Dietary and performance assessment of elite soccer players during a period of intense training.

This study examined the nutritional and performance status of elite soccer players during intense training. Eight male players (age 17+/-2 years) of the Puerto Rican Olympic Team recorded daily activities and food intake over 12 days. Daily energy expenditure was 3,833+/-571 (SD) kcal, and energy intake was 3,952+/-1,071 kcal, of which 53.2+/-6.2% (8.3 g x kg BW(-1)) was from carbohydrates (CHO), 32.4+/-4.0% from fat, and 14.4+/-2.3% from protein. With the exception of calcium, all micronutrients examined were in accordance with dietary guidelines. Body fat was 7.6+/-1.1% of body weight. Time to completion of three runs of the soccer-specific test was 37.65+/-0.62 s, and peak torques of the knee flexors and extensors at 60 degrees x s(-1) were 139+/-6 and 225+/-9 N x m, respectively. Players' absolute amounts of CHO seemed to be above the minimum recommended intake to maximize glycogen storage, but calcium intakes were below recommended. Their body fat was unremarkable, and they had a comparatively good capacity to endure repeated bouts of intense soccer-specific exercise and to exert force with their knee extensors and flexors.

Bone density and cyclic ovarian function in trained runners and active controls.

This study was conducted to determine whether rigorous exercise training adversely affects ovarian hormone levels and bone health in cyclically menstruating trained runners. Ovarian hormones, bone mineral density (BMD), body composition, 3-d diet records, 3-d estimated energy expenditure, and menstrual histories were evaluated in 10 trained collegiate runners and 10 moderately active controls. The trained runners had lower total body calcium per kg of soft lean tissue measured by DEXA (P = 0.045). Half of the trained runners had experienced stress fractures compared with only one of the moderately active controls. The trained runners' lumbar (L2-L4) BMD (1.178 g.cm-2) was not significantly different from that of the active controls (1.283 g.cm-2) (P = 0.074) but, for all subjects combined, there wasa significant inverse relation between L2-L4 BMD and distance run per week (P = 0.036). Further, adding age, body weight, percent body fat, daily energy intake, and daily calcium intake to a stepwise multiple regression analysis did not significantly improve predictive precision. The trained runners consumed nearly twice the amount of calcium (1089 mg.d-1 vs 641 mg.d-1, respectively; P = 0.036), while intake of other nutrients did not differ significantly between groups. Urinary estrone conjugates (E1C) were lower in the trained runners during the early follicular phase (P = 0.028), while pregnanediol-3-glucuronide (PdG) was not significantly different between groups during the luteal phase (P = 0.213). Thus, it appears that lower estrogen production, especially during the early follicular phase, and not progesterone, is associated with lower whole body calcium per kg of soft lean tissue and, probably, L2-L4 BMD. Results of this study also suggest that regular menstrual cycles do not imply normal ovarian hormone function in young women who are engaged in either recreational or competitive running.

Effects of hyperhydration on total body water, temperature regulation and performance of elite young soccer players in a warm climate.

The purpose of this study was to test the effect of increased fluid intake on temperature regulation and performance in elite soccer players. Eight players of the Puerto Rico National Team were studied under field conditions at a Wet Bulb Globe Temperature (WBGT) heat stress index of 25.3 +/- 0.5 degrees C. They were young (17.0 +/- 0.6 yr) and well aerobically conditioned, as shown by their maximum aerobic power of 69.2 +/- 0.7 ml.kg(-1).min(-1). Players were randomly allocated to a week of voluntary hydration (VH) (fluid intake = 2.7 +/- 0.2.day(-1)) and a week of hyperhydration (HH) (fluid intake = 4.6 +/- 0.2.day(-1)) (p <0.05) prior to a soccer match. Their total body water (TBW) increased in HH compared to VH (p<0.05), despite a significant increase in urine output (p < 0.01). The soccer match was played at 82 +/- 7% (VH) and 83 +/- 6% (HH) of maximum heart rate. Sweat losses and core temperature increases during the match were similar in both hydration conditions. When the environmental conditions were taken into consideration, the increase in core temperature during the match rose, as a function of the heat stress index, only in VH (p < 0.05). Plasma volume was slightly reduced in both hydration conditions (ns). Performance assessment at the end of the soccer match revealed that average time to complete 7 repetitions of a soccer specific test was significantly increased (p < 0.05) after the match in both hydration conditions but showed no difference between them. Peak torque and fatigability of knee flexor and extensor muscle groups at 240 deg.sec(-1), measured on a Cybex 340 dynamometer were similar in both hydration conditions and not affected by the soccer match. The data suggest that additional water intake in these heat-acclimated players increased body water reserves and improved temperature regulation during a soccer match with no significant effect on the decrement in soccer specific performance observed at the end of a soccer match.

