摘要:

NOAKES, T. D. Implications of exercise testing for prediction of athletic performance: a contemporary perspective. Meet. Sci. Sports Exerc, Vol. 20, No. 4, pp. 319-330, 1988. One of the most fundamental beliefs in exercise physiology is that performance during maximum exercise of short duration is limited by the inability of the heart and lungs to provide oxygen at a rate sufficiently fast to fuel energy production by the active muscle mass. This belief originates from work undertaken in the 1920's by Hill and Lupton. A result is that most, if not all, of the studies explaining the effects of exercise training or detraining or other interventions on human physiology explain these changes in terms either of central adaptations increasing oxygen delivery to muscle or of peripheral adaptations that modify. the rates of oxygen or fuel utilization by the active muscles. Yet a critical review of Hill and Lupton's results shows that they inferred but certainly did not prove that oxygen limitation develops during maximal exercise. Furthermore, more modern studies suggest that, if such an oxygen limitation does indeed occur during maximal exercise, it develops in about 50% of test subjects. Thus, an alternative mechanism may need to be evoked to explain exhaustion' during maximal exercise in a rather large group of subjects. This review proposes that the factors limiting maximal exercise performance might be better explained in terms of a failure of muscle contractility (“muscle power”), which may be independent of tissue oxygen deficiency. The implications for exercise testing and the prediction of athletic performance are discussed.

ISSN:0195-9131    

出版商:OVID    

年代:1988

数据来源: OVID

摘要:

WEBB, P., W. H. M. SARIS, P. F. M. SCHOFFELEN, G. J. VANINGEN SCHENAU, and F. TEN HOOR. The work of walking: a calorimetric study. Med, Sci. Sports Exerc, Vol. 20, No. 4, pp. 331- 337, 1988. Experiments were designed to test the traditional assumption that during level walking all of the energy from oxidation of fuel appears as heat and no work is done. Work is force expressed through distance, or energy transferred from a man to the environment, but not as heat. While wearing a suit calorimeter in a respiration chamber, five women and five men walked for 70 to 90 min on a level treadmill at 2.5, 4.6, and 6.7 km·h−1and pedaled a cycle ergometer for 70 to 90 min against 53 and 92 W loads. They also walked with a weighted backpack and against a horizontal load. During cycling, energy from fuel matched heat loss plus the power measured by the ergometer. During walking, however, energy from fuel exceeded that which appeared as heat, meaning that work was done. The power increased with walking speed; values were 14, 29, and 63 W, which represented 11, 12, and 13% of the incremental cost of fuel above the resting level. Vertical and horizontal loads increased the fuel cost and heat loss of walking but did not alter the power output. This work energy did not re-appear as thermal energy during 18 h of recovery. The most likely explanation of the work done is in the inter-action between the foot and the ground, such as compressing the heel of the shoe and bending the sole. We conclude that work is done in level walking.

ISSN:0195-9131    

出版商:OVID    

年代:1988

数据来源: OVID

摘要:

CURETON, K. J., M. A. COLLINS, D. W. HILL, and F. M. MCELHANNON, JR. Muscle hypertrophy in men and women. Med. Sci. Sports. Exerc, Vol. 20, No. 4, pp. 338-344, 1988. It is widely believed that women experience less skeletal muscle hypertrophy consequent to heavy-resistance training than men. The purpose of this study was to test this hypothesis using both traditional indirect indicators as well as a direct measure of muscle size. Seven male experimental (ME), 8 female experimental (FE), and 7 control subjects were studied before and after a 16-wk weight training program, in which ME and FE trained 3 days·wk−1at 70 to 90% of maximum voluntary contraction using exercise designed to produce hypertrophy of the upper arm and thigh. Strength increased significantly (P<0.05) in ME and FE, respectively, on elbow flexion (36.2 and 59.2%), elbow extension (32.6 and 41.7%), knee flexion (12.8 and 24.4%), and knee extension (28.8 and 33.9%) tests. Absolute changes were significantly greater in ME than FE in 2 of the 4 tests, whereas percentage changes were not significantly different. Substantial muscle hypertrophy occurred in the upper arms of both ME and FE as evidenced by significant increases in upper arm circumference (7.9 and 7.9%), bone-plus-muscle (B+M) cross-sectional area (CSA) estimated by anthropometry (17.5 and 20.4%), and muscle CSA determined from computed tomography scanning (15.9 and 22.8%). Changes by ME and FE were not significantly different, except for the absolute increase in estimated B+M CSA, which was significantly greater in ME (11.2 vs 7.4 cm2). No muscle hypertrophy occurred in the thigh of either ME and FE as evidenced by non-significant changes in thigh circumference (1.7 and 2.3%), B+M CSA (4.9 and 6.1%), and muscle CSA (2.9 and 2.9%). Changes by ME and FE in body weight, fat-free weight, and fat weight were not significant. We conclude that relative changes in strength and muscle hypertrophy consequent to weight training are similar in men and women.

