Do sweat calcium losses affect bone mass during firefighter training?

Although participation in vigorous exercise is associated with increased bone mass, recent evidence suggests that loss of calcium in sweat may result in a negative calcium balance and, ultimately, a decrease in bone mass. Anthropometric characteristics, habitual physical activity levels, dietary calcium intake, bone mineral content, and bone turnover markers were measured in 42 male recruits before and after 4 months of firefighter training. During two strenuous mid-training sessions, sweat calcium concentrations were measured; they averaged 1.1 mM. Whole body and total hip bone mineral content increased significantly, as did one marker of bone formation, and were not associated with sweat calcium concentration. This study demonstrates that intense physical training sessions that produce high sweat rates do not have an adverse effect on the bone mineral content of healthy young men.

Long-term exercise and its effect on balance in older, osteoarthritic adults: results from the Fitness, Arthritis, and Seniors Trial (FAST).

OBJECTIVES: To examine the effects of 18-month aerobic walking and strength training programs on static postural stability among older adults with knee osteoarthritis. DESIGN: Randomized, single-blind, clinical trial of therapeutic exercise. SETTING: Both center-based (university) and home-based. PARTICIPANTS: A cohort of 103 older adults (age = 60 years) with knee osteoarthritis who were participants in a large (n = 439) clinical trial and who were randomly assigned to undergo biomechanical testing. INTERVENTION: An 18-month center- (3 months) and home-based (15 months) therapeutic exercise program. The subjects were randomized to one of three treatment arms: (1) aerobic walking; (2) health education control; or (3) weight training. MEASUREMENTS: Force platform static balance measures of average length (Rm) of the center of pressure (COP), average velocity (Vel) of the COP, elliptical area (Ae) of the COP, and balance time (T). Measures were made under four conditions: eyes open, double- and single-leg stances and eyes closed, double- and single-leg stances. RESULTS: In the eyes closed, double-leg stance condition, both the aerobic and weight training groups demonstrated significantly better sway measures relative to the health education group. The aerobic group also demonstrated better balance in the eyes open, single-leg stance condition. CONCLUSIONS: Our results suggest that long-term weight training and aerobic walking programs significantly improve postural sway in older, osteoarthritic adults, thereby decreasing the likelihood of larger postural sway disturbances relative to a control group.

Calcium losses resulting from an acute bout of moderate-intensity exercise.

The purpose of this study was to compare daily calcium (Ca) losses in sweat (S) and urine (U) on an exercise day (E) with losses on the preceding day (i.e., a rest day) during which no exercise (NE) was performed. Ten healthy male volunteers (23.9 +/- 3.2 years) performed a single bout of moderate exercise (running at 80% HRmax) for 45 min in a warm (32 degrees C, 58% relative humidity) environment on E. When E and NE were compared, neither Ca intake (1,232 +/- 714 and 1, 148 +/- 482 mg, respectively) nor urinary Ca excretion (206 +/- 128 and 189 +/- 130 mg, respectively) were different (p >.05). Sweat Ca losses during the exercise bout averaged 45 +/- 12 mg. The results indicate that, although a small amount of Ca is lost in sweat during 45 min of moderate-intensity exercise, measured (sweat and urine losses combined) Ca losses (251 +/- 128 and 189 +/- 130 mg) were not different (p >.05) between days (E and NE, respectively). These data suggest that moderate exercise for up to 45 min in a warm, humid environment does not markedly increase Ca intake requirements.

Acute changes in serum lipids and lipoprotein subclasses in triathletes as assessed by proton nuclear magnetic resonance spectroscopy.

Exercise is associated with changes in lipids that may protect against coronary heart disease (CHD). In this study of 28 triathletes, we analyzed acute changes in serum lipid and lipoprotein concentrations after completion of the 1995 World Championship Hawaii Ironman Triathlon. With standard laboratory assays, we demonstrate significant decreases in total cholesterol, VLDL cholesterol, ApoB100, and Lp(a). Total HDL cholesterol increased significantly immediately after the race. With a novel proton NMR spectroscopy assay, we demonstrate that smaller diameter LDL particles, corresponding to small, dense LDL, declined by 62%. Moreover, larger HDL subclasses, whose levels are inversely associated with CHD, increased significantly by 11%. Smaller HDL subclasses, which have been directly associated with CHD in some studies, acutely decreased by 16%. Therefore, exercise not only acutely induces changes in lipoprotein concentrations among the standard species in a manner that favorably affects CHD risk, but also induces favorable changes in specific lipoprotein subclass size distribution that also may alter CHD risk independently of the total lipoprotein serum concentration.

