Search

Purpose: To examine whether there are differences between demographic, behavioral, and biological variables for those with invalid accelerometry data (IAD) and those with valid accelerometry data (VAD)., Design: Cross-sectional., Setting: Data from 2003-2006 National Health and Nutrition Examination Survey (NHANES) were used., Subjects: Participants included 1,315 children (i.e., 6-11 years) with VAD and 534 children with IAD and 1,859 adolescents (i.e., 12-17 years) with VAD and 1,057 with IAD., Measures: Physical activity (PA) was measured using an accelerometer, with questionnaires used to assess demographic and behavioral variables and biological parameters assessed from a blood sample., Analysis: Wald and design-based likelihood ratio tests and logistic regression were used to assess differences between those subjects with IAD and those with VAD., Results: After adjustments, overweight children, compared to normal weight children, were 1.6 (odds ratio [OR] = 1.67; 95% confidence interval [CI]: 1.22-2.29) times more likely to have IAD. After adjustments, and as an example, adolescents engaging in 4 or more hours of computer use per day, compared to no computer use, were 2.6 (OR = 2.6; 95% CI: 1.38-5.18) times more likely to have IAD., Conclusion: Excluding youth with IAD may introduce bias, limit generalizability, and ultimately underestimate the association between PA and health outcomes. Future research is needed to identify reasons for poor monitoring compliance.

Objective: To investigate the efficacy of stretching with ice for increasing hamstring flexibility., Design and Setting: Supine hamstring flexibility was measured before and after subjects accomplished a 20-minute hamstring stretching routine. Two groups of eight subjects accomplished the routine using one of two modalities. A control group (n = 8) accomplished the routine without a modality. The measurements were compared., Subjects: Twenty-four male collegiate baseball players., Measurements: Heat or ice applied to the hamstring., Results: We found differences in the responses among subject groups. Supine hamstring flexibility after stretching with ice was greater than both stretching with heat and stretching alone. Scores after stretching with heat and stretching alone were not different., Conclusions: The results of our investigation suggest that the application of ice may provide enhanced short-term improvements in hamstring flexibility over heat or stretching alone. Further research is necessary to investigate the possible mechanisms for these improvements and to determine whether similar results can be obtained with other muscle groups.

Physical fatigue has been identified as a risk factor associated with the onset of occupational injury. Muscular fatigue developed from repetitive hand-gripping tasks is of particular concern. This study examined the use of a maximal, repetitive, static power grip test of strength-endurance in detecting differences in exertions between workers with uninjured and injured hands, and workers who were asked to provide insincere exertions. The main dependent variable of interest was power grip muscular force measured with a force strain gauge. Group data showed that the power grip protocol, used in this study, provided a valid and reliable estimate of wrist-hand strength-endurance. Force fatigue curves showed both linear and curvilinear effects among the study groups. An endurance index based on force decrement during repetitive power grip was shown to differentiate between uninjured, injured, and insincere groups.

This study compared two isometric-grip testing devices and considered the efficacy of combining data from the two as a means of identifying both functional status and consistency of effort for physical capacity evaluations (PCEs). Two groups (26 healthy subjects and 40 patients who had upper-extremity impairments) were used to establish the reliability of applying force on a jamar dynamometer, and on an Isometric Strength Testing Unit (ISTU). Many of the patients had been referred because of inconsistencies between subjective complaint and medical presentation. The results indicate that power-grip force outputs are highly related across the two test devices, which validates their utility as part of a PCE for wrist-hand involvement. A simple index (2-ratio) of functional status and consistency was developed by combining test data from the two devices. The sensitivity of the 2-ratio, in combination with other indices of consistency, is discussed.

The purpose of this study was to investigate the effects of the use of toeclips on the ventilatory threshold (VT) of cyclists and runners during cycle ergometry. Ten competitive cyclists and ten well-trained runners performed two continuous maximal cycle ergometer tests, once with toeclips and once without toeclips. Respiratory data were collected every 20 s and used to determine VT and VO2 max. For cyclists, the mean (congruent to SEM) oxygen uptake at VT (VO2, VT) was greater during the trial with toeclips (48.8 +/- 1.9 ml kg-1 min-1 and 46.9 +/- 1.9 ml kg-1 min-1 during cycle ergometry with and without toeclips, respectively; p less than 0.05). No significant difference in VO2, VT was noted between trials for runners. The cyclists also demonstrated a higher VO2 max during the trial with toeclips (58.8 +/- 3.0 ml kg-1 min-1) compared to the trial without toeclips (54.4 +/- 2.0 ml kg-1 min-1; p less than 0.05). When expressed relative to VO2 max (%VO2 max) the VT during the toeclip trial for cyclists was significantly decreased (p less than 0.05). These data suggest that the cyclists in this study developed specific adaptations related to the use of toeclips, and the use of toeclips during cycle ergometry is therefore recommended. We recommend that future studies report results with VT expressed in both absolute (VO2) and relative (%VO2 max) terms.

