Purpose: The effects of chronic eccentric-only versus concentric-only exercise on muscle physiology and blood biochemistry were investigated.
Methods: Twenty women performed on an isokinetic dynamometer a concentric (n = 10; mean ± SEM: age = 21.0 ± 0.4 yr, body fat = 22.0% ± 0.9%) or an eccentric (n = 10, age = 20.0 ± 0.3 yr, body fat = 23.2% ± 0.7%) exercise session using the knee extensors of both lower limbs once a week for eight subsequent weeks. Muscle function (isometric, concentric, and eccentric peak torque, range of movement, and soreness) was evaluated before, immediately after, and 48 h postexercise in each one of the eight training weeks. Body fat, resting energy expenditure (REE), lipid, and carbohydrate oxidation rate as well as blood chemistry measurements (lipid, lipoprotein and apolipoprotein profile, glucose, insulin, glycosylated hemoglobin, and creatine kinase) were examined before and 48 h postexercise at the first and eighth week of training.
Results: Acute eccentric exercise increased REE and fat oxidation at week 1 (12.7% and 12.9%, respectively) and at week 8 (0.7% and 2.8%, respectively). Chronic eccentric exercise increased resting REE and fat oxidation at week 8 compared with week 1 (5.0% and 9.9%, respectively). Acute eccentric exercise improved blood lipid profile at week 1 and week 8. Chronic eccentric exercise improved resting blood lipid profile at week 8. Acute eccentric exercise increased insulin resistance at week 1 but not at week 8. Chronic eccentric exercise decreased resting insulin resistance at week 8.
Conclusion: It is reported for the first time that only 30 min of eccentric exercise per week for 8 wk was sufficient to improve health risk factors.
1Institute of Human Performance and Rehabilitation, Center for Research and Technology-Thessaly, Trikala, GREECE; 2Department of Physical Education and Sport Science, University of Thessaly, Trikala, GREECE; 3Laboratory of Exercise, Health and Human Performance, Research Center, European University of Cyprus, Nicosia, CYPRUS; 4Department of Physical Education and Sport Science, University of Thrace, Komotini, GREECE; and 5School of Sport, Performing Arts and Leisure, Wolverhampton University, Walshall, UNITED KINGDOM
Submitted for publication December 2009.
Accepted for publication May 2010.
Address for correspondence: Michalis G. Nikolaidis, Ph.D., Institute of Human Performance and Rehabilitation, Center for Research and Technology-Thessaly, Karyes, 42100, Trikala, Greece; E-mail: firstname.lastname@example.org; email@example.com.