Hematocrits of triathletes: is monitoring useful?

PURPOSE: The purpose of this manuscript was to provide a basis for establishing safety cutoffs for hematocrit levels in triathletes and background data for possible future medical control regulations. METHODS: Competitors from three different distance triathlons participated: Olympic (N = 118), half-Ironman (N = 87), and Ironman (N = 207). Blood samples were drawn within 24-36 h prerace (N = 412) and within minutes of race finish (N = 296). Prerace hematocrits approximated a normal distribution for men (X = 43.2 +/- 2.9) and women (X = 40.2+/-2.6). Prerace hematocrits decreased as competitive distance increased for men (X = 45.0, 43.4, 42.5; respectively; P < 0.01) but not for women (P > 0.05). RESULTS: Mean race day changes were small but statistically significant for Olympic and Ironman men and for half-Ironman women. Individual responses were more variable with hemoconcentration occurring in 57%, hemodilution in 43%, and no change in 2% of participants. The magnitude of individual responses was also variable with hematocrit changes ranging from -7.1 to + 10%. No athlete in this sample had a hematocrit that would place him/her in the "danger zone" (Hct > 55%). CONCLUSIONS: Cutoff values (3 SD above the means) of 52% for men and 48% for women are suggested by these data. However, the relationship of these cutoffs to either athlete safety or the ability to detect rules violations remains unknown.

Use of heart rate monitors by endurance athletes: lessons from triathletes.

Heart rate monitors are commonly used but little is documented about their use. We have reviewed the available literature and supplemented it with data regarding heart rate responses of a large number of highly trained athletes during cycle ergometer and treadmill exercise tests as well as during and following prolonged exercise. The main findings pertinent to the use of heart rate monitors are 1) estimated maximal heart rates are too variable to be of use to precisely guide training pace during cycling or running, 2) during prolonged (> 6 h) cycling or running, a highly trained athlete may expect to exercise at an average intensity close 80% HRmax, but should also expect intensity to decline by 6-7% during the cycle ride or run, and 3) submaximal exercise heart rates following prolonged exercise are not useful for judging completeness of recovery. This information holds the following implications for athletes wishing to optimize use of their heart rate monitors in training and racing: 1) formal maximal exercise tests should be performed to determine true HRmax in each exercise mode, 2) athletes should expect their heart rates to decrease over the course of a long race, and 3) athletes should not assume they completely recovered from a strenuous workout if submaximal exercise heart rates are unchanged. Much remains to be clarified about the heart rate responses of ultraendurance athletes, particularly in relation to performance and the attainment of individual maximal potential.

Prolonged exercise alters cardiac chronotropic responsiveness in endurance athletes.

OBJECTIVE: To determine whether exhaustive exercise alters cardiac adrenergic chronotropic responsiveness in endurance-trained athletes. METHODS: Fifteen athletes were studied prospectively 2-4 days before and within 3.3 hours after completing the Hawaii Ironman Triathlon (3.9 km swim, 180.2 km bike, 24.2 km run). Increasing intravenous boluses of isoproterenol were given until the rise in heart rate was > 30 bpm (n = 3-6 doses). A log dose heart rate response curve was constructed, and the dose required to increase heart rate by 15 and 25 bpm estimated. Left ventricular size and function were also assessed by echocardiography. RESULTS: After race finish, left ventricular volume (98 vs 83 cc), ejection fraction (56 vs 46%) and diastolic filling (3.86 vs 3.12 edv/sec) were reduced (all p < 0.01). Resting heart rate rose from 54 +/- 7 bpm to 70 +/- 10 bpm. The isoproterenol dose required to increase heart rate by 15 bpm rose from 0.6 to 1.7 micrograms by 25 bpm rose from 1.8 to 4.0 micrograms, both p < 0.01. The linear relationship between change in heart rate and log isoproterenol dose was preserved. CONCLUSIONS: Cardiac chronotropic responsiveness is reduced following an Ironman triathlon.

Left ventricular hypertrophy in athletes.