ISSN:0195-9131    

出版商:OVID    

年代:1988

数据来源: OVID

摘要:

STAUBER, W.T., V.K. FRITZ, D.W. VOGELBACH, and B. DAHLMANN. Characterization of muscles injured by forced lengthening. Med. Sci. Sports Exerc, Vol. 20, No. 4, pp. 345-353, 1988. Myofiber injury-repair was studied in rat soleus muscles to elucidate the role of infiltrating cells in the injury-repair process. Muscle injury was induced by forced muscle lengthening with the contralateral muscle serving as a control. The muscles were removed for histologic, histochemical and immunohistochemical procedures at varying periods (12-120 h) post-injury. All injured muscles were severely damaged with many cells present in the interstitial spaces between myofibers. Normal appearing myofibers demonstrated elevated lysosomal proteolytic activity, but no evidence of increased activity, indicative of phagocytic cells, was found in or between damaged myofibers. The esterase stain for macrophages and immunohistochemical techniques for mast cells also provided no support for either cell type predominating in the damaged area, although mast cell degranulation could be observed in the pericapillary regions. In contrast, the use of a specific antisera for a multicatalytic protease uniquely defined most of these cells as myogenic in origin. They appeared to be most numerous between the torn ends of a myofiber. Surprisingly, the remainder of the cells appeared to be of lymphoid origin.

ISSN:0195-9131    

出版商:OVID    

年代:1988

数据来源: OVID

摘要:

FRITZ, V. K. and W. T. STAUBER. Characterization of muscles injured by forced lengthening. II. Proteoglycans. Med, Sci. Sports Exerc, Vol. 20, No. 4, pp. 354-361, 1988. After forced muscle lengthening of rat soleus muscle, alterations in muscle connective tissues were monitored by fluorescent immunohistochemical methods. Monoclonal antibodies directed against the polysaccharide attachment region of proteoglycans were used to observe changes in localization of 4-sulfated, 6-sulfated, or unsulfated chondroitin sulfate disaccharide units covalently bound to the proteoglycan protein core after injury. Additionally, fluorescein-labeled concanavalin A lectin and polyclonal antiserum to heparan sulfate proteoglycan were also localized in muscle sections during the regenerative process over 5 days after injury. Although proteoglycan localization was absent at or near the site of myofiber damage after injury, some distinct basal lamina remained as a matrix for regenerating myofibers. By the fifth day post-injury, the localization of these matrix components had returned to that seen in uninjured soleus muscles. The physiological significance of these extracellular matrix changes appeared to center on the repair of the torn myofiber and indicate an interdependence between myofibers and the extracellular matrix in this type of regeneration.

ISSN:0195-9131    

出版商:OVID    

年代:1988

数据来源: OVID

摘要:

MCCARTNEY, N., D. MOROZ, S. H. GARNER, and A. J. MCCOMAS. The effects of strength training in patients with selected neuromuscular disorders. Meet. Sci. Sports Exerc, Vol. 20, No. 4, pp. 362-368, 1988. Five subjects with spinal muscular atrophy, limb-girdle or facioscapulohumeral muscular dystrophy, were studied. Measurements pre- and post-training included: maximum isometric, dynamic and isokinetic strength, in single-arm curl and double-leg press exercises; contractile properties of the elbow flexors; computerized tomography of the upper arms and thighs; muscle biopsies from the biceps brachii muscle of each arm in three subjects. Dynamic weight training was performed 3 times per week for 9 wk; exercises comprised unilateral arm curls (the contralateral arm acted as a control), and bilateral leg press. Strength increases in the trained arm were between 19 and 34%, and from -14 to +25% in the control arm; leg strength increased from 11 to 50%. Moreover, the pre-training maximum load could be lifted from 3 to 48 times in the trained limbs, and from 1 to 13 times in an untrained limb before fatigue. Contractile properties of the elbow flexors were unchanged with training, but pre-intervention, three subjects demonstrated incomplete motor unit activation. Most of the gains in strength were apparently due to a neural adaptation, rather than muscle hypertrophy. The tomograms and biopsy samples were inadequate to determine muscle, or muscle fiber areas with confidence; they did indicate however, no additional overt muscle structural damage. Strength training may be a potentially useful therapeutic option in the management of selected neuromuscular disorders.

