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RESEARCH PRODUCT
Plantar flexor activation capacity and H reflex in older adults: adaptations to strength training.
Gil ScaglioniAlessandro SartorioMarco V. NariciAlberto E. MinettiAlain MartinAlessandra FerriAlessandra FerriJ. Van HoeckePaolo Capodagliosubject
MaleVolitionAgingPhysiologydegenerationadaptationIsometric exerciseNerve conduction velocityhuman experimentH-ReflexTriceps surae muscleTwitch interpolationadaptation; aged; aging; article; controlled study; degeneration; excitability; exercise; Hoffmann reflex; human; human experiment; male; muscle contraction; muscle isometric contraction; muscle relaxation; muscle twitch; nerve conduction; normal human; plantaris muscle; priority journal; reflex arc; strength; torque; training; voluntary movement; Aging; Exercise; Triceps surae; Twitch interpolationAged 80 and overtrainingvoluntary movementReflex arcarticlereflex arcmusculoskeletal systemAdaptation Physiologicalmuscle twitchmedicine.anatomical_structuremuscle relaxationpriority journalCardiologyTriceps suraemedicine.symptomstrengthMuscle contractionMuscle Contractionmedicine.medical_specialtyWeight Liftingplantaris muscleStrength trainingPhysical exercisePhysical medicine and rehabilitationPhysiology (medical)Internal medicineexcitabilitymedicineHumanscontrolled studyhumannormal humanMuscle SkeletalExercisenerve conductionAgedmuscle isometric contractionbusiness.industrybody regionsHoffmann reflexTorqueH-reflexbusinessdescription
The purpose of this study was to investigate whether the voluntary neural drive and the excitability of the reflex arc could be modulated by training, even in old age. To this aim, the effects of a 16-wk strengthening program on plantar flexor voluntary activation (VA) and on the maximum Hoffman reflex (Hmax)-to-maximum M wave (Mmax) ratio were investigated in 14 elderly men (65–80 yr). After training, isometric maximum voluntary contraction (MVC) increased by 18% ( P < 0.05) and weight-lifting ability by 24% ( P < 0.001). Twitch contraction time decreased by 8% ( P < 0.01), but no changes in half relaxation time and in peak twitch torque were observed. The VA, assessed by twitch interpolation, increased from 95 to 98% ( P < 0.05). Pretraining VA, also evaluated from the expected MVC for total twitch occlusion, was 7% higher ( P < 0.01) than MVC. This discrepancy persisted after training. The interpolated twitch torque-voluntary torque relationship was fitted by a nonlinear model and was found to deviate from linearity for torque levels >65% MVC. Compared with younger men (24–35 yr), the Hmax- to Mmax ratio and nerve conduction velocity (H index) of the older group were significantly lower (42%, P < 0.05; and 29%, P < 0.001, respectively) and were not modulated by training. In conclusion, older men seem to preserve a high VA of plantar flexors. However, the impaired functionality of the reflex pathway with aging and the lack of modulation with exercise suggest that the decrease in the Hmax- to Mmaxratio and H index may be related to degenerative phenomena.
| year | journal | country | edition | language |
|---|---|---|---|---|
| 2002-06-01 | Journal of applied physiology (Bethesda, Md. : 1985) |