A comprehensive assessment of the cross-training effect in ankle dorsiflexors of healthy subjects: A randomized controlled study.
OBJECTIVE
To investigate the cross-training effect, induced on ankle dorsiflexors (AD) by unilateral strength-training of the contralateral muscles, as transfer of peak torque (PT) and muscle work (MW) and their relative contributions to muscle performance.


METHODS
Thirty healthy volunteers were randomly assigned to a training or control group. The trained group sustained a 4-week maximal isokinetic training of the stronger AD at 90 and 45°/s. At both angular velocities, PT, MW and MW/PT ratio were measured from both legs at baseline and after intervention (trained group) or no-intervention (controls). The familiarization/learning-effect was calculated and subtracted by PT and MW measures to obtain their net changes.


RESULTS
Net PT increased in both legs (untrained: +27.5% at 90°/s and +17.9% at 45°/s; trained: +15% at 90°/s and +16.3% at 45°/s). Similarly, net MW increased in both the untrained (90°/s: +29.6%; 45°/s: +37%) and trained (90°/s: +23.4%; 45°/s: +18.3%) legs. PT and MW gains were larger in the untrained than trained AD (p<0.0005), with MW improving more than PT at 45°/s (p=0.04). The MW/PT ratio increased bilaterally only in the trained group (p<0.05), depending on the angular velocity.


CONCLUSIONS
The cross-training effect occurred in AD muscles in terms of both PT and MW, with MW adding valuable information to PT-analysis in describing muscle performance. Moreover, the MW/PT ratio allowed estimating the contributions of these parameters to muscle capability and may represent a novel index in isokinetic testing. The greater improvements in the untrained than trained limb raises interesting clinical implications in asymmetric conditions.
Department of Biomedical Sciences, University of Sassari, Sassari, Italy.
Andrea
A
Manca
Department of Surgical, Microsurgical and Medical Sciences, University of Sassari, Sassari, Italy.
Francesco
F
Pisanu
Neurology Unit, «A. Segni» Hospital - ASL n. 1, Sassari, Italy.
Enzo
E
Ortu
Department of Biomedical Sciences, University of Sassari, Sassari, Italy.
Edoardo Rosario
ER
De Natale
Department of Biomedical Sciences, University of Sassari, Sassari, Italy.
Francesca
F
Ginatempo
Department of Biomedical Sciences, University of Sassari, Sassari, Italy.
Daniele
D
Dragone
Department of Biomedical Sciences, University of Sassari, Sassari, Italy.
Eusebio
E
Tolu
Department of Biomedical Sciences, University of Sassari, Sassari, Italy. Electronic address: deriuf@uniss.it.
Franca
F
Deriu
D000328:Adult; D000842:Ankle / Q000502:physiology*; D005260:Female; D007839:Functional Laterality / Q000502:physiology*; D005684:Gait / Q000502:physiology; D064368:Healthy Volunteers; D006801:Humans; D008297:Male; D053580:Muscle Strength / Q000502:physiology*; D018482:Muscle, Skeletal / Q000502:physiology*; D016059:Range of Motion, Articular / Q000502:physiology*; D055070:Resistance Training / Q000379:methods*; D019415:Torque
Cross-education; Isokinetic testing; Muscle strength; Peak torque; Work