Muscular characteristics of detraining in humans

Skeletal muscle is characterized by its ability to dynamically adapt to variable levels of functional demands. During periods of insufficient training stimulus, muscular detraining occurs. This may be characterized by a decreased capillary density, which could take place within 2--3 wk of inactivity. Arterial-venous oxygen difference declines if training stoppage continues beyond 3--8 wk. Rapid and progressive reductions in oxidative enzyme activities bring about a reduced mitochondrial ATP production. The above changes are related to the reduction in VO(2max) observed during long-term training cessation. These muscular characteristics remain above sedentary values in the detrained athlete but usually return to baseline values in recently trained individuals. Glycolytic enzyme activities show nonsystematic changes during periods of training cessation. Fiber distribution remains unchanged during the initial weeks of inactivity, but oxidative fibers may decrease in endurance athletes and increase in strength-trained athletes within 8 wk of training stoppage. Muscle fiber cross-sectional area declines rapidly in strength and sprint athletes, and in recently endurance-trained subjects, whereas it may increase slightly in endurance athletes. Force production declines slowly and in relation to decreased EMG activity. Strength performance in general is readily maintained for up to 4 wk of inactivity, but highly trained athletes' eccentric force and sport-specific power, and recently acquired isokinetic strength, may decline significantly.     

Cardiorespiratory and metabolic responses to exercise in HbSC sickle cell patients

PURPOSE: Relative to healthy control individuals with normal hemoglobin (Hb), patients carrying the double heterozygous form of sickle cell disease (HbSC) display an impaired oxygen transport capacity. The present study was undertaken to determine the influence of the decreased oxygen availability associated with the presence of HbSC on the cardiorespiratory and metabolic responses to endurance exercise. METHODS: Eleven black men affected by the double heterozygous form of the sickle cell disease (HbSC group) and seven healthy subjects with normal Hb (HbAA group) of the same ethnic origin submitted successively to an incremental exercise test to exhaustion on a cycle ergometer for the determination of their maximal tolerated power and to a 20-min endurance exercise. RESULTS: The HbSC had a significantly lower exercise tolerance than the HbAA. During the endurance exercise, they exhibited furthermore significantly lower VO2, VCO2, and minute ventilation V(E) than the HbAA. Despite the fact that the HbSC exercised at a significantly lower mean absolute work rate than the HbAA, except for the ventilatory equivalent for CO2 (V(E)/VCO2), which was higher (P < 0.001) in the HbSC group, the other parameters recorded during the 20-min endurance exercise (heart rate, arterial PaO2, PaCO2, pH, lactate, and VE/VO2, the ventilatory equivalent for O2) and during the subsequent recovery (blood lactate) were similar for both groups. CONCLUSION: The study underscores the importance of considering relative work rate as well as absolute work rate to arrive at a correct interpretation of exercise and recovery data. The results give evidence that the modifications of homeostasis brought into play by exercise were shifted toward distinctly lower absolute work rates in HbSC patients.     

Effects of short- and long-term detraining on the metabolic response to endurance exercise

Changes in the metabolic response to an endurance exercise were studied (18 rowing km at 75 % of maximal aerobic velocity) during detraining in ten rowers previously highly-trained. Maximal aerobic velocity (VO2 max) and the metabolic response to exercise were determined in the 1 st, 24 th, and 47 th week (training), and in the 52 nd, 76 th, and 99 th week (detraining). Over the decrease of VO2 max, detraining induced a biphasic alteration of the previously observed training adaptations: 1-short-term detraining (5 weeks) resulted in a lower adipose tissue triglyceride (TG) delivery during exercise (p = 0.029), but this one did not represent a direct metabolic limit to exercise since the liver TG delivery increased (p = 0.039), allowing that total fatty acid concentration remained unchanged (12.1 +/- 2.4 vs. 11.8 +/- 2.1 mmol/l; weeks 47 vs. 52); 2-long-term detraining (52 weeks) altered even more the metabolic response to exercise with a decreased total fatty acid concentration during exercise (week 99: 10.6 +/- 2.0 mmol/l; p = 0.022), which induced a higher glycolysis utilization. At this moment, a hemolytic response to endurance exercise was observed through haptoglobin and transferrin concentration changes (weeks 47 vs. 99; p = 0.029 and 0.027, respectively), which resulted probably from higher red blood cell destruction. Endurance-trained athletes should avoid detraining periods over a few weeks since alterations of the metabolic adaptations to training may become rapidly chronic after such delays.     

