摘要:

PYNE, D. B., M. S. BAKER, P. A. FRICKER, W. A. McDONALD, R. D. TELFORD, and M. J. WEIDEMANN.Med. Sci. Sports Exerc., Vol. 27, No. 4, pp. 536–542, 1995. The effects of an intensive 12-wk training program by 12 national-level swimmers on neutrophil oxidative activity were studied. Eleven sedentary (untrained) subjects (6 males and 5 females) served as environmental controls. Blood samples (10 ml) were taken at rest from an antecubital vein and neutrophils isolated by standard separation techniques. The oxidative burst activity of isolated neutrophils was assessed with anin vitroflow cytometric assay that used the fluorescent probe dihydrorhodamine 123. Two-way ANOVA (repeated measures) showed that oxidative activity was lower (P< 0.05) in the elite swimmers compared with the sedentary control group across the 12-wk period. Analysis of cells from swimmers in training was made: repeated measures ANOVA provided evidence of a significant decline (P< 0.05) in the number of cells responding positively toin vitrochallenge. Despite this decline, there was no significant difference in self-reported upper respiratory tract infection rate between the swimmers and sedentary individuals. These data show that: (i) elite swimmers undertaking intensive training have a significantly lower neutrophil oxidative activity at rest than do age- and sex-matched sedentary individuals; (ii) aspects of oxidative activity in swimmers are further suppressed during periods of strenuous training, and (iii) the extent of the suppression does not appear to be of clinical significance.

ISSN:0195-9131    

出版商:OVID    

年代:1995

数据来源: OVID

摘要:

KIRCHNER, E. M., R. D. LEWIS, and P. J. O'CONNOR. Bone mineral density and dietary intake of female college gymnasts.Med. Sci. Sports Exerc., Vol. 27, No. 4, pp. 543–549, 1995. The purposes of this study were to determine bone mineral density (BMD) of female college gymnasts (N= 26) and age- (±1.0 yr), height- (±5.1 cm), and weight- (±2.3 kg) matched controls (N= 26) using dual energy x-ray absorptiometry and to examine the relationship of physical activity, diet, menstrual history, and BMD in these athletes. Energy expenditure, dietary intake and menstruation were assessed using standardized questionnaires. The BMD of the gymnasts were significantly (allP< 0.0001) higher than controls for the lumbar spine (L1–4), total proximal femur, femoral neck, Ward's triangle, and whole body. Mean calcium and kcal intakes for both groups were lower than the Recommended Dietary Allowances, and gymnasts had significantly lower kcal intakes than controls (P< 0.05). More gymnasts than controls (59% vs 24%) reported that their menstrual cycle had been interrupted at some point since menarche (P< 0.02). The major finding of this investigation is that the BMD of gymnasts were higher than matched controls despite the fact that gymnasts as a group had inadequate dietary calcium and a higher propensity to have an interruption of their menstrual cycle.

ISSN:0195-9131    

出版商:OVID    

年代:1995

数据来源: OVID

摘要:

O'CONNOR, P. J., R. D. LEWIS, and E. M. KIRCHNER. Eating disorder symptoms in female college gymnasts.Med. Sci. Sports Exerc., Vol. 27, No. 4, pp. 550–555, 1995. In study 1, 21 females provided both honest and dishonest answers to the Eating Disorders Inventory-2 (EDI-2). It was found that the EDI-2 can be easily faked. The fake profile was used to screen subjects in a second study, in which 25 gymnasts and 25 matched controls were assessed on symptoms of eating disorders, energy intake, menstrual history, and bone mineral density (BMD). A Hotelling's T2test (Wilks' lambda = 0.70) revealed that the gymnast and control groups did not differ significantly (P> 0.05) on the EDI-2 subscales; however, both groups exhibited scores on the Drive For Thinness (DFT) subscale of the EDI-2 that were higher than the published average for college women. More gymnasts (61%) than controls (24%) reported an absence of their menstrual cycle of 3 months or more. A higher percentage (8/11, 73%;X2= 4.7,P< 0.05) of the subgroup with elevated DFT scores (i.e., > 14) reported having this disruption of their menstrual cycle compared with those with lower DFT scores (13/33, 39%). DFT scores were negatively (P< 0.05) related to energy intake (r = −0.48) and whole body BMD (r = −0.47). It is concluded that (a) DFT scores may be useful in identifying gymnasts at risk for problems associated with cating disorders, and (b) response distortion must be considered in future research using the EDI-2.

