GREATER INITIAL ADAPTATIONS TO SUBMAXIMAL MUSCLE LENGTHENING THAN MAXIMAL SHORTENING

The purpose of this study was to compare the short-term strength and n eural adaptations to eccentric and concentric training at equal force levels. Forty-two sedentary women (age = 21.5 yr) were ranked based on the initial quadriceps strength score, and trios of subjects were ran domly assigned to either an eccentric (n = 14), a concentric (n = 14), or a nonexercising control group (n = 14). Training involved a total of 824 eccentric or concentric quadriceps actions at 1.05 rad . s(-1) administered in four sets of 6-10 repetitions, four times per week for 6 wk. Before and after training, all subjects were tested for unilate ral maximal isometric and eccentric and concentric actions at 1.05 rad . s(-1) and for a 40-repetition eccentric and concentric fatigue seri es of the left and right quadriceps. Surface electromyographic activit y of the vastus lateralis and medialis was monitored during testing. C oncentric training increased concentric (36%, P < 0.05), isometric (18 %, P < 0.05), and eccentric strength (13%), and eccentric training inc reased eccentric (42%, P < 0.05), isometric (30%, P < 0.05), and conce ntric (13%) strength. Eccentric training improved eccentric and isomet ric strength more (P < 0.05) than did concentric training. The electro myographic adaptations were greater with eccentric training. Cross-edu cation was 6%, and neither training mode modified fatigability. The da ta suggest that training of the quadriceps muscle with submaximal ecce ntric actions brings about greater strength adaptations faster than do es training with maximal-level concentric actions in women. This great er adaptation is likely to be mediated by both mechanical. and neural factors.