ISSN:0195-9131    

出版商:OVID    

年代:1988

数据来源: OVID

摘要:

STAGER, J. M. AND L. K. HATLER. Menarche in athletes: the influence of genetics and prepubertal training. Med. Sci. Sports Exerc, Vol. 20, No. 4, pp. 369-373, 1988. It is unclear whether the later menarche observed in competitive athletes is due to genetic factors or environmental factors related to intense prepubertal training. In order to investigate the importance of these factors upon the age of menarche (AOM), 263 competitive swimmers and 71 women with no athletic experience were asked to complete questionnaires concerning general health and reproductive development. Based upon their responses, similar questionnaires were sent to the sisters of both groups. Complete data were obtained from 140 athlete/sister pairs and 43 control/sister pairs. Results indicate that the athletes were older at menarche than their sisters, the non-athletes, and the sisters of the non-athletes (14.3 yr, 13.7yr, 12.9 yr, and 13.0 yr, respectively). The sisters of the athletes were significantly older at menarche than the controls and their sisters, while the AOM of the non-athletic controls and their sisters did not differ. The interpretation of the data is complicated by the fact that the sisters of the athletes were likely to be athletes (75%), while those of the control group tended to be non-athletic (74%). The athletes differed from their sisters who trained prior to menarche (13.9 years) and from those who did not engage in prepubertal training (13.1 years). Controls did not differ from any of their sister groups, nor did they differ from the untrained sisters of athletes. In terms of the similarity of the AOM within the sister pairs, the athletes/sisters and controls/sisters were equally similar. Significant correlations were observed between athletes and their sisters who trained prior to menarche and controls and their sisters who did not. The data can be interpreted to support the importance of inherited characteristics and intense prepubertal activity upon the AOM of athletes. Because neither factor can absolutely be ruled out, it is proposed that both factors may be involved in the observed later menarche of competitive swimmers. However, a similar conclusion cannot be drawn from athletic populations who do not begin athletic participation until menarche has already been attained. This suggests that the later menarche is a function of factors associated with enhanced or prolonged athletic performance.

ISSN:0195-9131    

出版商:OVID    

年代:1988

数据来源: OVID

摘要:

SYMONS, J. D., T. VANHELDER, and W. S. MYLES. Physical performance and physiological responses following 60 hours of sleep deprivation. Med. Sci. Sports Exerc, Vol. 20, No. 4, pp. 374-380, 1988. The effect of 60 h of sleep deprivation (SD) upon physical performance and physiological responses to exercise was examined in 11 male subjects. The experiment consisted of two conditions separated by at least 10 d. In the experimental condition (E) subjects remained awake for 60 h and in the control condition (C) the same subjects had 7 h of sleep per night. In both conditions subjects reported to the laboratory on the evening prior to d 1 and slept for 7 h. Physical performance testing was carried out on d 1 and again on d 3 after either two nights of sleep or two nights of SD. Results obtained on d 3 are expressed relative to d 1, the control day. Maximal isometric and isokinetic muscular strength and endurance of selected upper and lower body muscle groups, performance of the Wingate Anaerobic Power Test, simple reaction time, the blood lactate response to cycle exercise at 70% &OV0312;O2max, and most of the cardiovascular and respiratory responses to treadmill running at 70% and 80% &OV0312;O2max, were not significantly altered as a result of SD. These results suggest that sleep loss of up to 60 h will not impair the capability for physical work, a finding of considerable importance in sustained military operations which frequently involve the combination of both physical and mental tasks.

