The effect of vitamin D and frailty on mortality among non-institutionalized US older adults.

BACKGROUND/OBJECTIVES: Although both frailty and low vitamin D have been separately associated with an increased risk for adverse health, their joined effects on mortality have not been reported. The current study examined prospectively the effects of frailty and vitamin D status on mortality in US older adults. SUBJECTS/METHODS: Participants aged ≥ 60 years in The Third National Health and Nutrition Examination Survey with 12 years of mortality follow-up were included in the analysis (n=4731). Frailty was defined as meeting three or more criteria and pre-frailty as meeting one or two of the five frailty criteria (low body mass index (BMI), slow walking, weakness, exhaustion and low physical activity). Vitamin D status was assessed by serum 25-hydroxyvitamin D (25(OH)D) and categorized into quartiles. Analyses were adjusted for gender, race, age, smoking, education, latitude and other comorbid conditions. RESULTS: Serum 25(OH)D concentrations were lowest in participants with frailty, intermediate in participants with pre-frailty and highest in participants without frailty. The odds of frailty in the lowest quartile of serum 25(OH)D was 1.94 times the odds in the highest quartile (95% confidence interval (CI): 1.09-3.44). Mortality was positively associated with frailty, with the risk among participants who were frail and had low serum 25(OH)D being significantly higher than those who were not frail and who had high concentrations of serum 25(OH)D (hazards ratio 2.98; 95% CI: 2.01-4.42). CONCLUSION: Our results suggest that low serum 25(OH)D is associated with frailty, and there is additive joint effects of serum 25(OH)D and frailty on all-cause mortality in older adults.

Comparison of stretching with ice, stretching with heat, or stretching alone on hamstring flexibility.

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.

Muscular fatigue patterning in power grip assessment.

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.

Measurement of body composition in the elderly: dual energy x-ray absorptiometry, underwater weighing, bioelectrical impedance analysis, and anthropometry.

Body composition of both younger and older subjects was estimated using several different methods in order to evaluate their use with elderly subjects. Estimates were obtained by dual energy x-ray absorptiometry, underwater weighing, bioelectrical impedance analysis, and skinfold measurement in 48 younger subjects (26-40 years) and 44 older subjects (65-85 years). In older men and women the underwater weighing percent fat estimates were significantly higher than all other methods. Bone mineral explained a significant proportion of the variance in the difference between the dual energy x-ray absorptiometry and underwater weighing estimates of percent fat (R2 = 0.442-0.627). Because of its insensitivity to variability in bone mineral, we recommend that the underwater weighing method be not used to estimate percent fat in older men and women. Dual energy x-ray absorptiometry provides an alternative which accounts for the age-related decrease in bone mineral density.

The relationship between two power-grip testing devices and their utility in physical capacity evaluations.

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.

Exercise training, indomethacin, and isoproterenol-induced myocardial necrosis in the rat.

It was hypothesized that endurance exercise training would attenuate isoproterenol-induced myocardial necrosis in the rat by increasing the concentration of prostacyclin in the myocardial vasculature. Rats were randomly assigned to exercise and control groups. Exercisers ran on a motorized treadmill 1 h.d-1, 5 d.week-1 for 14 weeks. Immediately following the training program subgroups of rats were injected with 4 mg.kg-1 indomethacin or saline. One day later, all rats were given a subcutaneous injection of isoproterenol (20 mg.kg-1); after another 24 h they were sacrificed. A decrease of myocardial creatine kinase (CK) activity was used as a marker for myocardial necrosis. Endurance exercise training attenuated the isoproterenol-induced decrease in myocardial CK relative to control by approximately 37% (exercise: 16.4 +/- 0.6 U.mg-1 protein; control: 10.5 +/- 0.6 U.mg-1 protein; p less than 0.05). Pretreatment with indomethacin decreased myocardial CK in the exercise-trained rats (indomethacin: 15.4 +/- 0.8 U.mg-1 protein; saline: 17.7 +/- 0.7 U.mg-1 protein; p less than 0.05), but not in the controls (indomethacin: 10.3 +/- 1.0 U.mg-1 protein; saline: 10.8 +/- 0.6 U.mg-1 protein; p greater than 0.05). The concentration of myocardial 6-keto-PGF1 alpha, a marker for prostacyclin, was not altered by exercise but, as expected, was reduced by indomethacin pretreatment (p less than 0.05). Thus, exercise training reduces myocardial damage caused by isoproterenol, but the evidence does not support the hypothesis that prostacyclin mediated this effect of training. Further research is needed to determine the extent to which exercise training-induced alterations in sensitivity to PGI2 or TXA2 affect myocardial damage from isoproterenol.(ABSTRACT TRUNCATED AT 250 WORDS)

Effect of toeclip use during cycle ergometry on ventilatory threshold and VO2 max in trained cyclists and runners.

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.

Indomethacin suppresses the coronary flow response to hypoxia in exercise trained and sedentary rats.

STUDY OBJECTIVE: The aim was to determine if prostaglandin like activity might be involved in changes due to exercise training in the coronary flow responses to hypoxia. DESIGN: The coronary flow response to hypoxia was measured under constant perfusion pressure in isolated perfused hearts from 12 endurance exercise trained rats and 12 control rats. Eight hearts were perfused with a solution containing indomethacin, a cyclo-oxygenase inhibitor, to determine its effect on any training induced changes in the coronary flow response to hypoxic stress. EXPERIMENTAL MATERIAL: 24 male Sprague-Dawley rats, 517 (SD 51) g, were used for this study. The animals were anesthetised and the hearts rapidly excised and perfused with a modified Langendorff perfusion system. MEASUREMENTS AND MAIN RESULTS: Under constant perfusion pressure, the hearts of endurance exercise trained rats had a greater increase in coronary flow during hypoxia relative to normoxia than did hearts of untrained rats, at 13.52(2.15) v 9.56(1.05) ml.min-1.g-1 dry heart weight. Indomethacin treatment abolished this difference and lowered coronary flow: exercise -3.81(3.75) ml.min-1.g-1; control 0.38(2.44) ml.min-1.g-1. CONCLUSIONS: The inhibition by indomethacin of the endurance exercise training induced potentiation of the coronary fluid flow response to hypoxia suggests that prostacyclin or a related compound may be involved in this adaptation to exercise.

Estimating physical working capacity and training changes in the elderly at the fatigue threshold (PWCft).

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.

Optimal use of fluids of varying formulations to minimise exercise-induced disturbances in homeostasis.

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)