Left ventricular wall thickness >1.3 cm, septal-to-posterior wall ratios > 1.5, diastolic left ventricular size >6.0 cm, and eccentric or concentric remodeling are rare in athletes. Values outside of these cutoffs in an athlete of any age probably represent a pathologic state.

Estimation of VO2 in older individuals with osteoarthritis of the knee and cardiovascular disease.

The American College of Sports Medicine (ACSM) equation for estimating oxygen consumption (VO2) is often inappropriately applied to non-steady-state treadmill exercise. Therefore, it was the purpose of this investigation to develop an equation to estimate VO2 that could be applied to non-steady-state treadmill exercise in a population of patients with osteoarthritis of the knee, and to assess the generalizability of this equation for estimating VO2peak in patients with cardiovascular disease. Subjects for the investigation were 414 participants in the Fitness and Arthritis in Seniors Trial (FAST), and 362 patients with cardiovascular disease. Results from the FAST subjects showed that the ACSM equation was inappropriate for estimating VO2 during non-steady-state incremental treadmill walking. We developed the following equation (FAST) using speed and the interaction between speed and grade as the predictor variables during treadmill walking: VO2(ml.kg-1.min-1) = 0.0698 x speed(m.min-1) + 0.8147 x grade(%) x speed(m.min-1) + 7.533 ml.kg-1.min-1 The generalizability of the FAST equation for estimating VO2peak was evaluated in the patients with cardiovascular disease. The measured VO2peak of these patients was 23.7 +/- 0.3 ml.kg-1.min-1, whereas the VO2peak values estimated from the FAST equation and the ACSM equation were 24.1 +/- 0.3 and 33.2 +/- 0.5 ml.kg-1.min-1, respectively. No significant differences were found between the measured VO2peak and that estimated from the FAST equation. The VO2peak estimated from the ACSM equation was significantly greater than the measured VO2peak. These results suggest it is more appropriate to use the FAST equation rather than the ACSM equation to estimate VO2 in older patients with either osteoarthritis of the knee or cardiovascular disease.

Applied physiology of triathlon.

The triathlon is a 3-event endurance sport in which athletes compete sequentially in swimming, cycling and running. The primary determinant of success is the ability to sustain a high rate of energy expenditure for prolonged periods of time. Exercise training-induced physiological adaptations in virtually all systems of the body allow the athlete to accomplish this. Aerobic capacity (measured as maximal oxygen uptake, VO2max), economy of motion (submaximal VO2) and fractional utilisation of maximal capacity (%VO2max) reflect the integrated responses of these physiological adaptations. Numerous studies have reported relatively high mean VO2max values for various groups of triathletes that are comparable to those reported for athletes in single-event endurance sports and clearly above those reported for untrained individuals. In shorter distance triathlons and in studies using recreational (rather than elite) triathletes, VO2max is related to performance in the corresponding event of the triathlon (e.g. tethered swimming VO2max with swim time). In longer events and with more elite triathletes, VO2max correlates less well with performance. The physiological adaptations that correspond to and facilitate improved VO2max occur centrally in the cardiovascular system, centred on increased maximal cardiac output, and peripherally in the metabolic systems, centred around increased arterio-venous O2 (a-v O2) difference. While a high VO2max in individuals is clearly of importance to triathlon performance, energy output must be sustained for long periods of time, making economy of motion also very important. Studies suggests that competitive swimmers have better swimming economy than triathletes. However, since many triathletes have previously been competitive swimmers this finding is questionable. The finding suggests that triathletes from nonswimming backgrounds would benefit from improving swimming technique rather than concentrating training workouts solely on distance. In cycling and running, comparison studies have not been done. Economy of motion in swimming, cycling and running have all been found to be correlated with comparable event performance. Training to improve swimming economy can be done without prior exercise, but training to improve swimming economy can be done without prior exercise, but training to improve cycling and running economy should take the multimode nature of a triathlon into consideration. That is, swimming should precede cycling economy training, and cycling should precede running economy training. Cardiovascular, metabolic and neuromuscular adaptations are the main physiological correlates of improved movement economy. Since exercise-induced stress on most physiological systems is based on relative, rather than absolute, exercise intensity, training and racing intensities are frequently quantified as a percentage of maximal capacity of %VO2max.(ABSTRACT TRUNCATED AT 400 WORDS)

Fluid and electrolyte status in athletes receiving medical care at an ultradistance triathlon.

