Sex differences in the fatigability of arm muscles depends on absolute force during isometric contractions.

Women are capable of longer endurance times compared with men for contractions performed at low to moderate intensities. The purpose of the study was 1) to determine the relation between the absolute target force and endurance time for a submaximal isometric contraction and 2) to compare the pressor response and muscle activation patterns of men [26.3 +/- 1.1 (SE) yr] and women (27.5 +/- 2.3 yr) during a fatiguing contraction performed with the elbow flexor muscles. Maximal voluntary contraction (MVC) force was greater for men (393 +/- 23 vs. 177 +/- 7 N), which meant that the average target force (20% of MVC) was greater for men (79.7 +/- 6.5 vs. 36.7 +/- 2.0 N). The endurance time for the fatiguing contractions was 118% longer for women (1,806 +/- 239 vs. 829 +/- 94 s). The average of the rectified electromyogram (%MVC) for the elbow flexor muscles at exhaustion was similar for men (31 +/- 2%) and women (30 +/- 2%). In contrast, the heart rate and mean arterial pressure (MAP) were less at exhaustion for women (94 +/- 6 vs. 111 +/- 7 beats/min and 121 +/- 5 vs. 150 +/- 6 mmHg, respectively). The target force and change in MAP during the fatiguing contraction were exponentially related to endurance time (r(2) = 0.68 and r(2) = 0.64, respectively), whereas the change in MAP was linearly related to target force (r(2) = 0.51). The difference in fatigability of men and women when performing a submaximal contraction was related to the absolute contraction intensity and was limited by mechanisms that were distal to the activation of muscle.

[1]  S. Homma,et al.  Brachial arterial blood flow during static handgrip exercise of short duration at varying intensities studied by a Doppler ultrasound method. , 1997, Acta physiologica Scandinavica.

[2]  R D Herbert,et al.  A randomized trial of preexercise stretching for prevention of lower-limb injury. , 2000, Medicine and science in sports and exercise.

[3]  A. Ng,et al.  Age and gender influence muscle sympathetic nerve activity at rest in healthy humans. , 1993, Hypertension.

[4]  A. R. Lind,et al.  Comparison of physiological responses of women and men to isometric exercise. , 1975, Journal of applied physiology.

[5]  L. Sinoway,et al.  Influences of gender on sympathetic nerve responses to static exercise. , 1996, Journal of applied physiology.

[6]  A. Hicks,et al.  The effect of age and gender on the relative fatigability of the human adductor pollicis muscle. , 2000, Canadian journal of physiology and pharmacology.

[7]  H. Tamaki,et al.  Alternate activity in the synergistic muscles during prolonged low-level contractions. , 1998, Journal of applied physiology.

[8]  O. Sejersted,et al.  Intramuscular fluid pressure during isometric contraction of human skeletal muscle. , 1984, Journal of applied physiology: respiratory, environmental and exercise physiology.

[9]  D. Seals.  Influence of active muscle size on sympathetic nerve discharge during isometric contractions in humans. , 1993, Journal of applied physiology.

[10]  Martin Posch,et al.  Load-dependence of fatigue related changes in tremor around 10 Hz , 2000, Clinical Neurophysiology.

[11]  G. A. Robinson,et al.  Behavior of motor units in human biceps brachii during a submaximal fatiguing contraction. , 1994, Journal of applied physiology.

[12]  F. Nagle,et al.  Time to fatigue during isometric exercise using different muscle masses. , 1988, International journal of sports medicine.

[13]  O. Lippold,et al.  The 4‐6 HZ tremor during sustained contraction in normal human subjects. , 1983, The Journal of physiology.

[14]  J. Mitchell,et al.  The exercise pressor reflex: its cardiovascular effects, afferent mechanisms, and central pathways. , 1983, Annual review of physiology.

[15]  W. Rumsey,et al.  Effect of estradiol on tissue glycogen metabolism in exercised oophorectomized rats. , 1987, Journal of applied physiology.

