Automated physical activity monitoring: validation and comparison with physiological and self-report measures.

Physical activity can be assessed via self-report, via physiological measures such as heart rate and oxygen uptake, or via automated monitor. An electronic accelerometer-based physical activity device (Actigraph) has been reported as an improvement over other activity measurement techniques in terms of utility and accuracy. Four studies provide systematic validation and reliability testing for this device and comparisons with other techniques for assessing daily activities. In the first study, the sensitivity of the Actigraph was determined for differentiating physical activities (walking, running, stair climbing, knee bends) versus sedentary activities (reading, typing, playing video games, and performing a mental arithmetic task). Fifteen healthy adults wore the Actigraph on their wrist during activities; oxygen uptake and heart rate were simultaneously recorded. Results revealed that the Actigraph significantly differentiated between the physical activities (p < .0001) and the sedentary activities (p < .0001). Actigraph counts also correlated significantly with oxygen uptake (r = .73) and heart rate (r = .71) during physical activities (r = .46) and sedentary activities (r = .35), respectively. Test-retest reliability was very high for 12 activities (r = .98). The high level of activity differentiation and strong relationship to oxygen uptake and heart rate suggest the usefulness of this device for behavioral and biomedical studies. However, these studies also indicate that the wrist may not always be the most adequate placement for indexing rate and intensity of daily activities and that further studies are needed to determine the optimal site of monitor attachment. Advantages and disadvantages of self-report, physiological, and automated measures of activity are discussed.

Effects of antihistamine medications on exercise performance. Implications for sportspeople.

The athlete who suffers from atopic diseases such as seasonal allergic rhinitis has an arsenal of antihistamines from which to choose for relief of symptoms. The decision to select a particular medication involves consideration of its efficacy and its side effects. Many of the standard antihistamines have sedative side effects which render them undesirable for use by athletes during competition. For example, a survey of studies suggests that some of these medications may compromise the performance of psychomotor skills important to the athlete (e.g. reaction time and visual discrimination). The newer, nonsedating antihistamines are equal to the standard agents in efficacy and comparable with placebo in central nervous system effects. Thus, psychomotor performance is not adversely affected by the newer antihistamines. Despite their widespread use, the effects of treatment with antihistamines on exercise performance (e.g. metabolic responses and time to exhaustion) have scarcely been addressed. The few studies available indicate that single oral administrations of antihistamines neither compromise nor enhance exercise performance or tolerance in asymptomatic individuals. Yet the research conducted has not examined the effects of antihistamine ingestion on exercise performance in symptomatic individuals. Whether treatment with an antihistamine would improve exercise performance relative to nontreatment in symptomatic, atopic athletes remains to be determined. Whereas there is a dearth of information on the effects of antihistamine medications on exercise performance, there is growing evidence that pretreatment with antihistamines may prevent or attenuate some exercise-induced histamine-mediated disorders such as urticaria, pruritus, anaphylaxis and gastrointestinal bleeding. A survey of studies suggests that prophylactic treatment with antihistamines may increase tolerance to exercise in individuals susceptible to these disorders.

Ingestion of an antihistamine does not affect exercise performance.

The effects of a single oral dose of a sedating and nonsedating H1 receptor antagonist on exercise performance and tolerance were examined in a double-blind, randomized study. Twelve healthy, physically active subjects were tested under a placebo condition and two antihistamine conditions (diphenhydramine hydrochloride (50 mg) and terfenadine (60 mg)). The following treadmill exercise tests were administered: maximal aerobic power (MAX), submaximal steady state (SS), and high-intensity, intermittent exercise (HI). The MAX test consisted of incremental treadmill running to volitional exhaustion. For the SS test, subjects ran for 30 min on the treadmill at approximately 55% of their VO2max. The HI test consisted of alternated 30-s bouts of running and rest to volitional exhaustion; the treadmill grade was 10% and the intensity was nearly 90% of VO2max. Measures of oxygen uptake, heart rate, rectal temperature, post-exercise plasma lactate concentration, and time on treadmill for the MAX and HI tests were compared across treatment conditions. There were no statistically significant differences in performance measures across treatment conditions. The results indicate that a single dose of antihistamine will neither compromise nor improve aerobic and glycolytic work performance under these exercise conditions.

Acute antihistamine ingestion does not affect muscle strength and endurance.