Thirty competitors in the Hawaii Ironman Triathlon were prospectively studied to determine whether fluid and electrolyte disturbances were causes for seeking race-day medical care. Athlete weights were significantly (p < 0.0001) decreased during the race, but decreases were not different in treated (n = 11; % delta wt -2.3 +/- 2.9) versus not treated (n = 19; % delta wt - 2.0 +/- 1.9) athletes. Hyponatremia occurred in nine athletes (30%), and hypomagnesemia in six (20%), but only half of athletes were either electrolyte imbalance sought care. Although athletes receiving medical care may have fluid and electrolyte problems, these abnormalities may also occur in healthy athletes.

Eccentric and concentric muscle performance in patients with spastic paresis secondary to motor neuron disease. A preliminary report.

This study investigated the potential value of eccentric (ECC) and concentric (CONC) isokinetic testing for quantifying motor deficit in patients with spastic paresis secondary to motor neuron disease. We hypothesized that, at a moderately fast (120 degrees s-1) angular velocity, spastic patients would demonstrate different ECC-CONC torque relationships from healthy controls or patients with non-spastic neuromuscular disorders. Eleven patients with motor neuron disease having clinical evidence of spasticity, and 11 disease-control patients (with non-spastic disorders, e.g. lower motor neuron disease or myopathy) underwent isokinetic testing. One healthy subject was matched to each of the 22 patients. The average torque generated during maximal voluntary ECC and CONC knee flexion (KF) and extension (KE) was measured using an isokinetic dynamometer (Kin-Com). Reliability was established (all ICC > or = 0.97) for patient torque measurements. Relative strength (% of control subject torque) in spastic patients was significantly higher for ECC than for CONC actions in both KF and KE; conversely, in non-spastic disease-control patients relative strength was not affected by the type of muscle action. The ECC/CONC average torque ratios for KE and KF at 120 degrees s-1 were significantly greater in spastic patients than controls, but did not differ from controls in non-spastic patients. In spastic patients the ECC-CONC imbalances were related to ambulatory dysfunction. In four spastic patients followed with serial testing, the disproportion between ECC and CONC voluntary capacity persisted over time.(ABSTRACT TRUNCATED AT 250 WORDS)

Eccentric muscle performance of elbow and knee muscle groups in untrained men and women.

Maximal voluntary eccentric (ECC) and concentric (CON) capacity of knee and elbow muscle groups was investigated in healthy untrained men (N = 40) and women (N = 50), 21-67 yr of age. Purposes of the study were to describe torque-velocity and ECC-CON relationships, and to compare these relationships among muscle groups and between genders. Average torque was measured at angular velocities of 30 degrees and 120 degrees.s-1 from knee flexor (KF), knee extensor (KE), and elbow flexor (EF) muscle groups unilaterally, using an isokinetic protocol including gravity compensation. Data were analyzed using ANOVA procedures, and a significance level of 0.01 was used for all hypothesis testing. Torque-velocity relationships were similar for each muscle group and gender; i.e., ECC average torque did not change as a function of velocity and CONC torque decreased as angular velocity increased. Women generated greater ECC relative to CONC torque than men in upper and lower extremity muscle groups. Muscle groups differed in ECC relative to CONC capacity in both men and women, with ECC/CONC ratios being greater for KE and EF than KF. In all muscle groups, the magnitude of ECC-CONC differences increased as angular velocity increased. Genders differed in relative strength balance between muscle groups, with men exhibiting greater KF/KE and EF/KF torque ratios than women for both ECC and CONC actions. Results of this study contribute to the body of women.(ABSTRACT TRUNCATED AT 250 WORDS)

The influence of age on endocrine responses to ultraendurance stress.