Energy expenditure in lactating women: a comparison of doubly labeled water and heart-rate-monitoring methods.

Estimates of total daily energy expenditure (TDEE) by heart-rate (HR) monitoring were compared with those made by the doubly labeled water (DLW) method in nine exclusively breast-feeding women. Subjects recorded HR and dietary intake daily during the 8-d, isotope-measurement period. Milk energy output was determined by 3-d test weighing and analysis of 24-h milk samples. Total energy output (milk energy and TDEE) averaged 12.36 +/- 1.03 MJ/d with DLW compared with 11.74 +/- 1.3 MJ/d with HR monitoring, a 5.8% difference (NS). Individual differences ranged from -27.1% to +17.6%. The high water turnover and relatively low level of activity during lactation made the slopes of deuterium and 18O disappearance more similar, resulting in increased error in estimates of TDEE by DLW. Therefore, the DLW method may not be appropriate for use in lactating women. There are considerable individual deviations in estimating TDEE by HR monitoring, but it is satisfactory for estimating TDEE of groups.

Body composition in elderly men: effect of dietary modification during strength training.

OBJECTIVE: To assess how dietary change affects gain in strength and muscle mass during heavy resistance training of elderly men. DESIGN: Randomized controlled trial. INTERVENTION: During 12 weeks of resistance training of knee extensors and flexors, a daily supplement of 560 +/- 16 kcal/day (17% energy from protein, 43% from carbohydrate, 40% from fat) was randomly assigned to six men (S) while five men (U) received no supplement. Food intake, strength, whole body composition, and midthigh composition by CT scan were assessed before training and at 6 and 12 weeks. SETTING: The men were outpatients but lived in a Metabolic Research Unit during the three assessments. PARTICIPANTS: Eleven healthy men aged 61 to 72 years. RESULTS: Densitometry showed no change over time in fat or fat-free mass. However, the S men increased (P less than 0.05) weight, skinfold thickness at six sites, subcutaneous midthigh fat, and creatinine excretion; in all men, changes in these values and in midthigh muscle were proportional to changes in reported energy intake (P less than 0.05). There was midthigh muscle hypertrophy in both groups, but it was greater in S than U (P less than 0.01). Both groups gained strength (P less than 0.001) with no effect of diet. CONCLUSIONS: During physical rehabilitation of the elderly, dietary intake may influence the increase in lean as well as adipose tissue without altering strength gain. These preliminary findings should be confirmed by a larger study with sedentary controls.

Effect of suspending exercise training on resting metabolic rate in women.

We tested the hypothesis that enhanced resting metabolic rate (RMR) in highly trained endurance athletes is an acute effect of prior exercise induced by catecholamines and not serum thyroxine. RMR and energy-regulating hormones were studied in nine highly trained women runners during habitual training (period I), and suspension of training (period II). Data were collected during the follicular phase of two consecutive menstrual cycles, confirmed by serum progesterone and estradiol. Subjects maintained training between the two periods. Total energy intake and diet composition, body weight, and oral temperature did not change from period I to period II (P greater than 0.05). With suspension of training, urinary epinephrine and nonrepinephrine excretion dropped (P less than 0.022) while serum TSH rose (P = 0.011) and free T4 did not change (P = 0.182). RMR (mean +/- SEM) was 274 +/- 6.2 and 252 +/- 7.8 kJ.h-1 for periods I and II, respectively, with repeated measures ANOVA indicating a drop in RMR occurred with cessation of exercise (P = 0.048). The augmentation of RMR by exercise lasted more than 15 h but less than 39 h post-exercise. The results suggest that the drop in catecholamines may partly explain the lower RMR following suspension of training.

