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.

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)

Left ventricular structure and function by echocardiography in ultraendurance athletes.

To determine left ventricular (LV) structural and functional changes induced by ultraendurance exercise training, M-mode LV echograms and Doppler recordings of LV inflow velocity in 26 triathletes and 17 normal subjects were studied. All triathletes trained 20 to 40 hours/week in swimming, cycling and running for more than 2 years. Structurally, triathletes had normal LV systolic and diastolic cavity dimensions, but increased wall thickness (1.05 +/- 0.26 vs 0.80 +/- 0.27 cm in normal subjects, p less than 0.001), increased relative wall thickness, or h/R ratio (0.41 +/- 0.10 cm vs 0.33 +/- 0.11 cm in normal subjects, p less than 0.001), and increased LV mass (226 +/- 60 vs 143 +/- 54 g in normal subjects, p less than 0.001). LV mass correlated closely with mean exercise blood pressure during an 8-hour exercise test in 14 triathletes (r = 0.88). Systolic function at rest was similar in both groups, with no differences in fractional shortening or end-systolic stress. Diastolic LV function measured by digitized M-mode echo was similar in normal subjects and triathletes, with no differences in peak rates of cavity enlargement and wall thinning by echocardiogram. In contrast, the Doppler-derived ratio of early-to-late LV inflow velocities was slightly increased in triathletes (p less than 0.05). It is concluded that ultraendurance training produces a physiologic pattern of moderate pressure overload LV hypertrophy, in proportion to the hemodynamic load imposed during prolonged exercise. Unlike the abnormal hypertrophy of systemic hypertension, early diastolic function remains normal in the triathlete heart.

Prevalence of multivalvular regurgitation in athletes.

To assess the effects of exercise training on the prevalence of valvular regurgitation, 2-dimensional echocardiography and Doppler flow mapping were performed in 45 athletes and 26 sedentary control subjects of similar age and sex. Mitral, tricuspid, aortic and pulmonic regurgitations were sought in all possible views and mitral and tricuspid flow velocities were recorded. Mitral and tricuspid anulus diameters and the maximal areas of regurgitant flow were planimetered. Regurgitation of at least one of the cardiac valves was found in 91% of athletes but in only 38% of control subjects (p less than 0.001). Mitral and tricuspid regurgitation occurred more commonly in athletes than in control subjects (mitral 69 vs 27%; tricuspid 76 vs 15%). The prevalence of aortic and pulmonic regurgitation was similar. Although athletes and sedentary normal subjects differed with respect to heart rate, right and left ventricular filling patterns and tricuspid and mitral anulus diameters, none of these variables was related to the presence or severity of regurgitation. Thus, exercise training is associated with an increased prevalence of mitral and tricuspid regurgitation and altered ventricular inflow patterns. The mechanism of these findings is unclear. Multivalvular regurgitation is common in athletes and does not imply structural valvular abnormalities.

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.

Endurance exercise in the presence of heart disease.

Although patients with heart disease have successfully completed marathon runs, the immediate cardiac effects of similar and greater distance endurance exercise competition are unknown. Two such cases are presented, demonstrating that vigorous exercise and extreme levels of fitness are not precluded in the cardiac patient.

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.

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)

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.

Training for ultraendurance triathlons.

There are wide individual variations in training distances and paces for each of the three activities involved in a triathlon. Peak weekly swim distances ranged from 1 to 20 miles, with an average weekly distance of 7.2 miles. Usual swim training pace varied from 17 to 50 min.mile-1, with an average swim training pace of 29.6 min.mile-1. Peak weekly cycling distances ranged from 15 to 435 miles; average was 227 miles. Cycling pace averaged 18.6 mph and ranged from 13 to 26 mph. Run distances ranged from 4 to 100 miles.wk-1 at paces between 5 1/2 and 14 min.mile-1. Average run training was 45 miles.wk-1 at a 7 min 42 s pace. There was little or no systematic difference in training between males and females. Younger triathletes, however, tended to train greater distances at faster paces. Faster finishers (less than 10.5 h in the Hawaii Ironman Triathlon) tended to average greater training distances at faster paces than slower finishers. There was, however, a great deal of overlap in training practices according to finish time. Faster finishers in the Hawaii Ironman Triathlon were able to maintain their training paces throughout all three activities of the triathlon. Large differences were seen between faster finishers and slower finishers, particularly in the ability to hold run training pace during the race. The reason for this remains unclear. Training distances appear to be more important than training paces in preparation for an ultraendurance triathlon.

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.

The ultraendurance triathlete: a physiological profile.

