Neuromuscular Adaptions in Isokinetic, Isotonic, and AgilityTraining Programs

Abstract

Weight training is an integral part of most athletic conditioning programs, yet the effect of these programs on neuromuscular function remains unclear. This project was designed to determine the effect of isotonic, isokinetic, and agility training on muscle reaction time. Thirty-two healthy volunteers (16 men, 16 women), with an average age of 25.4 years were placed into one of four groups: isokinetic, isotonic, agility, or control. The isokinetic protocol consisted of 3 sets of 12 repetitions of knee flexion and extension at 600 /s and 3 sets of 12 repetitions of ankle plantarflexion and dorsiflexion at the same speed. The isotonic protocol consisted of 3 sets of 12 repetitions of leg press, hamstring curls, and calf raises. The agility training protocol consisted of slideboarding, bounding on one leg, and running figure 8, carioca and backward run drills. All groups trained three days/week for six weeks. All participants underwent KT-1000 Arthrometer measurements, isokinetic strength and endurance tests, and EMG monitored muscle response tests to induce anterior tibial displacement. Five lower extremity muscle groups were analyzed for both spinal and cortical level muscle response times: gastrocnemius (G), lateral hamstring (LH) , medial hamstring (MH) , lateral quadriceps (LQ) , and medial quadriceps (MQ). All tests were performed at time 0 and 6 weeks. A power analysis and a one-way ANOVA with repeated measures was used to determine differences between groups (p<O.OS). When compared to the control group, the agility training group decreased the gastrocnemius spinal reflex time by 41.9 ms. Although not significant, the agility group also reduced the spinal reflex time in the remaining four muscle groups; neither the isokinetic nor isotonic groups showed a significant reduction. Cortical response time of the agility group was significantly decreased in the medial hamstrings (93 .2 ms) and lateral hamstrings (92.0 ms). The cortical response time of the lateral hamstrings in the isokinetic group was also significantly reduced by 61.5 ms; the isotonic group showed no changes in muscle reaction time. All three muscle training groups helped reduce muscle reaction time to some extent. The agility training program was shown to be superior to the others. Functional agility exercises may have the potential to improve anterior tibial translation (ATT) which is an important parameter. Therefore, agility training may be more effective than isotonic or isokinetic training at improving muscle function.