GREATER CROSS EDUCATION FOLLOWING TRAINING WITH MUSCLE LENGTHENING THAN SHORTENING

The hypothesis was tested that the magnitude of cross education is gre ater following training with muscle lengthening than shortening. Chang es in contralateral concentric, eccentric, and isometric strength and vastus lateralis and biceps femoris surface electromyographic (EMG) ac tivity were analyzed in groups of young men who exercised the ipsilate ral quadriceps with either eccentric (N = 7) or concentric (N = 8) con tractions for 36 sessions over 12 wk. Control subjects (N = 6) did not train. Concentric training increased concentric strength 30% and isom etric strength 22%, and eccentric training increased eccentric strengt h 77% and isometric strength 39% (all P < 0.05). Eccentric training im proved eccentric strength three times more than the concentric trainin g improved concentric strength (P < 0.05), and eccentric compared with concentric training improved isometric strength about 2 times more (P < 0.05). The eccentric group improved significantly from pre- to mid- training in eccentric and isometric strength (P < 0.05). The control g roup showed no significant changes (P < 0.05). Surface EMG activity of the vastus lateralis increased 2.2 times (pre to mid-training), 2.8 ( mid- to post-training) and 2.6 more (pre- to posttraining) (P < 0.05) in the eccentric than concentric group. No significant changes in EMG activity occurred in the control group (P > 0.05). It was concluded th at the greater cross education following training with muscle lengthen ing is most likely being mediated by both afferent and efferent mechan isms that allow previously sedentary subjects to achieve a greater act ivation of the untrained limb musculature.