Fatigue and recovery at long and short muscle lengths following resistance training.
Med Sci Sports Exerc 2002 Nov; 34(11):1738-1743
To determine the effects of high-speed eccentric training of rat plantar flexor muscles on: 1) maximum (120 Hz) force at 90[degrees] ankle position; 2) fatigue (40 concentric muscle actions, ROM 50[degrees]) and recovery (6 concentric muscle actions) tested at short or long muscle lengths; and 3) low-frequency fatigue. Training consisted of eccentric muscle actions from ankle positions of 140[degrees] to 40[degrees] (velocity approximately 400 degrees [middle dot]s-1) followed by unresisted concentric muscle actions (5 x 10 repetitions, 5 d[middle dot]wk-1 for 6 wk). Fatigue was induced by concentric muscle actions with a rest of 12.5 s between muscle actions, and recovery consisted of equivalent concentric muscle actions performed every 5 min for 30 min. Low-frequency fatigue was measured 35 min after testing at 90[degrees] ankle position by using the ratio of isometric force produced by 20- and 100-Hz stimulation frequencies. Eccentric training increased maximal isometric force per muscle weight by 22% whereas muscle weights were unchanged. In control muscles (C), isometric force immediately preceding each concentric muscle action decreased more at long lengths than at short lengths during the fatigue protocol; this length-dependent difference disappeared after 30 min of recovery. At short lengths, isometric force decreased less in trained muscles (T) (C: 78.4 +/- 3.6%; T: 59.6 +/- 4.4%) and recovered more during the following 30-min period (C: 84.7 +/- 2.5%; T: 95.4 +/- 2.8% of initial values). Changes in F20/F100 were smaller for trained muscles (C: 35.4 +/- 2.0%; T: 22.0 +/- 1.4%). High-speed eccentric training (5 d[middle dot]wk-1 for 6 wk) reduced fatigability and enhanced recovery mainly at long muscle lengths. It also reduced low-frequency fatigue, which may be attributed to alterations in intracellular calcium handling.
Laboratory-animals; Animals; Animal-studies; Muscles; Musculoskeletal-system; Skeletal-system; Injuries; Muscle-tissue; Fatigue
Department of Biochemistry, P.O. Box 9142, West Virginia University Health Sciences Center, Morgantown, WV 26506-9142
Disease and Injury: Musculoskeletal Disorders of the Upper Extremities
Medicine and Science in Sports and Exercise
West Virginia University, Morgantown, West Virginia