ISSN:0195-9131    

出版商:OVID    

年代:1995

数据来源: OVID

摘要:

BINDER-MACLEOD, S. A., E. E. HALDEN, and K. A. JUNGLES. Effects of stimulation intensity on the physiological responses of human motor units.Med. Sci. Sports Exerc., Vol. 27, No. 4, pp. 556–565, 1995. Quadriceps femoris muscles were studied in 50 healthy subjects to determine the physiological responses of the motor units recruited at different force levels during transcutancous electrical stimulation. During one set of experiments force-frequency relationships were compared at stimulation intensities that produced tetanic contraction of 20%, 50%, or 80% of the maximum voluntary isometric contraction (MVC). No differences in the normalized force-frequency relationship were observed between the 20% and 50% of MVC conditions and only a slight shift to the left was observed at 80% of MVC. The other set of experiments measured the responses to electrically elicited fatigue tests using frequencies of 20, 40, or 60 pps and, at each frequency, intensities that produced 20% or 50% of MVC. Fatigue was greater for the 50% than 20% MVC force conditions. Within each force level fatigue increased with increasing frequency. However, though the differences in the level of recruitment needed to produce the two forces varied for each frequency, the differences in the amount of fatigue produced at each force did not vary between the three stimulation frequencies. This suggests that the fatigue characteristics of the recruited motor units were similar at all intensities tested. We posit, therefore, that the physiological recruitment order during transcutaneous electrical stimulation is less orderly than previously suggested.

ISSN:0195-9131    

出版商:OVID    

年代:1995

数据来源: OVID

摘要:

KOUTEDAKIS, Y., R. FRISCHKNECHT, G. VRBOVÁ, N. C. C. SHARP, and R. BUDGETT. Maximal voluntary quadriceps strength patterns in Olympic overtrained athletes.Med. Sci. Sports Exerc., Vol. 27, No. 4, pp. 566–572, 1995. Peak torques were studied in 10 clite male overtrained athletes and 10 controls matched for sex, age, sport, and performance level. Isokinetic concentric (CON) and eccentric (ECC) maximal voluntary contractions (MVC) of quadriceps muscle were assessed at the angular velocities of 60°, 120°, and 180°·s-1. Sustained isometric MVCs were also measured at knee angles of 10°, 45°, and 80° of flexion. Six seconds after the beginning of each isometric MVC, a 40-Hz electrical stimulation was superimposed on the MVC for a further 6 s. The overtrained subjects developed significantly smaller CON peak torques at 180°·s-1(P< 0.001), although ECC torques were similar at all three velocities. ECC/CON ratios were higher in the overtrained subjects at 120°·s-1(P< 0.01) and 180°·s-1(P< 0.001) compared with the controls. Isometric MVCs at 10° and 45° knee flexion were lower in the overtrained atP< 0.01 andP< 0.05, respectively. Also in the overtrained subjects, at knee angle of 10°, the addition of the electrical stimulation to the isometric MVC produced an increase (P< 0.05) in torque levels. It is suggested that impaired central drive may account for the present findings.

ISSN:0195-9131    

出版商:OVID    

年代:1995

数据来源: OVID

摘要:

PELTONEN, J. E., J. RANTAMÄKI, S. P. T. NIITTYMÄKI, K. SWEINS, J. T. VIITASALO, and H. K. RUSKO. Effects of oxygen fraction in inspired air on rowing performance.Med. Sci. Sports Exerc., Vol. 27, No. 4, pp. 573–579, 1995. The present study examined the effect the oxygen fraction in inspired air (F2O2) on exercise performance and maximum oxygen consumption (VO2max). Six national level male rowers exercised three 2500-m all-out tests on a Concept II rowing ergometer. Each subject performed one test in normoxia (F2O220.9%), one in simulated hyperoxia (F2O262.2%) and one in simulated hypoxia (F2O215.8%) in a randomized single-blind fashion. The mean final rowing time was 2.3 ± 0.9% (P> 0.01; 95% Cl 1.4–3.2) shorter in hyperoxia and 5.3 ± 1.8% (P> 0.01; 95% Cl 3.1–7.5) longer in hypoxia when compared with normoxia. The effect of F2O2on VO2maxexceeded its effect on exercise performance as VO2maxwas 11.1 ± 5.7% greater (P> 0.01; 95% Cl 5.1–17.1) in hyperoxia and 15.5 ± 3.2% smaller in hypoxia (P> 0.01; 95% Cl 12.2–19.0) than in normoxia. Blood lactate concentration and O2consumption per power unit (ml O2·W-1) failed to indicate statistically significant differences in anaerobic metabolism between normoxia and the other two conditions. These data suggest that there are other parameters besides those of energy metabolism that affect exercise performance as F2O2is modified. These possible mechanisms are discussed in this paper.

ISSN:0195-9131    

出版商:OVID    

年代:1995

数据来源: OVID

摘要:

CHATARD, J.-C, X. SENEGAS, M. SELLES, P. DREANOT, and A. GEYSSANT. Wet suit effect: a comparison between competitive swimmers and triathletes.Med. Sci. Sports Exerc., Vol. 27, No. 4, pp. 580–586, 1995. The purpose of the present investigation was to examine the wet suit effect on 8 swimmers and 8 triathletes. For swimmers, the performances of a 400-m swim with and without wet suit were not statistically different (4 min 12.5 ± 8 s vs 4 min 13.9 ± 4 s) while for triathletes the swim times were reduced by 19 s (4 min 45.8 ± 34 s vs 5 min 04.7 ± 30 s,P> 0.01). For swimmers, VO2max, and blood lactate measured with the wet suit were lower than without (P> 0.01), while for triathletes stroke rate was significantly higher with the wet suit (P> 0.01). For the whole group, the individual differences of performance were related to the blood lactale differences (r = −0.68;P> 0.01) and to the hydrostatic lift (r = 0.63;P> 0.01). For swimmers, the energy cost of swimming and the gliding ability were not statistically different with or without wet suit, while for triathletes they were significantly lower and decreased with velocity. It is concluded that the wet suit effect improves performance more in inefficient swimmers with low buoyancy, swimming at low speeds.

