Effects of isotonic (Dynamic constant external resistance) eccentric strength training at various speeds on concentric and isometric strength of quadriceps muscle

Study design Randomized controlled trial. Background and purpose The velocity of muscular contraction used to perform dynamic muscle actions affect the neural81,26,48, hypertrophic41 and metabolic49 responses to resistance exercise. The purpose of this study was to find out differential training effects of slow and fast eccentric strength training (no concentric contraction) on concentric and isometric strength of the quadriceps muscle. Subjects Physically active normal males and females (n=45) in the age group of 18-25 yrs with asymptomatic knee function were included. Methods The subjects were randomly assigned to three groups: Group A (fast eccentric training), Group B (slow eccentric training), Group C (control group with no training). Group A and B underwent eccentric training for a period of 4 weeks for 3days/week, whereas group C acted as a control group with no training. Results A change of 15.01%, 37.71 % and 1.38% was observed in lRM value for Group A, Group B and Group C respectively The isometric strength for Group A improved by 9.78%,8.35% and 8.52% at 15°,45° and 75° respectively and for Group B' improved by 22.7%, 24.58% and 24.16% at 15°, 45° and 75° respectively whereas insignificant changes occurred for Group C. The change in thigh circumference during the study period was found to be insignificant for all the three groups. Conclusion The eccentric training can be used as an effective stimulus to develop concentric and isometric strength for Quadriceps muscles in previously untrained individuals. The significant difference obtained between Group A and Group B indicates that eccentric strength training at slower velocities can produce greater amount of strength gains as compared to training at comfortable natural speed.