title: Neuromuscular and balance responses to flywheel inertial versus weight training in older persons.
abstract: OBJECTIVE
  Loss of muscle strength and balance are main characteristics of physical frailty in old age. Postural sway is associated with muscle contractile capacity and to the ability of rapidly correcting ankle joint changes. Thus, resistance training would be expected to improve not only strength but also postural balance.
  
  
  METHODS
  In this study, age-matched older individuals (69.9+/-1.3 years) were randomly assigned to flywheel (n=12), or weight-lifting (n=12) groups, training the knee extensors thrice weekly for 12 weeks. The hypotheses were that owing to a larger eccentric loading of the knee extensors, flywheel training would result in (a) greater gains in quadriceps strength; (b) greater improvements in balance performance compared with weight-lifting training. Isokinetic dynamometry, B-mode ultrasonography, electromyography, percutaneous muscle stimulation and magnetic resonance imaging were employed to acquire the parameters of interest.
  
  
  RESULTS
  Following training, knee extensors peak isokinetic power increased by 28% (P<0.01) in the flywheel group with no change in the weight-lifting group. Adaptations of the gastrocnemius muscle also occurred in both groups. The gastrocnemius characteristic with the highest response to training was tendon stiffness, with increases of 54% and 136% in the weight-lifting and flywheel groups, respectively (P<0.01). The larger increase in tendon stiffness in the flywheel group was associated with an improvement in postural balance (P<0.01).
  
  
  CONCLUSIONS
  Quadriceps flywheel loading not only produces a greater increase in power than weight training but its physiological benefits also transfer/overspill to the plantarflexor muscle-tendon unit resulting in a significantly improved balance. These findings support our initial hypotheses.
authors.affiliation: Department of Exercise and Sport Science, Manchester Metropolitan University, Hassall Road, Alsager, ST7 2HL, UK. g.pearson@mmu.ac.uk
authors.forename: Gladys L
authors.initials: GL
authors.lastname: Onambélé
authors.forename: Constantinos N
authors.initials: CN
authors.lastname: Maganaris
authors.forename: Omar S
authors.initials: OS
authors.lastname: Mian
authors.forename: Enrico
authors.initials: E
authors.lastname: Tam
authors.forename: Enrico
authors.initials: E
authors.lastname: Rejc
authors.forename: Islay M
authors.initials: IM
authors.lastname: McEwan
authors.forename: Marco V
authors.initials: MV
authors.lastname: Narici
mesh_terms: D000368:Aged; D015444:Exercise / Q000502:physiology; D006801:Humans; D007719:Knee Joint / Q000502:physiology*; D009119:Muscle Contraction / Q000502:physiology; D018482:Muscle, Skeletal / Q000502:physiology*; D005082:Physical Exertion / Q000502:physiology*; D010809:Physical Fitness / Q000502:physiology*; D004856:Postural Balance / Q000502:physiology*; D011187:Posture / Q000502:physiology*; D055070:Resistance Training / Q000379:methods*