Cardiorespiratory and metabolic responses during straight and bent knee cycling

BACKGROUND: This study examined the influence of knee angle on the cardiorespiratory system loading during submaximal and maximal stationary cycle ergometry. METHODS: Experimental design and participants: eighteen untrained women (age: 21+/-1.88 years, weight: 57+/-5.75 kg, height: 165+/-5.03 cm, values are mean+/-SD) volunteered as subjects and underwent two-cycle ergometer incremental (Jaeger ER900) tests: 1) straight knee (180 degrees), 2) bent knee (140 degrees). Measures: oxygen uptake (VO2), ventilation (VE) and respiratory exchange ratio (RER) were measured continuously during each test using an open circuit spirometry and blood lactate concentration was determined by means of an enzymatic method. RESULTS: Comparing cycling with "straight knee" to cycling with "bent knee" at 50 W, heart rate (HR), V(E) and VO2 were significantly higher (10.6%, 12.5%, 17.8%). At 100 W, blood lactate was significantly lower (10.8%) while VO2 and RER was higher (5.5%, 7.1%). During maximal exercise, the total exercise time was significantly longer (11.2%) and VE, VO2 and HR were significantly higher during cycling with "straight knee" compared to cycling with "bent knee". No significant difference in peak lactate was evident between the two sitting positions. CONCLUSIONS: The results of this study indicate that cycling with bent knee requires lower oxygen uptake while pedaling with straight knee is the only way to reach VO2max during cycle testing, since the cardiorespiratory system is fully taxed.     

Metabolic characteristics of skeletal muscle during detraining from competitive swimming

After 5 months of intense training, eight male swimmers were studied during 4 wk of inactivity. Biopsy specimens from the deltoid muscle revealed that its respiratory capacity (QO2) decreased by 50% (5174 to 2559 microliter X h-1 X g-1) after 1 wk of inactivity. Subsequent weeks of detraining did not change the QO2. Although the trained swimmers' muscle phosphofructokinase and phosphorylase activities were significantly higher (P less than 0.05) than those from a group (N = 8) of untrained men, 4 wk of detraining had no effect on these enzyme activities. Mean (+/-SE) resting muscle glycogen concentrations were significantly higher (P less than 0.05) for the trained swimmers (153 +/- 3 mmol X kg-1) than for the untrained men (85 +/- 7.5 mmol X kg-1). Over the 4 wk of inactivity, the swimmers' muscle glycogen progressively decreased from 153 (+/- 3) to 93 (+/-7) mmol X kg-1. After a standard 183-m swim at 90% of the swimmer's best time for that distance, blood lactate rose from a mean of 4.2 (+/-0.8) at week 0 to 9.7 (+/-0.8) mmol X 1(-1) at week 4. These observations demonstrate dramatic changes in the metabolic characteristics of the swimmer's muscle with a 1-4-wk interruption in training.     

老年男性代谢综合征特点及与代谢相关疾病的关系

目的 探讨老年代谢综合征（MS）的特点及与代谢相关疾病关系.方法 回顾性分析我院住院及体检的军队离退休干部健康资料4601例,根据有无MS分为MS组（1656例）和对照组（2945例）,对两组MS指标及疾病进行比较.结果 本组MS的患病率为35.99%;与对照组比较,MS组体重指数、收缩压、空腹血糖、LDH-C、TG明显升高;MS组肥胖症、高血压病、糖尿病、冠心病等发病率较对照组明显升高;MS组前列腺增生患者的下尿路症状更重,上述差异都有统计学意义（P＜0.05）.结论 MS是老年人常见合并症之一,是促进老年代谢相关疾病发生、发展的原因之一.认识和管理好MS,对提高老年人生活质量有重要意义.     

