摘要:

The Guidelines for Exercise Training initially developed by the American College of Sports Medicine in 1978 and updated in 1990 have served as the foundation for most recommendations regarding physical activity program design for the general public. These guidelines have proven to be very useful by providing a specific regimen for enhancing aerobic capacity and body composition. As data supporting a causal link between increased activity or fitness and health status have evolved, questions have been raised about potential limitations of these guidelines for promoting physical activity to increase the health status of sedentary adults. The major issues have involved the necessity to achieve the values for each of the program parameters, especially the intensity, duration, and frequency of exercise, in order to improve health status. To address these issues, a paradigm shift from exercisetraining to promote physical fitness to physical activity to promote healthhas been introduced. This new paradigm is based on the results from numerous studies indicating that a generally active life style is associated with better health and performance and greater longevity and a certain set of assumptions, yet to be fully tested. The following article provides some background leading to the development of the ACSM guidelines and presents some of those issues we understand and some we do not regarding the characteristics of daily physical activity or exercise training that are likely to improve the physical health status of sedentary persons.

ISSN:0195-9131    

出版商:OVID    

年代:1994

数据来源: OVID

摘要:

Forty-three men (age 33 ± 9 yr) with spinal cord injuries (SCI) were observed during a normal workday while heart rate was recorded continuously. Physical strain was estimated using the heart rate response expressed relative to the individual heart rate reserve (%HRR). The mean physical strain during the day for group 1 (C4-C8,N= 9), II (T1-T5,N= 6), III (T6-T10,N= 15), and IV (T10-L5,N60%HRR) that might maintain or improve physical capacity were not identified during activities of daily life (ADL), but only during sports activities. The analysis of activity-related strain revealed that specific ADL such as making transfers, entering/leaving car, and negotiating environmental barriers, provoked high levels of strain, especially in those with quadriplegia. Periods of peak strain (>60%HRR,

ISSN:0195-9131    

出版商:OVID    

年代:1994

数据来源: OVID

摘要:

To determine whether exercise intensity influences acute HDL-C responses, 12 male recreational runners (24.8 ± 4 yr) who ran 15–30 miles wk−1exercised on a motor driven treadmill at 60% (L) and 75% (H) VO2max‘A counterbalanced experimental design was utilized and energy expenditure was 800 Keal. Fasting blood samples were obtained 24 h before exercise (24 PRE), immediately post- (IPE), 1 h post- (1 h PE), 6 h post- (6 h PE), and 24 h post- (24 h PE) exercise and analyzed for HDL-C and HDL2&3-C, In addition, postheparin plasma samples, obtained 24 h PRE, 6 h PE, and 24 h PE were analyzed for lipolytic activity—LPLA and HTGLA. An exercise trial by time interaction was observed for HDL-C (P< 0.01).Post-hocanalysis revealed no change in HDL-C following the L trial. However, an increase in HDL-C was observed 24 h PE (P< 0.01) following the H trial. The increase in HDL-C was attributed to an elevated HDL3-C (P< 0.01), with no change in HDL2-C. Analysis of plasma lipolytic activity revealed an increase in LPLA 24 h PE (P< 0.05) which may be responsible for the postexercise alterations in HDL-C. However, HTGLA decreased 6 h PE (P< 0.01) and 24 h PE (P< 0.05). We conclude that increases in HDL-C levels following endurance activity are influenced, in part, by the exercise intensity.

ISSN:0195-9131    

出版商:OVID    

年代:1994

数据来源: OVID

摘要:

We present a 53-yr-old man with congestive heart failure who underwent 32 wk of exercise training. The patient was on a continuous infusion of dobutamine for 10 months prior to exercise training, which was subsequently discontinued at wk 24 of exercise training. Symptom-limited graded exercise tests were performed at baseline, wk 12, wk 24, and wk 32 of exercise training. While on a continuous infusion of dobutamine, the patient's oxygen consumption and exercise duration were increased during the exercise training period. Additionally, the patient was able to maintain these changes for 8 wk while continuing to exercise after the discontinuation of the dobutamine therapy.