ISSN:0195-9131    

出版商:OVID    

年代:1995

数据来源: OVID

摘要:

VAN LOAN, M. D., N. L. KEIM, K. BERG, and P. L. MAYCLIN. Evaluation of body composition by dual energy x-ray absorptiometry.Med. Sci. Sports Exerc., Vol. 27, No. 4, pp. 587–591. Dual energy x-ray absorptiometry (DXA) measures body composition, tissue distribution, bone mineral content (BMC), and bone mineral density (BMD). Differences are possible due to software versions. This investigation examined body composition, tissue distribution, BMC, and BMD measurements using a DXA (Lunar Corp., Madison, WI) with different software packages (versions 3.4 and 3.6R). Fifteen women, ages 20–40 yr, enrolled in a weight-loss study (body mass index = 28) and volunteered for body composition assessment by densitometry. BMC, BMD, and tissue distribution measurements were made using DXA. Results were analyzed once each with software versions 3.4 and 3.6R. BMC + total soft tissue, measured using DXA, was comparable to measured body weight (3.4 = 76.3 kg; 3.6R = 76.5 kg; weight = 76.5 kg). Lower BMC and BMD (5.5% and 1.8%,P> 0.01) were observed with 3.6R. Arm tissue mass was lower (1,530 g;P> 0.01) and fat declined (1,069 g;P> 0.01) with 3.6R. Leg tissue mass decreased 487 g (P> 0.01), but fat tissue increased (526 g,P> 0.01) with 3.6R. A larger fat mass (1,492 g) and lower lean mass (1,115 g) were observed with 3.6R compared with 3.4. Percent fat values by densitometry using DXA 3.4 and 3.6R were 38.1%, 39.9, and 41.9%, respectively. These results demonstrated differences in total body composition, lean and fat tissue distribution, and bone measurements from DXA software versions.

ISSN:0195-9131    

出版商:OVID    

年代:1995

数据来源: OVID

摘要:

HOPKINS, W. G. and J. R. GREEN. Combining event scores to estimate the ability of competitors. Med. Sci. Sports Excrc., Vol. 27, No. 4, pp. 592–598, 1995. Simulation was used to investigate the validities of nine measures of ability derived from scores of two or more competitive events. The measures were: raw means and least-squares means of raw scores, z scores, and normal scores; two measures derived from ranked scores; and the “personal-best” raw score. Simulations were performed for different numbers of competitors, events, and event entries, each for a range of validity of performance in a single event. A complete set of simulations was repeated for each of the following conditions: normal distribution of competitors' ability; skewed distribution of ability; event validity related to ability; validity, ability, and spread of scores differing between events; and events differing in difficulty. The raw mean of raw scores was generally the most valid measure. The personal best was comparable to the mean only when the number of entries approached one per competitor. The least-squares mean of raw scores had highest validity when events differed substantially in difficulty; it should therefore be used when events differ in length, or when event scores are affected by environmental conditions, judging bias, or by uneven matching of competitors in match-play sports.

ISSN:0195-9131    

出版商:OVID    

年代:1995

数据来源: OVID

摘要:

HEIL, D. P., P. S. FREEDSON, L. E. AHLQUIST, J. PRICE, and J. M. RIPPE. Nonexercise regression models to estimate peak oxygen consumption.Med. Sci. Sports Exerc., Vol. 27, No. 4, pp. 599–606, 1995. The purpose of this study was to develop a VO2peakprediction model derived from nonexercise (N-EX) based predictors. VO2peakwas measured using a walking treadmill protocol with 229 females and 210 males between 20 and 79 yr of age (mean ± SD: 38.62 ± 10.36 ml·kg-1·min-1). Subjects were randomly divided into validation (V) (85% of total;N= 374) and cross-validation (CV) (15% of total;N= 65) groups. The V group was used to validate generalized and gender-specific models using stepwise multiple regression procedures with gender, age and age, percent body fat, and a physical activity code (AC). The generalized ml·kg-1·min-1(R2= 0.77, SEE = 4.90 ml·kg-1·min-1, SEE% = 12.7%) and gender-specific (females: R2= 0.72, SEE = 4.64 ml·kg-1·min-1males: R2= 0.72, SEE = 5.02 ml·kg-1·min-1) models were highly accurate relative to N-EX and exercise based models in the literature. Cross-validation procedures were used to evaluate model stability. The generalized model was stable across the total CV group and various CV subsamples (by gender, decade-wide age groups, and AC groups), but not across groups similar in VO2peak. These results suggest that N-EX models can be valid predictors of VO2peakfor heterogenous samples.

ISSN:0195-9131    

出版商:OVID    

年代:1995

数据来源: OVID