Correlations of cardiorespiratory and metabolic reactions in humans with graded physical load

Bicycle ergometry tests of graded workloads were performed by 9 healthy men, aged 25 to 40 years. During the tests cardiorespiratory parameters, lactate and pyruvate concentrations, as well as lactate dehydrogenase (LDH) and NADP-dependent isocitrate dehydrogenase (ICDH) activities were measured. It was shown that the threshold of anaerobic metabolism can be measured not only by traditional methods (with respect to variations in pulmonary ventilation and venous blood lactate) but also in terms of ICDH increase as a function of the workload. Mathematical processing of the resulting data did not reveal a correlation between the total oxygen debt and lactate in blood. In contrast, a close correlation between the debt and LDH activity at the end of the test was found. These observations have demonstrated that biochemical measurements should find a wider application in evaluations of energy costs of various workloads.     

17-Iodine-123 iodoheptadecanoic acid for metabolic liver studies in humans

(17-123I)-Iodoheptadecanoic acid ([123I]HA) was used for dynamic planar scintigraphy of the liver in normal individuals (control I), in patients without liver disease but with elevated serum cholesterol and/or triglycerides (control II), and in patient groups with alcohol-induced fatty liver (PG I), fatty liver not due to alcohol (PG II), alcohol-induced liver cirrhosis (PG III), or liver cirrhosis of the posthepatitic type (PG IV). Tracer uptake and elimination time were assayed in different liver regions; mean elimination time was expressed for total liver. In control I, tracer uptake was homogeneous, and mean elimination time was 20.7 +/- 5.3 min without significant local variations. In control II, tracer uptake was reduced but homogeneous and mean elimination time was 59.4 +/- 35.8 min with some local variations. In PG I, uptake was reduced and inhomogeneous and elimination time was the same as in control I, irrespective of cholesterol and triglyceride values. In PG II, uptake was the same as in PG I but mean elimination time was 48 +/- 8.1 min with some local variations. In PG III, uptake was extremely reduced and spotty and elimination time correlated with the severity of disease from 19 to 881 min in different liver regions.     

Frequency and characteristics of metabolic disorders in patients on haemodialysis

BACKGROUND/AIM:. Metabolic syndrome and malnutrition represent metabolic abnormalities which significantly characterize patients on haemodialysis. The aim of the study was to determine the incidence and find characteristics of metabolic disbalance in patients on haemodialysis. METHODS: The study involved 124 patients on chronic haemodialysis at the Clinical Centre Kragujevac. There were analyzed demographic and anthropometric characteristics of the examined patients. Of clinical characteristics, there were determined smoking habit, time on dialysis, arterial pressure; of comorbid states there were recorded heart diseases and diabetes mellitus. Routine biochemical analyses were carried out by a standard laboratory procedure. RESULTS: Metabolic syndrome was found in 29.8% of the examined patients. The patients with metabolic syndrome were older as compared to the patients without metabolic syndrome (58.45 +/- 12.91 vs 52.25 +/- 11.63 years). The values of systolic pressure (143.88 +/- 19.75 vs 133.01 +/- 22.93 mmHg; p = 0.014), body mass index (21.2 +/- 3.71 vs 19.4 +/- 2.88 kg/m2;p = 0.001), fat body mass (19.57 +/- 8.47 vs 16.45 +/- 5.82%; p = 0.0002) and waist scope (89 +/- 12.54 vs 96 +/- 12.34 cm; p = 0.0001) were significantly higher in the patients with metabolic syndrome as compared to those without metabolic syndrome. The values of erythrocytes (3.4 +/- 0.45 vs 19 +/- 0.53 x 10(12); p = 0.04) and hemoglobin (107 +/- 15.76 vs 101 +/- 13.87 g/l; p = 0.009), glycaemia (9.5 +/- 8.15 vs 5.6 +/- 1.4 mmol/l; p = 0.04) triglycerides (2.44 +/- 1.8 vs 1.41 +/- 0.64 mmol/l; p = 0.007), HDL cholesterol (1.11 +/- 0.19 vs 0.82 +/- 0.25 mmol/l; p = 0.005) and albumins (32.5 +/- 5.6 vs 29.5 +/- 3.7 g/l; p = 0.007) were statistically higher in the patients with metabolic syndrome than in patients without disturbance. Diabetes mellitus was a significant etiological factor of renal insufficiency in the patients with metabolic syndrome (p = 0.008). CONCLUSION: In our study approximately 30% of patients on haemodialysis had pronounced metabolic syndrome. The older, more obese men with increased levels of triglycerides and glucose in the serum dominated among them. Diabetes mellitus was a leading etiological factor of renal insufficiency in these patients.     