BACKGROUND: Aging produces significant changes in the human endocrine system. This study was designed to determine if elderly and younger individuals differ in various endocrine measures before and after ultraendurance stress. METHODS: Sixteen young and 19 older subjects competing in a world championship triathlon had blood samples acquired for 13 hormones before, immediately after the event, and 18 hours into recovery. RESULTS: Following the triathlon, almost every hormone level increased. Significantly higher basal circulating levels of dihydroepiandrosterone sulfate (DHEA-S) and thyroid stimulating hormone (TSH) were found in 20-year-old individuals, whereas higher levels of norepinephrine (NEPI) and sex hormone binding globulin (SHBG) were found in the 50- to 74-year-old group. Older subjects had lower postexercise levels of EPI, DHEA-S, GH, and PRL and higher postexercise levels of estradiol than younger individuals. Similarity in pre- and postrace weights as well as Hgb and Hct levels suggested that dehydration, while present, did not significantly contribute to the endocrine changes. CONCLUSIONS: Ultraendurance stress produced dramatic increases in all but one of the hormones evaluated. Whether frequent exercise can alter the endocrine changes that occur with aging cannot be answered by this study. It is clear, however, that when comparisons are made with young active individuals, frequent exercise does not eliminate the differences in basal concentrations of TSH, DHEA-S, SHBG, and NEPI or exercise-induced release of estradiol, GH, and PRL that occur with aging.

Prevention and treatment of injuries to runners.

1) Many otherwise healthy runners are prevented from participating fully in their chosen endurance sport because of overuse injuries. 2) The most important risk factor for incurring an overuse injury is a training error, such as excessive mileage, sudden change in training distance or intensity, too much hard interval training, improper footwear, and running on chambered surfaces. 3) Although the knee is the most frequent site of injury in runners, any part of the lower extremity may be affected. 4) Tendinitis, muscle strain, and stress fractures are the most common overuse injuries in endurance athletes. 5) Prevention of injury through elimination of risk factors is clearly preferable to treatment. If injury does occur, treatment should include appropriate medical care, athlete education, cross-training, specific rehabilitative exercises, and a programmed return to running.

Regional wall motion abnormalities after prolonged exercise in the normal left ventricle.

To determine whether regional wall motion abnormalities exist or contribute to left ventricular dysfunction, we obtained two-dimensional echocardiograms in 12 athletes before (baseline), immediately after (race finish), and 1 day after (recovery) the Hawaii Ironman Triathlon (a 3.9-km swimming, 180.2-km bicycling, and 42.2-km running event). Left ventricular short-axis and apical four-chamber views were computer digitized and divided into six segments, and radial chord shortening and area ejection fraction were calculated. Global ejection fraction fell at race finish (51% versus 46%, p less than 0.05) but recovered by 1 day (54%, p less than 0.01 by repeated-measures analysis of variance). With the apical four-chamber view, midseptal and apical-septal motion were reduced at race finish but returned to baseline during recovery (midseptal radial chord shortening: 21%, 8%, 22%; apical-septal radial chord shortening: 27%, 12%, 25%; midseptal area ejection fraction: 39%, 30%, 40%; apical-septal area ejection fraction: 44% baseline, 33% race finish, 43% recovery; all p less than 0.01). In contrast, with the parasternal short-axis view, wall motion did not change at race finish but tended to be elevated during recovery and became significant for anteroseptal motion (radial chord shortening: 29%, 30%, 36%; area ejection fraction: 49% baseline, 51% race finish, 58% recovery; both p less than 0.05). Lateral wall motion was unchanged. In addition, an index of septal curvature was calculated using the ratio of the septal-lateral wall minor axis to the perpendicular anteroposterior minor axis. At all three data collections, this ratio remained close to 1.0 at end systole and end diastole.(ABSTRACT TRUNCATED AT 250 WORDS)

Different effects of prolonged exercise on the right and left ventricles.

To examine the functional consequences of the greater increase in right ventricular work with exercise, the effects of prolonged exercise on the right and left heart chambers were compared in 41 athletes before, at the finish (13 min) and after recovery (28 h) from the Hawaii Ironman Triathlon (3.9 km swim, 180.2 km bike ride, 42.2 km run). Two-dimensional and Doppler echocardiograms were analyzed for left and right atrial and ventricular areas at end-diastole and end-systole, right and left ventricular inflow velocities and mitral and tricuspid regurgitation. After exercise, left ventricular and left and right atrial sizes were reduced, whereas right ventricular size increased (diastole: 21.4 to 24.2 cm2; systole: 15.8 to 18.2 cm2; p less than 0.01). The emptying fraction of all chambers was unchanged. Left but not right ventricular inflow showed an increase in peak velocity of rapid filling, whereas both atrial systolic velocities increased (26 to 38 cm/s tricuspid; 38 to 54 cm/s mitral; both p less than 0.01). Overall, the right ventricular early to atrial velocity ratio was reduced after exercise (1.56 to 1.17; p less than 0.05) and the left ventricular pattern was unchanged. The prevalence of tricuspid regurgitation was statistically unchanged (86% to 52%), although that of mitral regurgitation was greatly reduced (76% to 0%). Changes in all variables returned toward prerace values during recovery. Thus, in highly trained athletes, prolonged exercise causes differing responses of the right and left ventricles. These differences may be due to changes in right ventricular function, shape or compliance.