Plasma creatine kinase activity and exercise-induced muscle damage in older men.

Plasma creatine kinase (CK) activity has often been used as a marker of exercise-induced skeletal muscle damage. While the pattern of muscle damage following eccentric exercise has been established in young adults, there is little data available on eccentric exercise-induced muscle damage in older individuals. The purpose of this study was to compare ultrastructural changes in skeletal muscle following high intensity eccentric exercise of young and older men and to determine whether CK activity is a reliable predictor of muscle damage. Five young (20-30 yr) and five older untrained men (59-63 yr) performed three 15-min bouts of eccentric exercise at 90, 80, and 70% of maximal concentric power output. There was a prolonged increase in CK up to 10 d following exercise that was not significantly different between groups. Light and electron microscopic examination of needle biopsies obtained from the vastus lateralis showed evidence of focal damage in greater than 90% of the post-exercise fibers examined in the older subjects, compared with values ranging from 5 to 50% reported previously in young subjects. Quantitative analysis using light microscopy showed greater damage in the older subjects than reported previously in young subjects. These data suggest that older adults experience greater muscle damage following eccentric exercise than young subjects, which may be due in part to the smaller muscle mass and lower VO2max seen in older men. In addition, there was no relationship between CK activity and the corresponding amount of muscle damage observed in each subject, suggesting that CK activity may be a poor predictor of exercise-induced muscle damage.

Enhanced protein breakdown after eccentric exercise in young and older men.

The effects of eccentric exercise on whole body protein metabolism were compared in five young untrained [age 24 +/- 1 yr, maximal O2 uptake (VO2max) = 49 +/- 6 ml.kg-1.min-1] and five older untrained men (age 61 +/- 1 yr, VO2max = 34 +/- 2 ml.kg-1.min-1). They performed 45 min of eccentric exercise on a cycle ergometer at a power output equivalent to 80% VO2max (182 +/- 18 W). Beginning 5 days before exercise and continuing for at least 10 days after exercise, they consumed a eucaloric diet providing 1.5 g.kg-1.day-1 of protein. Leucine metabolism in the fed state was measured before, immediately after, and 10 days after exercise, with intravenous L-[1-13C]leucine as a tracer (0.115 mumol.kg-1.min-1). Leucine flux increased 9% immediately after exercise (P less than 0.011) and remained elevated 10 days later, with no effect of age. Leucine oxidation increased 19% immediately after exercise and remained 15% above baseline 10 days after exercise (P less than 0.0001), with no effect of age. In the young men, urinary excretion of 3-methylhistidine per gram of creatinine did not increase until 10 days postexercise (P less than 0.05), but in the older men, it increased 5 days after exercise and remained high through 10 days postexercise (P less than 0.05), averaging 37% higher than in the young men. These data suggest that eccentric exercise produces a similar increase in whole body protein breakdown in older and young men, but myofibrillar proteolysis may contribute more to whole body protein breakdown in the older group.

High-intensity strength training in nonagenarians. Effects on skeletal muscle.

Muscle dysfunction and associated mobility impairment, common among the frail elderly, increase the risk of falls, fractures, and functional dependency. We sought to characterize the muscle weakness of the very old and its reversibility through strength training. Ten frail, institutionalized volunteers aged 90 +/- 1 years undertook 8 weeks of high-intensity resistance training. Initially, quadriceps strength was correlated negatively with walking time (r = -.745). Fat-free mass (r = .732) and regional muscle mass (r = .752) were correlated positively with muscle strength. Strength gains averaged 174% +/- 31% (mean +/- SEM) in the 9 subjects who completed training. Midthigh muscle area increased 9.0% +/- 4.5%. Mean tandem gait speed improved 48% after training. We conclude that high-resistance weight training leads to significant gains in muscle strength, size, and functional mobility among frail residents of nursing homes up to 96 years of age.

Use of p-aminobenzoic acid to monitor compliance with prescribed dietary regimens during metabolic balance studies in man.