Age and gender responses to strength training and detraining

PURPOSE: The purpose of this study was to examine the effects of age and gender on the strength response to strength training (ST) and detraining. METHODS: Eighteen young (20-30 yr) and 23 older (65-75 yr) men and women had their one-repetition maximum (1 RM) and isokinetic strength measured before and after 9 wk of unilateral knee extension ST (3 d x wk(-1)) and 31 wk of detraining. RESULTS: The young subjects demonstrated a significantly greater (P < 0.05) increase in 1 RM strength (34+/-3%; 73+/-5 vs 97+/-6 kg; P < 0.01) than the older subjects (28+/-3%; 60+/-4 vs 76+/-5 kg, P < 0.01). There were no significant differences in strength gains between men and women in either age group with 9 wk of ST or in strength losses with 31 wk of detraining. Young men and women experienced an 8+/-2% decline in 1 RM strength after 31 wk of detraining (97+/-6 vs 89+/-6 kg, P < 0.05). This decline was significantly less than the 14+/-2% decline in the older men and women (76+/-5 vs 65+/-4 kg, P < 0.05). This strength loss occurred primarily between 12 and 31 wk of detraining with a 6+/-2% and 13+/-2% decrease in the young and older subjects, respectively, during this period. DISCUSSION: These results demonstrate that changes in 1 RM strength in response to both ST and detraining are affected by age. However, ST-induced increases in muscular strength appear to be maintained equally well in young and older men and women during 12 wk of detraining and are maintained above baseline levels even after 31 wk of detraining in young men, young women, and older men.     

Cardiorespiratory exercise training in children

Definitive statements concerning the cardiorespiratory effects of exercise training in children cannot be made. Few carefully controlled and well-defined exercise training studies including important cardiorespiratory variables have been conducted. Generally, it appears that the response to training in pubescent and postpubescent children is not different from what is observed in adults.     

Thermal and metabolic responses of sleep deprivation of humans during acute cold exposure

PURPOSE: This investigation evaluated the effects of 33 h of sleep deprivation on the thermoregulation in 12 male and female subjects (26.6 +/- 6.4 yrs) during 180 min of cold exposure in 12 degrees C air. METHODS: Subjects underwent two cold air trials (CAT): one following a normal night of sleep (i.e., 6-8 h) (CON); and one following 33 h of sleep deprivation (SDEP). Rectal temperature (Tre), mean skin temperature (Tsk), heat production (HP), and tissue insulation (Iti), were measured at 5, 15, 30, and every 30 min thereafter. RESULTS: ANOVA revealed no significant differences (p > 0.05) between CON and SDEP for Tre, Tsk, HP, and Iti. A main effect for time was demonstrated for Tre, Iti, HP, and Tsk. A trial x time interaction for Tre and Tsk (p = 0.021) was demonstrated. DISCUSSION: Significant interactions were demonstrated for Tre and Tsk, but post hoc analysis determined no differences between SDEP and CON. This may have been due to the length of the sleep deprivation, cold stressor, or a combination of the two. There were also no overall differences in HP or Iti between SDEP and CON. Further research in this area is needed to evaluate the effects of sleep deprivation during acute cold exposure.     

Cardiorespiratory fitness and stroke mortality in men

PURPOSE: We examined the association between cardiorespiratory fitness and stroke mortality in men. METHODS: This is a prospective cohort study. We followed 16,878 men, ages 40-87 yr, who had a complete medical evaluation including a maximal treadmill exercise test and self-reported health habits. There were 32 stroke deaths during an average of 10 yr of follow-up (167,961 man-yr). RESULTS: After adjustment for age and examination year, there was an inverse association between cardiorespiratory fitness and stroke mortality (P = 0.005 for trend). This association remained after further adjustment for cigarette smoking, alcohol intake, body mass index, hypertension, diabetes mellitus, and parental history of coronary heart disease (P = 0.02 for trend). High-fit men (most fit 40%) had 68% (95% CI: 0.12, 0.82) and moderate-fit men had 63% (95% CI: 0.17, 0.83) lower risk of stroke mortality when compared with low-fit men (least fit 20%), respectively. CONCLUSIONS: Moderate and high levels of cardiorespiratory fitness were associated with lower risk of stroke mortality in men in the Aerobics Center Longitudinal study population.     