To better characterize the athletes who participate in ultraendurance triathlons, 14 triathletes in training for the Hawaii IRONMAN triathlon were studied. A physical and physiological profile was developed from anthropometric measurements and oxygen uptake during maximal exercise on a treadmill, cycle ergometer, and arm ergometer. A comparison of the maximal values among exercise modes and between males and females was made. A comparison of height, weight, and percent body fat of these triathletes with elite athletes from the sports of swimming, cycling, and running showed the physique of triathletes to be most similar to that of cyclists. Oxygen uptake at maximal exercise was, for males and females, respectively: 68.8 ml X kg-1 X min-1, 65.9 ml X kg-1 X min-1 on the treadmill; 66.7 ml X kg-1 X min-1, 61.6 ml X kg-1 X min-1 on the cycle ergometer; and 49.1 ml X kg-1 X min-1, 39.7 ml X kg-1 X min-1 on the arm ergometer. When comparing the highest oxygen uptake attained at maximal exercise in any one of the three exercise modes, the male triathletes are comparable to swimmers, but have a lower aerobic capacity than cyclists or distance runners. The female triathletes studied were able to attain oxygen uptake values greater than those previously reported for female athletes.

Hemolysis during triathlon races: its relation to race distance.

Ninety-five triathletes were evaluated for evidence of hemolysis during triathlon races of two different distances. Thirty competitors (11 males, 19 females) were studied before and after the United States Triathlon Series (USTS) National Championship Race (1.5K swim, 40K bike, and 10K run). Pre- and post-race venous blood samples showed that 93% of the USTS athletes had decreased serum haptoglobin, post-race (mean decrease = 20%). Seven of 30 of the USTS triathletes (3 males, 4 females) were found to have occult blood in their urine, post-race. Only two of the USTS triathletes (1 male, 1 female) were anemic as judged by pre-race hemoglobin levels. Similar data were collected on 65 triatheletes (46 males, 19 females) at the Hawaii IRONMAN Triathlon World Championship (3.9K swim, 180.2K bike, and 42.2K run). Pre- and post-race venous blood samples showed that 95% of the IRONMAN athletes had decreases in serum haptoglobin, post-race (mean decrease = 32%). Occult blood was found in the post-race urine of 19 (12 males, 7 females) of the IRONMAN competitors. Nineteen IRONMAN triathletes (18 males, 1 female) were judged to be anemic from pre-race hemoglobin measurements. Data from two different length triathlons suggest that nearly all triathletes break down red blood cells during a race, and that the extent of the hemolysis is related to race distance.

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)

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.

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.

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.

Overuse injuries in ultraendurance triathletes.

Overuse injuries represent the largest percentage of sports-related injuries requiring medical treatment. These injuries represent a substantial health issue for the millions of adults who have made physical activity an integral part of their lifestyle, but may be even more important to those pursuing ultraendurance exercise. The purposes of this study were to report the type and incidence of overuse injuries in ultraendurance triathletes and to relate training practices to injury occurrence. Data was gathered from the responses of 95 competitors (75 men, 20 women) in the 1986 Hawaii Ironman Triathlon who completed a training and medical history questionnaire. In this sample, virtually all (91%) sustained at least one soft tissue, overuse injury during the previous year's training. The area of the body most frequently involved was the back, but the most common pattern was to have multiple areas involved. Because of the consistent combinations of injuries, mechanical abnormalities, such as diminished shock absorption, may have contributed to injury. Training habits were extremely variable and not directly related to either the incidence or type of injury.

Medical and physiological considerations in triathlons.

Triathlons (races involving consecutive swimming, bicycling, and running) have become commonplace in the United States. These races may involve from 30 minutes to 36 hours of continuous exercise, usually in warm or hot environments. Little has been published regarding the medical and physiological aspects of these events. This paper represents the first large study to date on the subject, including both an analysis of medical complications at six triathlons as well as a prospective electrolyte study conducted at two of these races. Medical records were kept and examined for all athletes requiring treatment during a typical United States Triathlon Series (USTS) race in 1986 (1,000 starters; finish times, 2 to 4 hours), a typical Ironman Qualifier (IQ) race in 1986 (622 starters; finish times, 4 to 8 hours), and the 1982 through 1985 Hawaii Ironman World Championships (4,583 starters; finish times, 9 to 17 hours). At the USTS race, fewer than 2% (17/1,000) of the starters required aid, at the IQ, approximately 10% (61/622) of the starters were treated, and at the Ironman, an average of 17% (794/4,583) received medical attention. The most common diagnoses at the USTS and IQ were dehydration and heat exhaustion. At the Ironman, dehydration and heat problems were complicated by hyponatremia. Because hyponatremia has been reported as a complication of ultraendurance events, a prospective study was performed on 36 athletes during a USTS race and 64 athletes at the 1984 Ironman race. Prerace and postrace blood samples showed that no athletes were hyponatremic following the shorter USTS race, but 27% (17/64) of the athletes studied were hyponatremic following the Ironman race.(ABSTRACT TRUNCATED AT 250 WORDS)

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.