorter. This could then lead to enhancement of movement efficiency provided that the elderly adults can activate their muscles in the same way as the younger adults (YOUNG) during dynamic movements. This study was designed to examine the age-specific behaviour of the medial gastrocnemius (MG) fascicles and tendinous tissues together with lower-leg muscle activities when the well-trained elderly runners ran on the treadmill at preferred speeds.
  
  
  METHODS
  The well-trained 11 elderly subjects (ELD) who have running experiences and 11 YOUNG were recruited as subjects. While ELD were running on the treadmill at their preferred speed, the lengths of the MG fascicles and tendinous tissues (Lfa and LTT respectively) were measured by ultrasonography together with kinematics and lower-leg muscle activities.
  
  
  RESULTS
  Although the behaviour of the MG muscle-tendon unit did not show any significant differences between both groups during the contact, our results showed significant differences in fascicle-tendinous tissue behaviour as well as muscle activities. The LTT during the entire contact phase was greater in ELD than in YOUNG (P < 0.001). Co-activation of lower-leg muscles from pre-activation to braking phases was higher in ELD than in YOUNG (P < 0.01). The changes of the Lfa during contact were less, and the LTT shortening was greater in ELD than in YOUNG (P < 0.001).
  
  
  CONCLUSIONS
  These results imply that ELD cannot activate their muscles similar to YOUNG during running, and those different activities may modify the Lfa to utilize the tendon elasticity effectively.
authors.affiliation: Osaka University of Health and Sports Sciences, Osaka, Japan.
authors.forename: K
authors.initials: K
authors.lastname: Sano
authors.affiliation: Osaka University of Health and Sports Sciences, Osaka, Japan.
authors.forename: M
authors.initials: M
authors.lastname: Akiyama
authors.affiliation: Neuromuscular Research Center, Department of Biology of Physical Activity, University of Jyväskylä, Jyväskylä, Finland.
authors.forename: M
authors.initials: M
authors.lastname: Hoffrén-Mikkola
authors.affiliation: Osaka University of Health and Sports Sciences, Osaka, Japan.
authors.forename: A
authors.initials: A
authors.lastname: Ito
authors.affiliation: Neuromuscular Research Center, Department of Biology of Physical Activity, University of Jyväskylä, Jyväskylä, Finland.|Likes Research Center, University of Jyväskylä, Jyväskylä, Finland.
authors.forename: P V
authors.initials: PV
authors.lastname: Komi
authors.affiliation: Osaka University of Health and Sports Sciences, Osaka, Japan.
authors.forename: M
authors.initials: M
authors.lastname: Ishikawa
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000375:Aging; D004576:Electromyography / Q000379:methods; D005260:Female; D006184:Habits; D006801:Humans; D007866:Leg / Q000294:innervation / Q000502:physiology; D008297:Male; D008875:Middle Aged; D009068:Movement / Q000502:physiology; D009119:Muscle Contraction / Q000502:physiology*; D018482:Muscle, Skeletal / Q000294:innervation* / Q000502:physiology*; D012420:Running / Q000502:physiology*; D013710:Tendons / Q000502:physiology; D055815:Young Adult
keywords: ageing; co-activation; locomotion; tendon; ultrasound