A new method is described for simultaneously monitoring compliance with prescribed-diet and urine-collection regimens during metabolic balance studies. It involves incorporation of the potassium salt of p-aminobenzoic acid (PABA) into provided foods and measurement of its extent of recovery in urine. A validation study was conducted in 10 healthy adults. During three consecutive 24-h periods, subjects consumed four foods per day that had each been supplemented with 72.0 mg PABA and also made complete urine collections. An additional 24-h urine collection was made by each subject for determination of baseline PABA excretion. The PABA was easily incorporated into the test foods and was not detected by taste. The recovery of the PABA in urine, determined by colorimetric assay, was 98.7 +/- 3.7% (means +/- SD) of intake. Thus, in metabolic studies for greater than or equal to 3 d, PABA can be used to provide a sensitive index of dietary compliance.

Strength training and determinants of VO2max in older men.

The effects of strength training on maximal aerobic power (VO2max) and some of its determinants were studied in 12 healthy older men (60-72 yr). They underwent 12 wk of strength conditioning of extensors and flexors of each knee with eight repetitions per set, three sets per session, and three sessions per week at 80% of the one repetition maximum (1 RM). Left knee extensors showed a 107% increase in 1 RM, a 10% increase in isokinetic strength at 60 degrees/s, and a 23% increase in total work performed during 25 contractions on an isokinetic dynamometer. Strength measurements of the untrained left elbow extensors showed no change. Leg cycle ergometer VO2max per unit fat-free mass increased by an average 1.9 ml (P = 0.034) whereas arm cycle VO2max was unchanged. Pulmonary function, hemoglobin concentration, erythrocyte volume, plasma volume, and total blood volume did not change. Biopsies of the vastus lateralis showed a 28% increase in mean fiber area, no change in fiber type distribution, a 15% increase in capillaries per fiber, and a 38% increase in citrate synthase activity. The data suggest that the small increase in leg cycle VO2max in older men may be due to adaptations in oxidative capacity and increased mass of the strength-trained muscles.

Peripheral effects of endurance training in young and old subjects.

The effects of 12 wk of endurance training at 70% peak O2 consumption (VO2) were studied in 10 elderly (65.1 +/- 2.9 yr) and 10 young (23.6 +/- 1.8 yr) healthy men and women. Training had no effect on weight or body composition in either group. The elderly had more adipose tissue and less muscle mass than the young. Initial peak VO2 was lower in the elderly, but the absolute increase of 5.5-6.0 ml.kg-1.min-1 after training was similar for both groups. Muscle biopsies taken at rest showed that, before training, muscle glycogen stores were 61% higher in the young. Before training, glycogen utilization per joule during submaximal exercise was higher in the elderly. Glycogen stores and muscle O2 consumption increased significantly in response to training in the elderly only. After training, the proportion of energy derived from whole body carbohydrate oxidation during submaximal exercise declined in the young only. The absolute changes that training produced in peak VO2 were similar in both age groups, but the 128% increase in muscle oxidative capacity was greater in the elderly, suggesting that peripheral factors play an important role in the response of the elderly to endurance exercise.

Dietary protein requirements and body protein metabolism in endurance-trained men.

The effects of regular submaximal exercise on dietary protein requirements, whole body protein turnover, and urinary 3-methylhistidine were determined in six young (26.8 +/- 1.2 yr) and six middle-aged (52.0 +/- 1.9 yr) endurance-trained men. They consumed 0.6, 0.9, or 1.2 g.kg-1.day-1 of high-quality protein over three separate 10-day periods, while maintaining training and constant body weight. Nitrogen measurements in diet, urine, and stool and estimated sweat and miscellaneous nitrogen losses showed that they were all in negative nitrogen balance at a protein intake of 0.6 g.kg-1.day-1. The estimated protein requirement was 0.94 +/- 0.05 g.kg-1.day-1 for the 12 men, with no effect of age. Whole body protein turnover, using [15N]glycine as a tracer, and 3-methylhistidine excretion were not different in the two groups, despite lower physical activity of the middle-aged men. Protein intake affected whole body protein flux and synthesis but not 3-methylhistidine excretion. These data show that habitual endurance exercise was associated with dietary protein needs greater than the current Recommended Dietary Allowance of 0.8 g.kg-1.day-1. However, whole body protein turnover and 3-methylhistidine excretion were not different from values reported for sedentary men.