Twelve subjects (three females, nine male, age 32 +/- 1.3 yr) performed tests of isokinetic muscle strength and endurance under each of three treatment conditions. The three conditions, administered in double-blind, randomized order, were single oral administrations of placebo, diphenhydramine (50 mg), and terfenadine (60 mg). Tests, separated by 1 wk, began 2 h after ingestion of the drug or a placebo. Subjects performed a velocity spectrum test (VST) consisting of peak torque measurements at five velocities (90, 150, 210, 270, and 330 degrees.s-1) and a 45 s muscle endurance test (MET) at a velocity of 180 degrees.s-1. Five serial, reciprocal contractions of the knee extensors and flexors were performed at maximal effort over the subjects' full range of motion for the VST, and as many contractions as possible within 45 s for the MET. No differences in performance measures were detected across treatment conditions. This study demonstrates that a one-time administration of either terfenadine or diphenhydramine in the dosages described does not significantly affect muscle endurance or maximal peak torque at a variety of velocities.

Fluid and cation changes during head-out immersions in 25 degrees and 35 degrees C water.

To compare fluid and ion changes during cold (25 degrees C) and thermoneutral head-out immersion (HOI) 9 men were studied under 4 resting conditions lasting 3 h: 2 in 35 degrees C and 2 in 25 degrees C water. At each temperature, subjects consumed 250 ml of either water or a 7% glucose polymer solution every hour to evaluate possible differences in fluid composition. Plasma volume increased by 3.9% for 35 degrees C and decreased by 9.7% for 25 degrees C HOI after 3 h. Urine flow increased significantly during HOI, but there were no differences between water temperatures (35 degrees C: 8.37 +/- 0.44; 25 degrees C: 9.55 +/- 0.57 ml.min-1). Free water clearance and urinary sodium excretion were also elevated during HOI, but water temperature did not alter the magnitude of the response. No HOI-induced kaliuresis was noted. Finally, there was a significant cold-induced increase in serum potassium and sodium, but this reflected largely the decrease in plasma volume. In sum, differences in water temperature seemed to have minimal influence on fluid and cation changes, an indication that immersion is the primary stimulus. Whether greater differences would be noted with colder water remains to be determined.

Orthopedic history and examination in the etiology of overuse injuries.

Overuse injuries, and stress fractures in particular, afflict many runners and military recruits. This investigation sought to identify pretraining factors which may predispose to overuse injuries. Orthopedic and running history questionnaires and an orthopedic examination were administered to 505 trainees entering an intensive military training school. A novel method for evaluating ankle dorsiflexion was developed, and alignment measures, in units of centimeters rather than degrees, were obtained. Over 10% of the trainees were removed from the school for overuse-related injuries, and over half of these were tibial stress fractures. The incidence of clinically diagnosed stress fractures was 6.3%. No single orthopedic history question or combination of questions could discriminate between trainees who did or did not subsequently incur overuse injuries. Results from the running history indicated that those running 25 or more miles.wk-1 (mpw) had a significantly (P less than 0.027) lower incidence of stress fractures (3.0%) than those running 4 or fewer mpw over the previous year (11.5%). The orthopedic examination did not identify any predisposing alignment characteristics, perhaps due to the low incidence of overuse injuries. Population means are presented for future use in comparative studies.

Hormonal and metabolic responses of untrained, moderately trained, and highly trained men to three exercise intensities.

Untrained, moderately trained (runners, 15 to 25 mi/wk), and highly trained (runners, greater than 45 mi/wk) men participated in graded treadmill exercise at 50%, 70%, and 90% of their maximal oxygen consumption to quantify the relation between intensity of exercise and sympathetic nervous system and metabolic responses. Sympathetic system activation was noted at all intensities tested and was proportional to the relative exercise intensity. The magnitudes of the norepinephrine (NE) and epinephrine (E) responses were similar in all three groups of men at each relative exercise intensity and correlated with the magnitudes of change in levels of circulating plasma adrenocorticotropin hormone, cortisol, lactate (La), phosphate (Pi), and glucose (GI). The magnitudes of change in concentrations of La, Pi, and GI were also similar for the three groups at each relative exercise intensity. In contrast, a lower degree of sympathetic system activation in response to a given absolute workload was noted in the moderately and highly trained men as compared to that of the untrained men. Sympathetic and metabolic responses to exercise are similar under conditions of comparable relative exercise intensities, regardless of conditioning level. The sympathetic-adrenal medullary system is more sensitive to exercise than the hypothalamic-pituitary-adrenal axis. For a given absolute workload, the degree of activation significantly lower in trained individuals.