Lactate, oxygen uptake, and cycling performance in triathletes.

To assess the relationship of exercise test variables to each other and to bike race times in an ultra-distance triathlon, we studied 24 participants (14 men, 10 women) in the 1985 Hawaii Ironman Triathlon, using a graded, maximal cycle ergometer test with gas exchange and blood lactate (LA) measurements at each work load. Exercise test variables were oxygen uptake (VO2) and heart rate (HR) at the lactate and ventilatory thresholds. Lactate threshold (LT-1) was defined as the exercise intensity that elicited a 1 mM increase in blood lactate concentration above the value measured during the first work load for each subject. Variables were also examined at the lactate thresholds of 2 mM and 4 mM. Ventilatory thresholds (VT) were identified as the points at which the ventilatory equivalent of oxygen (VE/VO2) increased without a corresponding increase in the ventilatory equivalent of carbon dioxide (VE/VCO2). Mean peak oxygen uptake (peak VO2) for this sample of Ironman triathletes was 57.4 ml.kg-1.min-1. Cycle peak VO2 was inversely correlated, r = 0.68 (P less than 0.0002) with bike finish time. VO2 and HR as well as the respective percentages of maximum were higher at all lactate thresholds than at VT (P less than 0.0001). Therefore VT should not be used to identify a lactate threshold in ultra-endurance triathletes. VO2 values at the lactate and ventilatory thresholds were not highly related to bike finish time (r = -0.26 to -0.58). Fractional utilization of peak VO2 (% peak VO2), HR, and % peak HR at thresholds were not related to bike finish time (r = -0.01 to 0.06).(ABSTRACT TRUNCATED AT 250 WORDS)

Applied physiology of a triathlon.

The triathlon is an endurance contest in which contestants must compete in 3 consecutive events, usually swimming, cycling and running. Success in a triathlon depends upon the ability of the triathlete to perform each of the sequential events at optimal pace without creating fatigue that will hinder performance in the next event. The successful triathlete must, therefore, have highly developed oxygen transport and utilisation systems as well as the ability to efficiently produce a high energy output for prolonged periods without creating metabolic acidosis. Accordingly, mean VO2max values for groups of triathletes during treadmill running have been reported to range from 52.4 to 72 ml/kg/min in men; 58.7 to 65.9 ml/kg/min in women. VO2max values during cycle ergometry were 3 to 6% less than treadmill running values; tethered swimming maximums 13 to 18% less. Predictable and well-known adaptations occur in the cardiovascular systems of triathletes. Structural adaptations of the heart that have been documented in triathletes include increased left ventricular cavity size or wall thickness, or both. Morphological characteristics of the triathlete's heart appear to be unrelated to success in triathlon races. Following the acute stress of triathlon competition, alterations in both systolic and diastolic function have been observed. Heart muscle fatigue is the most likely reason for these changes, since there is a rapid return to normal with rest. Like the cardiovascular system, the musculoskeletal system responds to triathlon training. Peripheral adaptations occur that lead to increased muscle respiratory capacity and to modifications in substrate utilisation. The musculoskeletal system is the site of most injuries to triathletes, and non-traumatic overuse injuries account for 80 to 85% of the musculoskeletal injuries. Maintenance of fluid and electrolyte balance is of primary importance for the triathlete both in day-to-day training and during races. Water may be an adequate replacement fluid for short distance triathlons, but some combination of carbohydrate, electrolyte and fluid replacement is necessary for longer races. Although the physiological bases for success in a triathlon are not well understood at present, the ability to maintain minimal alterations in the homeostasis of cardiovascular, haemodynamic, thermal, metabolic, and musculoskeletal functions are of obvious importance.