Influence of fasting on carbohydrate and fat metabolism during rest and exercise in men.

Metabolic effects of an overnight fast (postabsorptive state, PA) or a 3.5-day fast (fasted state, F) were compared in eight healthy young men at rest and during exercise to exhaustion at 45% maximum O2 uptake. Glucose rate of appearance (Ra) and disappearance (Rd) were calculated from plasma glucose enrichment during a primed, continuous infusion of [6,6-2H]glucose. Serum substrates and insulin levels were measured and glycogen content of the vastus lateralis was determined in biopsies taken before and after exercise. At rest, whole-body glucose flux (determined by the deuterated tracer) and carbohydrate oxidation (determined from respiratory exchange ratio) were lower in F than PA, but muscle glycogen levels were similar. During exercise, glucose flux, whole-body carbohydrate oxidation, and the rate of muscle glycogen utilization were significantly lower during the fast. In the PA state, glucose Ra and Rd increased together throughout exercise. However, in the F state Ra exceeded Rd during the 1st h of exercise, causing an increase in plasma glucose to levels similar to those of the PA state. The increase in glucose flux was markedly less throughout F exercise. Lower carbohydrate utilization in the F state was accompanied by higher circulating fatty acids and ketone bodies, lower plasma insulin levels, and the maintenance of physical performance reflected by similar time to exhaustion.

Hormone and bone mineral status in endurance-trained and sedentary postmenopausal women.

Serum hormone levels and bone mineral status were studied in 18 sedentary and 15 endurance-trained postmenopausal women (mean age, 62 yr). The endurance-trained women had lower body weight, lower body fat, and higher aerobic capacity than the sedentary women (P less than 0.05). There were no differences in current calcium intake between the 2 groups, as assessed by a 7-day food record, but carbohydrate intake (grams per kg BW) was higher in the endurance-trained women (P less than 0.001). Bone mineral density (BMD) of the spine (L1-L3), proximal femur, and radius did not differ between the 2 groups; however, when normalized for body weight, the BMDs of the spine and radius were higher in the endurance-trained than in the sedentary women. Serum estrone and PTH levels were lower, and 1,25-dihydroxyvitamin D and somatomedin-C levels were higher in the endurance-trained than in the sedentary women. Serum GH tended to be higher in the endurance-trained than in the sedentary women (P = 0.08), and there was a postexercise increase in serum GH in the endurance-trained, but not in the sedentary, women (P less than 0.01). The major effect of habitual exercise was on body weight and hormone status. Although leanness and low serum estrone levels are risk factors for osteoporosis, these were not associated with lower BMD in endurance-trained women. Endurance-trained women may have improved calcium absorption as a result of higher carbohydrate intake and higher serum 1,25-dihydroxyvitamin D levels.

Strength conditioning in older men: skeletal muscle hypertrophy and improved function.

The effects of strength conditioning on skeletal muscle function and mass were determined in older men. Twelve healthy untrained volunteers (age range 60-72 yr) participated in a 12-wk strength training program (8 repetitions/set; 3 sets/day; 3 days/wk) at 80% of the one repetition maximum (1 RM) for extensors and flexors of both knee joints. They were evaluated before the program and after 6 and 12 wk of training. Weekly measurements of 1 RM showed a progressive increase in strength in extensors and flexors. By 12 wk extensor and flexor strength had increased 107.4 (P less than 0.0001) and 226.7% (P less than 0.0001), respectively. Isokinetic peak torque of extensors and flexors measured on a Cybex II dynamometer increased 10.0 and 18.5% (P less than 0.05) at 60 degrees/s and 16.7 and 14.7% (P less than 0.05) at 240 degrees/s. The torque-velocity relationship showed an upward displacement of the curve at the end of training, mainly in the slow-velocity high-torque region. Midthigh composition from computerized tomographic scans showed an increase (P less than 0.01) in total thigh area (4.8%), total muscle area (11.4%), and quadriceps area (9.3%). Biopsies of the vastus lateralis muscle revealed similar increases (P less than 0.001) in type I fiber area (33.5%) and type II fiber area (27.6%). Daily excretion of urinary 3-methyl-L-histidine increased with training (P less than 0.05) by an average 40.8%. Strength gains in older men were associated with significant muscle hypertrophy and an increase in myofibrillar protein turnover.