The rationale underlying the development of various formulations of beverages for consumption before, during, and/or after physical exercise is that such formulations should minimise some of the disturbances in physiological homeostasis that occur during exercise and thereby prevent injury and/or enhance performance. Exercise- and dehydration-induced increases in core temperature, body fluid osmolality, heart rate, losses of plasma and other body fluid volumes, and carbohydrate depletion are probably the most important homeostatic disturbances that can be ameliorated by fluid consumption. With the exception of athletes subject to hyponatraemia after consumption of ordinary water during prolonged activity, changes in electrolyte concentrations in the body fluids of most athletes do not justify the inclusion of electrolytes in fluid replacement beverages to be consumed during exercise. However, small amounts of sodium added to water does speed gastric emptying and fluid absorption from the intestine. Recent evidence suggests that a precompetition meal high in easily digested carbohydrates should be consumed not later than 5 to 6 hours before competition. There is little published research on the optimal composition of this meal. Water ingestion 30 to 60 minutes before exercise seems to be of benefit to temperature regulation and cardiovascular homeostasis if the exercise is of moderate intensity (50 to 65% VO2max), but probably has little effect at the higher intensities of athletic performance. There is no systematic evidence to support the inclusion of calcium or sodium chloride in drinks consumed an hour or 2 before exercise. Furthermore, if glucose solutions are fed 15 to 45 minutes before prolonged exercise, they will probably cause a fall in blood glucose during exercise and may adversely affect performance. These adverse effects are not present when fructose is consumed before exercise. Contrary to the adverse effects of glucose feedings 15 to 60 minutes before exercise, the consumption of 18 to 50% solutions of glucose or glucose polymers 5 minutes before prolonged exercise seems to have potential for improving endurance performance. Similarly, the inclusion of caffeine in beverages consumed 60 minutes before prolonged exercise improves athletic performance for many subjects. Others may be hypersensitive to the effects of caffeine and are adversely affected by its use. For exercise leading to exhaustion in less than 30 minutes, neither caffeine nor carbohydrate ingestion is effective in minimising homeostatic perturbations or improving exercise performance.(ABSTRACT TRUNCATED AT 400 WORDS)

The test for estimating physical working capacity at the fatigue threshold (PWCft), previously validated for young men, was evaluated for use with elderly men and women. A sample of 27 volunteer subjects (67.6 +/- 5.6 years, 11 male, 16 female) was divided into three matched groups: (1) controls (n = 10), (2) low intensity (70% PWCft) training group (n = 10) and (3) high intensity (85% PWCft) training group (n = 7). The subjects were tested for PWCft before and after 10 weeks of exercise training on cycle ergometers (30 min/day, 3 days/week). Controls did not exercise but met once a week for a health lecture. No significant pre-test to post-test change was noted in the mean PWCft of the control group (78.8-78.5 W); low intensity training resulted in 29.8% improvement in PWCft (81.0 to 105.0 W); and the high intensity group realized an improvement of 38.4% (83.6-115.7 W). One-way ANOVA indicated that the gains made by each of the groups were significantly different (p less than 0.01). Post hoc analysis revealed that the gains made by each exercise training group were significantly greater than controls (p less than 0.05) with no significant difference between high and low intensity groups. Reproducibility of the PWCft was excellent (R = 0.976). Since RPE averaged 14.2 at PWCft and 64% of subjects provided useful data, this test appears to be useful for evaluating the fitness of the elderly.

This study determined the effects of consuming three different amounts of liquid carbohydrate 4 h before exercise on the metabolic responses during exercise and on exercise performance. Four hours before exercise subjects consumed either 45 (L) or 156 (M) g of carbohydrate in isocaloric feedings and either 0 (P) or 312 (H) g of carbohydrate. Interval cycling was undertaken for 95 min, followed by a performance trial. Blood glucose had reached basal 1 h after all feedings; blood insulin had reached basal 3 h after ingestion of P, L, and M but was still 84% higher for H at the start of exercise. During exercise insulin averaged 48% higher for H than P. Blood glucose decreased 16% during exercise for P, L, and M, whereas for H there was a transient drop the first 15 min of exercise, after which glucose increased and remained constant throughout exercise. More carbohydrate oxidation occurred during exercise for H vs P, whereas results were similar for L and M. Ingestion of H improved performance by 15% as compared with P, whereas performance was similar for L and M. These results indicate that, despite elevated insulin at the start of and during exercise, consumption of 312 g of carbohydrate 4 h before moderately intense prolonged exercise can improve performance, perhaps via an enhancement of carbohydrate oxidation.