Aquatic training and detraining on fitness and quality of life in fibromyalgia

PURPOSE: To evaluate the effects of a 12-wk period of aquatic training and subsequent detraining on health-related quality of life (HRQOL) and physical fitness in females with fibromyalgia. METHODS: Thirty-four females with fibromyalgia were randomly assigned into two groups: an exercise group, who exercised for 60 min in warm water, three times a week (N = 17); and a control group, who continued their habitual leisure-time activities (N = 17). HRQOL was assessed using the Short Form 36 questionnaire and the Fibromyalgia Impact Questionnaire. Physical fitness was measured using the following tests: Canadian Aerobic Fitness, hand grip dynamometry, 10-m walking, 10-step stair climbing, and blind one-leg stance. Outcomes were measured at baseline, after treatment, and after 3 months of detraining. RESULTS: After 12 wk of aquatic exercise, significant positive effects of aquatic training were found in physical function, body pain, general health perception, vitality, social function, role emotional problems and mental health, balance, and stair climbing. After the detraining period, only the improvements in body pain and role emotional problems were maintained. CONCLUSION: The present water exercise protocol improved some components of HRQOL, balance, and stair climbing in females with fibromyalgia, but regular exercise and higher intensities may be required to preserve most of these gains.     

Cardiorespiratory fitness and training in quadriplegics and paraplegics

With the growing interest in exercise and sport and the significance of cardiovascular disease in the spinal cord injured population, the role of endurance training in improving cardiovascular health is of particular interest. Ordinary daily activities of those with spinal cord injury are usually not adequate to maintain cardiovascular fitness, and lack of participation in a regular activity programme may result in a debilitative cycle. As this occurs, there is a reduction in functional work capacity which may limit independence, and the reduction in cardiovascular fitness may increase the risk for cardiovascular disease. Work capacity in those with spinal cord injury is limited by loss of functional muscle mass and sympathetic control. Sympathetic nervous system impairment limits control of regional blood flow and cardiac output, and maximum heart rate following cervical lesions may be reduced to 110 to 130 beats/min. However, endurance training in quadriplegics and paraplegics can elicit improvements in exercise performance similar to those observed in able-bodied individuals. Review of 13 cardiorespiratory training studies involving spinal cord injured subjects revealed average improvements of 20% in VO2max and 40% in physical work capacity after 4 to 20 weeks of training. Based upon the positive results of these studies, the general endurance training guidelines for the normal population appear to also be appropriate for the spinal cord injured population. These guidelines can be followed during participation in a number of different activities and sports including wheelchair pushing, arm crank ergometry, aerobic swimming, ambulation training, canoeing and wheelchair basketball. There is no evidence that intense training and competition is harmful, but special areas of risk as a result of impairments in sensation, cardiovascular function, autonomic function and temperature regulation must be considered. The long term benefits of endurance training in those with spinal cord injury has not been adequately studied, but there is suggestion that similar physiological and psychological changes may occur as in able-bodied individuals.     

Oxidative stress responses in older men during endurance training and detraining

PURPOSE: Aging is associated with increased oxidative stress, whereas systematic exercise training has been shown to improve quality of life and functional performance of the aged. This study aimed to evaluate responses of selected markers of oxidative stress and antioxidant status in inactive older men during endurance training and detraining. METHODS: Nineteen older men (65-78 yr) were randomly assigned into either a control (C, N = 8) or an endurance-training (ET, N = 11, three training sessions per week, 16 wk, walking/jogging at 50-80% of HR(max)) group. Before, immediately posttraining, and after 4 months of detraining, subjects performed a progressive diagnostic treadmill test to exhaustion (GXT). Plasma samples, collected before and immediately post-GXT, were analyzed for malondialdehyde (MDA) and 3-nitrotyrosine (3-NT) levels, total antioxidant capacity (TAC), and glutathione peroxidase activity (GPX). RESULTS: ET caused a 40% increase in running time and a 20% increase in maximal oxygen consumption (VO(2max)) (P < 0.05). ET lowered MDA (9% at rest, P < 0.01; and 16% postexercise, P < 0.05) and 3-NT levels (20% postexercise, P < 0.05), whereas it increased TAC (6% at rest, P < 0.01; and 14% postexercise, P < 0.05) and GPX (12% postexercise, P < 0.05). However, detraining abolished these adaptations. CONCLUSIONS: ET may attenuate basal and exercise-induced lipid peroxidation and increase protection against oxidative stress by increasing TAC and GPX activity. However, training cessation may reverse these training-induced adaptations.     

