Neuromuscular fatigue after resistance training.

This study examined the effects of heavy resistance training on dynamic exercise-induced fatigue task (5 x 10RM leg-press) after two loading protocols with the same relative intensity (%) (5 x 10RM(Rel)) and the same absolute load (kg) (5 x 10RM(Abs)) as in pretraining in men (n=12). Maximal strength and muscle power, surface EMG changes [amplitude and spectral indices of muscle fatigue], and metabolic responses (i.e.blood lactate and ammonia concentrations) were measured before and after exercise. After training, when the relative intensity of the fatiguing dynamic protocol was kept the same, the magnitude of exercise-induced loss in maximal strength was greater than that observed before training. The peak power lost after 5 x 10RM(Rel) (58-62%, pre-post training) was greater than the corresponding exercise-induced decline observed in isometric strength (12-17%). Similar neural adjustments, but higher accumulated fatigue and metabolic demand were observed after 5 x 10RM(Rel). This study therefore supports the notion that similar changes are observable in the EMG signal pre- and post-training at fatigue when exercising with the same relative load. However, after training the muscle is relatively able to work more and accumulate more metabolites before task failure. This result may indicate that rate of fatigue development (i.e. power and MVC) was faster and more profound after training despite using the same relative intensity.

[1]  H J Green,et al.  Glycogen depletion patterns during ice hockey performance. , 1978, Medicine and science in sports.

[2]  William J. Kraemer,et al.  Muscle hypertrophy, hormonal adaptations and strength development during strength training in strength-trained and untrained men , 2003, European Journal of Applied Physiology.

[3]  R. Enoka,et al.  Muscle fatigue: what, why and how it influences muscle function , 2008, The Journal of physiology.

[4]  N. Dimitrova,et al.  Muscle fatigue during dynamic contractions assessed by new spectral indices. , 2006, Medicine and science in sports and exercise.

[5]  R. McKelvie,et al.  Muscle performance and enzymatic adaptations to sprint interval training. , 1998, Journal of applied physiology.

[6]  Paavo V. Komi,et al.  EMG frequency spectrum, muscle structure, and fatigue during dynamic contractions in man , 1979, European Journal of Applied Physiology and Occupational Physiology.

[7]  J. Henriksson,et al.  Buffer capacity and lactate accumulation in skeletal muscle of trained and untrained men. , 1984, Acta physiologica Scandinavica.

[8]  E. Simonsen,et al.  Increased rate of force development and neural drive of human skeletal muscle following resistance training. , 2002, Journal of applied physiology.

[9]  K. Hainaut,et al.  Isometric or dynamic training: differential effects on mechanical properties of a human muscle. , 1984, Journal of applied physiology: respiratory, environmental and exercise physiology.

[10]  A. Thorstensson,et al.  Enzyme activities and muscle strength after "sprint training" in man. , 1975, Acta physiologica Scandinavica.

[11]  B. Bigland-ritchie,et al.  Conduction velocity and EMG power spectrum changes in fatigue of sustained maximal efforts. , 1981, Journal of applied physiology: respiratory, environmental and exercise physiology.

[12]  M. Falduto,et al.  Successive time courses of strength development and steroid hormone responses to heavy-resistance training. , 1994, Journal of applied physiology.

[13]  A S Jackson,et al.  Generalized equations for predicting body density of men , 1978, British Journal of Nutrition.

[14]  P. Aagaard,et al.  Myosin heavy chain IIX overshoot in human skeletal muscle , 2000, Muscle & nerve.

[15]  P V Komi,et al.  Changes in isometric force- and relaxation-time, electromyographic and muscle fibre characteristics of human skeletal muscle during strength training and detraining. , 1985, Acta physiologica Scandinavica.

[16]  W J Kraemer,et al.  Skeletal muscle adaptations during early phase of heavy-resistance training in men and women. , 1994, Journal of applied physiology.

[17]  K. Häkkinen,et al.  The effects of short-term resistance training on endocrine function in men and women , 1998, European Journal of Applied Physiology and Occupational Physiology.

[18]  W J Kraemer,et al.  Acute and chronic hormonal responses to resistance training designed to promote muscle hypertrophy. , 1999, Canadian journal of applied physiology = Revue canadienne de physiologie appliquee.

[19]  J. Duchateau,et al.  Limiting mechanisms of force production after repetitive dynamic contractions in human triceps surae. , 2004, Journal of applied physiology.

[20]  L. Nybo,et al.  Effect of two different intense training regimens on skeletal muscle ion transport proteins and fatigue development. , 2007, American journal of physiology. Regulatory, integrative and comparative physiology.

[21]  P. V. Komi,et al.  Neuromuscular fatigue and recovery in maximal compared to explosive strength loading , 1997, European Journal of Applied Physiology and Occupational Physiology.

[22]  W. Stauber,et al.  Isotonic dynamometry for the assessment of power and fatigue in the knee extensor muscles of females. , 2000, Clinical physiology.

[23]  R. Fitts.  Cellular mechanisms of muscle fatigue. , 1994, Physiological reviews.

[24]  Y. Hellsten,et al.  Effect of sprint cycle training on activities of antioxidant enzymes in human skeletal muscle. , 1996, Journal of applied physiology.

[25]  B. Saltin,et al.  Oxygen deficit and muscle metabolites in intermittent exercise. , 1971, Acta physiologica Scandinavica.

[26]  P. Sacco,et al.  Loss of power during fatigue of human leg muscles. , 1995, The Journal of physiology.

[27]  E. Simonsen,et al.  A mechanism for increased contractile strength of human pennate muscle in response to strength training: changes in muscle architecture , 2001, The Journal of physiology.

[28]  Charles L Rice,et al.  Fatigue and recovery of power and isometric torque following isotonic knee extensions. , 2005, Journal of applied physiology.

[29]  P. Bonato.  From the guest editor - recent advancements in the analysis of dynamic EMG data , 2001, IEEE Engineering in Medicine and Biology Magazine.

[30]  Juan José González-Badillo,et al.  Differential effects of strength training leading to failure versus not to failure on hormonal responses, strength, and muscle power gains. , 2006, Journal of applied physiology.

[31]  W J Kraemer,et al.  Changes in agonist-antagonist EMG, muscle CSA, and force during strength training in middle-aged and older people. , 1998, Journal of applied physiology.

[32]  J. Potvin.  Effects of muscle kinematics on surface EMG amplitude and frequency during fatiguing dynamic contractions. , 1997, Journal of applied physiology.

[33]  Dario Farina,et al.  Interpretation of the Surface Electromyogram in Dynamic Contractions , 2006, Exercise and sport sciences reviews.

[34]  J. Mitchell,et al.  Epidural anaesthesia and cardiovascular responses to static exercise in man. , 1989, The Journal of physiology.

[35]  I. Ara,et al.  Effects of weight lifting training combined with plyometric exercises on physical fitness, body composition, and knee extension velocity during kicking in football. , 2008, Applied physiology, nutrition, and metabolism = Physiologie appliquee, nutrition et metabolisme.