Effect of isotonic and isometric knee extension exercises on mechanical and electromyographical specificity of fatigue

Abstract: This study investigated the effects of isotonic and isometric knee extension exercises on strength, power, and surface EMG in male and female populations. Using the knee extensors, ten males and ten females performed a 120 s MVIC and 120 maximal isotonic contractions. Prior to each exercise (t = pre) knee extensor isometric peak torque (strength) and average peak power (power) were tested utilizing three, 3 s MVIC’s and three maximal isotonic contractions, respectively. Following each exercise, strength and power were assessed immediately after (t =: 00) and at 2.5 (t =: 02.5), 5 (t =: 05), 10 (t =: 10), and 15 (t =: 15) minutes. All strength and power measures were normalized to the respective t = pre value. Vastus lateralis surface EMG signals were collected during all muscle testing and normalized to the respective tire value. Following isometric exercise, both strength and power at t =: 00 (68.7% ± 8.7% & 88.0% ± 8.7%) and t =: 02.5 (82.2% ± 17.8% & 95.2% ± 5.0%) significantly decreased from t=pre (100% ± 0.0%) (p < 0.05) with greater decreases in strength at each time point (p < 0.05). EMG analysis revealed a significant EMG amplitude decrease (p < 0.05) at t =: 00 and t =: 02.5 during strength testing with respect to t=pre. Following isotonic exercise, both strength and power at t =: 00 (68.0% ± 13.2% & 38.8% ± 10.7%) and t =: 02.5 (84.5% ± 14.9% & 81.6% ± 14.5%) significantly decreased from t=pre (100% ± 0.0%) with a greater power decrease at t =: 00 (p < 0.05). The EMG amplitude of males was significantly less at t =: 00 than the respective EMG amplitude for females (p < 0.05) (irrespective of testing condition). We conclude that muscle performance in the fatigued state is dependent upon the type of exercise performed.

[1]  Toshio Moritani,et al.  Electromyographic evidence of selective fatigue during the eccentric phase of stretch/shortening cycles in man , 2004, European Journal of Applied Physiology and Occupational Physiology.

[2]  R U Newton,et al.  The optimal training load for the development of dynamic athletic performance. , 1993, Medicine and science in sports and exercise.

[3]  J. Hannerz,et al.  Firing rate and recruitment order of toe extensor motor units in different modes of voluntary conraction. , 1977, The Journal of physiology.

[4]  Lars Arendt-Nielsen,et al.  Muscle fibre conduction velocity, mean power frequency, mean EMG voltage and force during submaximal fatiguing contractions of human quadriceps , 2004, European Journal of Applied Physiology and Occupational Physiology.

[5]  Petrofsky Js.  Quantification through the surface EMG of muscle fatigue and recovery during successive isometric contractions. , 1981 .

[6]  H. Milner-Brown,et al.  Quantifying human muscle strength, endurance and fatigue. , 1986, Archives of physical medicine and rehabilitation.

[7]  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.

[8]  M W Weiner,et al.  Effects of fatiguing exercise on high‐energy phosphates, force, and EMG: Evidence for three phases of recovery , 1987, Muscle & nerve.

[9]  J. Bangsbo,et al.  Moment and power generation during maximal knee extensions performed at low and high speeds , 2004, European Journal of Applied Physiology and Occupational Physiology.

[10]  Stull Ga,et al.  Patterns of recovery following isometric and isotonic strength decrement , 1971 .

[11]  J. Richards,et al.  Validity and reliability of the BTE dynatrac. , 1996, Medicine and science in sports and exercise.

[12]  K. Granata,et al.  Changes in the mechanical and electromyographic output during isotonic and isometric exercise in men and women , 2000 .

[13]  T. Fukunaga,et al.  Sex difference in force generation capacity during repeated maximal knee extensions , 2004, European Journal of Applied Physiology and Occupational Physiology.

[14]  J. Stephens,et al.  Fatigue of maintained voluntary muscle contraction in man , 1972, The Journal of physiology.

[15]  L. Arendt-Nielsen,et al.  The relationship between mean power frequency of the EMG spectrum and muscle fibre conduction velocity. , 1985, Electroencephalography and clinical neurophysiology.

[16]  C. Bouchard,et al.  Human variation in skeletal muscle fiber-type proportion and enzyme activities. , 1989, The American journal of physiology.

[17]  J T Viitasalo,et al.  Influence of lactate accumulation of EMG frequency spectrum during repeated concentric contractions. , 1983, Acta physiologica Scandinavica.

[18]  D. Newham,et al.  Changes in force and intracellular metabolites during fatigue of human skeletal muscle. , 1989, The Journal of physiology.

[19]  R. Josephson.  Contraction dynamics and power output of skeletal muscle. , 1993, Annual review of physiology.

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

[21]  Marcas M. Bamman,et al.  Evaluation of Surface Electromyography During Maximal Voluntary Contraction , 1997 .

[22]  A. de Haan,et al.  Changes in velocity of shortening, power output and relaxation rate during fatigue of rat medial gastrocnemius muscle , 1989, Pflügers Archiv.

[23]  R. H. T. Edwards,et al.  The time course of phosphorylcreatine resynthesis during recovery of the quadriceps muscle in man , 1976, Pflügers Archiv.

[24]  B Jonsson,et al.  Mean power frequency and integrated electromyogram of repeated isokinetic plantar flexions. , 1987, Acta physiologica Scandinavica.

[25]  B Bigland-Ritchie,et al.  Central and peripheral fatigue in sustained maximum voluntary contractions of human quadriceps muscle. , 1978, Clinical science and molecular medicine.

[26]  R. Johansson,et al.  Contractile speed and EMG changes during fatigue of sustained maximal voluntary contractions. , 1983, Journal of neurophysiology.

[27]  A Thorstensson,et al.  Fatigue and EMG of repeated fast voluntary contractions in man. , 1977, Acta physiologica Scandinavica.