[16]  Z. Kendrick,et al.  Effect of estradiol on tissue glycogen metabolism and lipid availability in exercised male rats. , 1991, Journal of applied physiology.

[17]  J. Mitchell,et al.  Effects of static muscular contraction on impulse activity of groups III and IV afferents in cats. , 1983, Journal of applied physiology: respiratory, environmental and exercise physiology.

[18]  M. Tarnopolsky.  Gender differences in substrate metabolism during endurance exercise. , 2000, Canadian journal of applied physiology = Revue canadienne de physiologie appliquee.

[19]  R. Enoka,et al.  Limb immobilization alters muscle activation patterns during a fatiguing isometric contraction , 2000, Muscle & nerve.

[20]  C. Williams.  Effect of muscle mass on the pressor response in man during isometric contractions. , 1991, The Journal of physiology.

[21]  T. Rooney,et al.  Effect of estradiol on the temporal pattern of exercise-induced tissue glycogen depletion in male rats. , 1993, Journal of applied physiology.

[22]  A Cymerman,et al.  Slower fatigue and faster recovery of the adductor pollicis muscle in women matched for strength with men. , 1999, Acta physiologica Scandinavica.

[23]  A J Fuglevand,et al.  Impairment of neuromuscular propagation during human fatiguing contractions at submaximal forces. , 1993, The Journal of physiology.

[24]  L. Rowell,et al.  Reflex control of the circulation during exercise: chemoreflexes and mechanoreflexes. , 1990, Journal of applied physiology.

[25]  B. Carlson.  Level of maxinum isometric strength and relative load isometric endurance. , 1969, Ergonomics.

[26]  J Ohashi,et al.  Sex differences in static muscular endurance. , 1989, Journal of human ergology.

[27]  J. Dowling,et al.  The relationship between voluntary electromyogram, endurance time and intensity of effort in isometric handgrip exercise , 1995, European Journal of Applied Physiology and Occupational Physiology.

[28]  R M Enoka,et al.  Gender differences in the fatigability of human skeletal muscle. , 1999, Journal of neurophysiology.

[29]  W. Barnes,et al.  The relationship between maximum isometric strength and intramuscular circulatory occlusion. , 1980, Ergonomics.

[30]  M. Tarnopolsky,et al.  Gender differences in substrate for endurance exercise. , 1990, Journal of applied physiology.

[31]  A. R. Lind,et al.  Local and central circulatory responses to sustained contractions and the effect of free or restricted arterial inflow on post‐exercise hyperaemia , 1967, The Journal of physiology.

[32]  M. Kaufman,et al.  Pressor reflex response to static muscular contraction: its afferent arm and possible neurotransmitters. , 1988, The American journal of cardiology.

[33]  A. Kunselman,et al.  Effects of the ovarian cycle on sympathetic neural outflow during static exercise. , 1998, Journal of applied physiology.

[34]  D. Seals.  Influence of force on muscle and skin sympathetic nerve activity during sustained isometric contractions in humans. , 1993, The Journal of physiology.

[35]  G. Sjøgaard,et al.  Cardiovascular and metabolic responses to static contraction in man. , 1990, Acta physiologica Scandinavica.

[36]  G Sjøgaard,et al.  Intramuscular pressure, EMG and blood flow during low-level prolonged static contraction in man. , 1986, Acta physiologica Scandinavica.

[37]  R. Enoka,et al.  Sympathetic activation is associated with increases in EMG during fatiguing exercise. , 1989, Journal of applied physiology.

[38]  L. Rowell.  Human Cardiovascular Control , 1993 .

[39]  F G Shellock,et al.  The effects of eccentric velocity on activation of elbow flexors: evaluation by magnetic resonance imaging. , 2001, Medicine and science in sports and exercise.

[40]  A. G. Cresswell,et al.  Significance of peripheral afferent input to the α-motoneurone pool for enhancement of tremor during an isometric fatiguing contraction , 2000, European Journal of Applied Physiology.