ISSN:0195-9131    

出版商:OVID    

年代:1994

数据来源: OVID

摘要:

This study examined current and proposed drug testing policies from a stratified random sample of colleges and universities in the United States. Two-hundred forty-five of the 288 athletic directors surveyed responded, and 29% reported drug testing of their student athletes. Testing was most commonly conducted on a random basis, with cocaine and amphetamines the most frequently screened drugs, 85% and 83%, respectively. Only 56% tested for other specific performance-enhancing drugs such as steroids. Referral for treatment was the most common consequence of testing positive. Among schools conducting testing, the majority of students supported the program, whereas in schools without a testing program, it was anticipated that the majority of students would be opposed. It is suspected that more schools will initiate testing over the short term.

ISSN:0195-9131    

出版商:OVID    

年代:1994

数据来源: OVID

摘要:

To determine whether heat stress sensitizes rats to lipopolysaccharide (LPS), four groups were examined: saline, LPS, heat stressed + saline, and heat stressed + LPS treated rats. Saline or LPS (Escherichia coli,5 mg'kg−1body weight, i.v.) was given after exposure to heat and at the same time of day for nonheated rats. Survival was monitored for 24 or 48 h; samples of liver and small intestine were obtained at 24 h for histological analysis. Thermal responses were similar (P> 0.05) for the heat stressed saline and LPS treated rats: mean values for maximum colon temperature were 43.0 ± 0.1 and 42.9 ± 0.1°C, respectively. Mortality was similar for rats exposed to heat stress + saline (11%, 2/19) and heat stress + LPS (32%, 6/19). No lethality was observed in nonheated rats given saline or LPS. Tissue damage was similar in heat stress + saline and heat stress + LPS treated rats. Liver showed mild to severe degrees of coagulative necrosis while duodenum exhibited damage to the villous tips. These findings show that severe heat stress does not markedly sensitize the rat to the lethal activity of LPS.

ISSN:0195-9131    

出版商:OVID    

年代:1994

数据来源: OVID

摘要:

Because cocaine causes a rapid sympathetic response and central euphoria, we tested whether it would improve endurance or alter carbohydrate metabolism during high-intensity activity. Thirty male rats (10 animals/group) were injected intraperitoneally with either saline (S) or one of two doses of cocaine-HCI (12.5 (C-I) or 20.0 (C-2) mg'kg−1b.w.), Ten minutes later they began gradually running on a rodent treadmill. Within 2 min they were running at 56 m.min−1until fatigued. The run time to exhaustion (mean ± SE) for C-2 (569 ± 97 s) was less than S (859 ± 71) and C-1 (923 ± 65) (P< 0.05) and 25% shorter (marginally insignificant) than a pretreatment run (754 ± 67 s) (P> 0.05). Plasma lactate concentrations at exhaustion were 4.0 ± 0.5 (S), 7.3 ± 1.1 (C-1), and 13.9 ± 2.5 (C-2) mmol (P< 0.05, S vs C-2). Lactate concentrations in white vastus muscle were also elevated by C (4.7 ± 0.6 (S), 8.1 ± 1.3 (C-1), and 15.0 ± 3.7 (C-2) μ mol.g−1, (P< 0.05, S vs C-2)], which correlated with the reduction in glycogen content in both C groups (9.9 ± 2.3 (C-2), 10.3 ± 1.2 (C-1), vs 33.9 ± 2.0 (S) μ mol.g−1]. These results show that, in spite of its purported stimulatory effect, cocaine treatment (20 mg.kg−1) immediately prior to intense exercise causes accelerated glycogen degradation and lactate accumulation in white vastus muscle during exercise and premature fatigue.