ISSN:0195-9131    

出版商:OVID    

年代:1988

数据来源: OVID

摘要:

SCHWELLNUS, M. P. and N. F. GORDON. Effect of opioid antagonism on esophageal temperature during exercise. Med. Sci. Sports Exerc, Vol. 20, No. 4, pp. 381-384, 1988. The effect of naloxone-induced endogenous opioid antagonism on core temperature control during exercise was studied in 8 competitive cyclists. Volume-matched infusions of placebo or 2 mg of naloxone were administered, in a randomized double-blind crossover fashion, prior to maximal graded cycle ergometer exercise testing. Esophageal (Tes), rectal (Tre) and oral (Tor) temperatures were measured before and after exercise, and Tes was continuously measured during exercise. Cardiorespiratory responses and maximal exercise duration were unaffected by naloxone. Naloxone did not significantly modify the Tes response or the highest Tre and Tor elicited by exercise testing. The rise in Tes (placebo: 2.2 ± 0.4°C; naloxone: 2.1 ± 0.4°C) and Tre (placebo: 1.1 ± 0.2°C; naloxone: 0.9 ± 0.4°C) was significant (p<0.001) with and without naloxone, whereas the rise in Tor was significant (p<0.05) with placebo (0.5 ± 0.5°C) but not with naloxone (0 ± 0.8°C, p>0.5). These data indicate that although 2 mg of naloxone might alter heat exchange in the oral cavity during exercise, it does not modify the actual core temperature response. Therefore, insofar as this dosage of naloxone may be used to examine the functional role of opioid-mediated mechanisms, our findings are not tenable with the hypothesis that endogenous opioids play a role in maintenance of thermal homeostasis during exercise.

ISSN:0195-9131    

出版商:OVID    

年代:1988

数据来源: OVID

摘要:

KREIDER, R. B., T. BOONE, W. R. THOMPSON, S. BURKES, and C. W. CORTES. Cardiovascular and thermal responses of triathlon performance. Med. Sci. Sports Exerc, Vol. 20, No. 4, pp. 385- 390, 1988. Triathletes typically train each triathlon event separately. Therefore, to determine the cardiovascular and thermal differences between training and triathlon performance, nine male triathletes performed a simulated 75-min (40 km) control bike and a 40-min (10 km) control run at 70% of maximal oxygen uptake. Control data were compared to data derived from a simulated triathlon (0.8-km swim, 75-min bike, and 40-min run). Results demonstrated that prior swimming significantly decreased (P<0.05) triathlon cycling work output (191 ± 4.2 to 159 ± 7.6 W) producing mean differences (P<0.05) in oxygen uptake (3.18 ± 0.1 to 3.01 ± 0.1 l·min−1), ventilation (84.7 ± 4 to 80.4 ± 4.2 l·min−1). stroke volume (128 ± 7.1 to 118 ± 3.5 ml·min−1), cardiac output (20.7 ± 1.2 to 18.9 ± 0.8 l·min−1), mean arterial pressure (105 ± 3.8 to 96 ± 7.9 mm Hg) and rectal temperature (38.2 ± 0.2 to 38.4 ± 0.3°C). Triathlon running, while performing identical control work output, elicited significant increases (P<0.05) in oxygen uptake (3.41 ± 0.1 to 3.85 ±0.1 l·min−1), ventilation (91.3 ± 3.3 to 104.2 ± 2.8 l·min−1), heart rate (161 ±3.1 to 174 ± 3.6 beats·min−1),arteriovenous oxygen difference (15.3 ± 0.2 to 17.2 ± 0.3 ml-100 ml−1) and rectal temperature (38.3 ± 0.2 and 39.2 ± 0.3°C) with significantly lower (P<0.05) stroke volume (138 ± 2.4 to 129 ± 3.6 ml·min−1) and mean arterial pressure (102 ± 11.2 to 89 ± 5.5 mm Hg). Results demonstrate that triathlon performance elicited cardiovascular and thermal adjustments not experienced when performing the events independently. Findings appear to be a result of thermoregulatory and cardiovascular adaptations combined with a decrease in mechanical efficiency observed during prolonged triathlon performance.

ISSN:0195-9131    

出版商:OVID    

年代:1988

数据来源: OVID