Prolonged whole-body cold water immersion: fluid and ion shifts.

To characterize fluid and ion shifts during prolonged whole-body immersion, 16 divers wearing dry suits completed four whole-body immersions in 5 degrees C water during each of two 5-day air saturation dives at 6.1 msw. One immersion was conducted at 1000 (AM) and one at 2200 (PM) so that diurnal variations could be evaluated. Fifty-four hours separated the immersions, which lasted up to 6 h; 9 days separated each air saturation dive. Blood was collected before and after immersion; urine was collected for 12 h before, during, and after immersion for a total of 24 h. Plasma volume decreased significantly and to the same extent (approximately 17%) during both AM and PM immersions. Urine flow increased by 236.1 +/- 38.7 and 296.3 +/- 52.0%, urinary excretion of Na increased by 290.4 +/- 89.0 and 329.5 +/- 77.0%, K by 245.0 +/- 73.4 and 215.5 +/- 44.6%, Ca by 211.0 +/- 31.4 and 241.1 +/- 50.4%, Mg by 201.4 +/- 45.9 and 165.3 +/- 287%, and Zn by 427.8 +/- 93.7 and 301.9 +/- 75.4% during AM and PM immersions, respectively, compared with preimmersion. Urine flow and K excretion were significantly higher during the AM than PM. In summary, when subjects are immersed in cold water for prolonged periods, combined with a slow rate of body cooling afforded by thermal protection and enforced intermittent exercise, there is diuresis, decreased plasma volume, and increased excretions of Na, K, Ca, Mg, and Zn.

Reliability of an isokinetic test of muscle strength and endurance.

Funding for this study was provided by the U.S. Army Medical Research and Development Command, Project No. 85PP5866, under the Joint Working Group on Drug Dependent Degradation in Military Performance Program. The opinions or assertions contained herein are private ones of the authors and are not to be construed as official or reflecting the views of the Department of Defense or the Uniformed Services University of the Health Sciences. The reliability of an isokinetic test of muscle strength and endurance was evaluated. Eleven males and 9 females underwent testing on three separate occasions, 2-4 days apart. The protocol included a velocity spectrum test (VST-5 repetitions at velocities ranging from 90-330 degrees /sec) and a muscle endurance test (number of contractions performed in 45 sec at 180 degrees /sec). In the VST, no significant within-subject test day differences were noted at any velocity. Reliability was generally higher at slower velocities and higher for knee extension than flexion. Mean intraclass correlation coefficients (ICCs) for peak torque across velocities were 0.88 for extension and 0.79 for flexion. For the endurance test, two reliable measures were total work performed and average power (ICCs = 0.92); relative endurance measures had ICCs of less than 0.80. Thresholds for demonstrating experimental effects and the number of subjects to test at different detection levels are-recommended.J Orthop Sports Phys Ther 1989;10(8):315-322.

Acute hypothalamic-pituitary-adrenal responses to the stress of treadmill exercise. Physiologic adaptations to physical training.

To study the effects of physical conditioning on the hypothalamic-pituitary-adrenal axis, we examined the plasma ACTH, cortisol, and lactate responses in sedentary subjects, moderately trained runners, and highly trained runners to graded levels of treadmill exercise (50, 70, and 90 percent of maximal oxygen uptake) and to intravenous ovine corticotropin-releasing hormone (1 microgram per kilogram of body weight). Basal evening concentrations of ACTH and cortisol, but not of lactate, were elevated in highly trained runners as compared with sedentary subjects and moderately trained runners. Exercise-stimulated ACTH, cortisol, and lactate responses were similar in all groups and were proportional to the exercise intensity employed. These responses, however, were attenuated in the trained subjects when plotted against applied absolute workload. Only the highly trained group had diminished responses of ACTH and cortisol to ovine corticotropin-releasing hormone, consistent with sustained hypercortisolism. We conclude that physical conditioning is associated with a reduction in pituitary-adrenal activation in response to a given workload. Alterations of the hypothalamic-pituitary-adrenal axis consistent with mild hypercortisolism and similar to findings in depression and anorexia nervosa were found only in highly trained runners. Whether these alterations represent an adaptive change to the daily stress of strenuous exercise or a marker of a specific personality profile in highly trained athletes is unknown.