ISSN:0195-9131    

出版商:OVID    

年代:1994

数据来源: OVID

摘要:

Cardiovascular responses were obtained during cycling with graded levels of lower-body positive pressure (LBPP) applied to the exercising limbs. Seven men performed four incremental work rate (25 W.min−1) exercise (IWREx) tests to their limit of tolerance while exposed to 0, 15, 30, or 45 Torr LBPP. They also performed four, 6-min constant work rate exercise (CWREx) bouts at two work rates with LBPP's of 0 and 45 Torr. Cardiovascular data were obtained at rest and at 40%, 55%, 75%, and 90% of VO2peak‘ as well as at minute 5 of CWREx. LBPP did not alter VO2’HR, SV, or cardiac output (QC) responses at rest or during exercise. However, both 30 and 45 Torr LBPP produced increases in MAP at rest and during exercise (P< 0.05). During CWREx, elevations in blood pressure were mediated via increases in TPR (P< 0.05). Only 45 Torr LBPP elicited a significantly greater blood pressure increase during exercise than rest, suggesting muscle blood flow restriction at this level of LBPP was sufficient to activate a muscle metabo-reflex. These findings suggest that the muscle metabo-reflex is not tonically active during dynamic exercise under normal conditions, but may instead require a critical reduction in muscle blood flow before it is activated.

ISSN:0195-9131    

出版商:OVID    

年代:1994

数据来源: OVID

摘要:

Ten healthy subjects were evaluated at rest and at 5 min of unloaded active (AC) and passive (PC) cycling. Passive limb movements were accomplished using a tandem bicycle with a second rider performing the movements. We measured heart rate (HR), mean arterial pressure (MAP), cardiac output (CO), oxygen uptake (VO2), rating of perceived exertion (RPE), and electrical activity (EMG) of lower limbs muscles. Values for stroke volume (SV) and peripheral vascular resistance (PVR) were calculated. EMG, RPE, and VO2were higher during AC than during PC (P< 0.001). CO increased during both modes of cycling, but during AC it resulted from a HR acceleration (73 ± 2 at rest to 82 ± 2 beats.min−1at 60 rpm;P< 0.001) with no change in SV whereas during PC, SV increased from rest (65 ± 4 at rest to 71 ± 3 ml at 60 rpm;P= 0.003) along with no change in HR. PVR remained constant during PC, but decreased by 13% during AC (P< 0.001) and MAP increased only during PC (93 ± 2 at rest to 107 ± 2 mm Hg at 60 rpm). These results supports the concept that central command determines the HR response to dynamic exercise. The increase in SV and consequently in MAP during PC was probably due to increased venous return and/or to muscle mechano-receptor-evoked increased myocardial contractility.

ISSN:0195-9131    

出版商:OVID    

年代:1994

数据来源: OVID

摘要:

Ten male oarsmen performed a 6-min bout of “all-out” exercise on a rowing ergometer in the laboratory, Intraarterial blood pressure was recorded from a catheter inserted percutaneously into the radial artery. Mean arterial pressure increased only modestly from 110 ± 13 to 122 ± 24 mm Hg (P< 0.05). Large fluctuations in pressure were superimposed on the normal blood pressure waveform during rowing. These rhythmic pressure fluctuations exhibited a one-to-one coupling with stroke rate and were 2–3 times the magnitude of the normal pulse pressure, Thus, theeffective pulse pressureduring the Ist minute of rowing (112 ± 11 mm Hg) was markedly higher (P< 0.01) than the pulse pressure at rest (45 ± 5 mm Hg) and remained so throughout the exercise bout. In five additional subjects in which central venous pressure (CVP) was measured, large stroke-related fluctuations in pressure were also seen in the CVP waveform. Similar fluctuations in blood pressure were observed during repetitive Valsalva mancuvers. These results suggest that the blood pressure response to rowing is principally influenced by a Valsalva-like mancuver performed at the catch of each stroke. The observed arterial pressure fluctuations may explain the degree of myocardial hypertrophy that occurs in the hearts of rowers.

ISSN:0195-9131    

出版商:OVID    

年代:1994

数据来源: OVID