Body composition and aerobic capacity in young and middle-aged endurance-trained men.

Aging is associated with increased body fat, decreased muscle mass, lower maximal O2 uptake, and lower energy intake. It has been asserted that these changes are caused in part by decreased activity. In order to determine the effects of aging in men who are habitually active, 6 young men (26.8 +/- 1.2 yr) and 6 middle-aged men (52.0 +/- 1.9 yr) who had been running, cycling, and/or rowing for at least 2 yr were studied in a metabolic ward. The men consumed a diet to maintain constant body weight while keeping to their usual exercise schedule and intensity. Both groups had a similar body mass index and muscle mass, but the middle-aged men had a 77% greater fat mass (P = 0.028). Daily energy requirement was 17% lower in the middle-aged men (P = 0.029) although basal metabolic rate was similar in both groups. Aerobic capacity was 15% lower in the middle-aged men per unit body weight (P = 0.048) but not per unit of lean body mass. The young men exercised for an average 12.3 hr.wk-1 and the middle-aged men for 7.5 hr.wk-1 (P = 0.018). For both young and middle-aged men, weekly hours of exercise were negatively correlated with fat mass, and positively correlated with daily energy requirements and maximal O2 uptake. These findings show that in both young and middle-aged men who habitually exercise aerobically at 65 to 80% maximal O2 uptake, the time spent training was associated with body composition, energy requirements, and aerobic capacity.

Eccentric exercise-induced muscle damage impairs muscle glycogen repletion.

Five healthy untrained young male subjects were studied before, immediately after, and 10 days after a 45-min bout of eccentric exercise on a cycle ergometer (201 W). The subjects were sedentary at all other times and consumed a eucaloric meat-free diet. Needle biopsies of the vastus lateralis muscle were examined for intracellular damage and glycogen content. Immediately after exercise, muscle samples showed myofibrillar tearing and edema. At 10 days, there was myofibrillar necrosis, inflammatory cell infiltration, and no evidence of myofibrillar regeneration. Glycogen utilization during the exercise bout was 33 mmol glycosyl units/kg muscle, consistent with the metabolic intensity of 44% of maximal O2 uptake; however, the significant glycogen use by type II fibers contrasted with concentric exercise performed at this intensity. At 10 days after exercise, muscle glycogen was still depleted, in both type I and II fibers. It is possible that the alterations in muscle ultrastructures were related to the lack of repletion of muscle glycogen. Damage produced by eccentric exercise was more persistent than previously reported, indicating that more than 10 days may be necessary for recovery of muscle ultrastructure and carbohydrate reserves.

Metabolic changes following eccentric exercise in trained and untrained men.

The effects of one 45-min bout of high-intensity eccentric exercise (250 W) were studied in four male runners and five untrained men. Plasma creatine kinase (CK) activity in these runners was higher (P less than 0.001) than in the untrained men before exercise and peaked at 207 IU/ml 1 day after exercise, whereas in untrained men the maximum was 2,143 IU/ml 5 days after exercise. Plasma interleukin-1 (IL-1) in the trained men was also higher (P less than 0.001) than in the untrained men before exercise but did not significantly increase after exercise. In the untrained men, IL-1 was significantly elevated 3 h after exercise (P less than 0.001). In the untrained group only, 24-h urines were collected before and after exercise while the men consumed a meat-free diet. Urinary 3-methylhistidine/creatinine in the untrained group rose significantly from 127 mumol/g before exercise to 180 mumol/g 10 days after exercise. The results suggest that in untrained men eccentric exercise leads to a metabolic response indicative of delayed muscle damage. Regularly performed long distance running was associated with chronically elevated plasma IL-1 levels and serum CK activities without acute increases after an eccentric exercise bout.