Cross transfer effects of muscular endurance during training and detraining

BACKGROUND: To clarify 1) how the cross-transfer effect, obtained in a contralateral untrained forearm through a 4-week ipsilateral endurance training regimen, is changed during detraining; and 2) how blood flow to the untrained limb is related to the transfer effect of muscular endurance during training and detraining periods. METHODS: Training regimen: hand-grip training by means of a hand-ergometer with a work-load of 1/3 of the maximum handgrip strength 5 times a week for 4 weeks. Blood flow: a mercury-in-rubber strain-gauge for venous occlusion plethysmography. Measures: 1) maximal number of contractions to determine the muscular endurance; 2) reactive hyperaemic blood flow response (RHBF3) to determine whether maximal vasodilatory capacity would be changed in both the forearms post-training and detraining; and 3) maximal work-related blood flow. RESULTS: We found significant increments both in the muscle endurance and the maximal work-related blood flow not only in the trained (+125%, +30%) but also in the untrained (+40%, +19%) forearms. During detraining, we found decreases both in the muscle endurance and the maximal work-related blood flow (-22%, p<0.01; -16%, p=0.053) of the trained forearm. However, in the untrained arm (-3%, NS) the cross-transfer effect of muscular endurance remained unchanged despite a drop in the maximal work-related blood flow (-17%, p<0.05). The RHBF3 did not change in either of the forearms during the whole periods. CONCLUSIONS: These findings suggest that the maintenance of the cross transfer effect of muscle endurance during detraining cannot be explained on the basis of changes in forearm blood flow.     

Cardiorespiratory fitness of finnish adolescents

We evaluated the accuracy of a submaximal cycle ergometer test to assess cardiorespiratory fitness in adolescents and provided population-based reference values. In a health study of the Northern Finland birth cohort born in 1985 - 1986 (NFBC 1986), cardiorespiratory fitness of 5375 males and females aged 15 to 16 years was measured by a submaximal cycle ergometer test by using a two-stage exercise protocol designed for this survey. A total of 4903 subjects performed two work stages. Maximal workload and peak oxygen consumption were calculated on the basis of heart rate responses by the WHO extrapolation method. An additional 472 subjects were able to finish only one work stage. For them, peak oxygen uptake was calculated by the Astrand nomogram. To evaluate the accuracy of submaximal testing, a validation sample of 90 subjects carried out both a submaximal test and a maximal cycle ergometer test with direct measurement of peak oxygen uptake. The WHO method proved to estimate peak oxygen uptake with reasonable accuracy. The Astrand nomogram method overestimated peak oxygen uptake considerably, and therefore a new single-stage regression method was applied to calculate maximal workload and peak oxygen consumption. Reference values of cardiorespiratory fitness were provided for 2690 males and 2685 females aged 15 to 16 years.     

Physiological and metabolic characteristics of elite tug of war athletes

OBJECTIVE: To determine the aerobic power (VO(2)MAX), body composition, strength, muscular power, flexibility, and biochemical profile of an elite international squad of tug of war athletes. METHODS: Sixteen male competitors (mean (SEM) age 34 (2) years) were evaluated in a laboratory. For comparative purposes, data were analysed relative to normative data for our centre and to a group of 20 rugby forwards from the Irish international squad. RESULTS: The tug of war participants were lighter (83.6 (3.0) v 104.4 (1.8) kg, p<0.0001) and had less lean body mass (69.4 (2.1) v 86.2 (1.2) kg) than the rugby players and had lower than normal body fat (16.7 (0.9)%); all values are mean (SEM). Aerobic power measured during a treadmill test was 55.8 (1.6) ml/kg/min for the tug of war participants compared with 51.1 (1.4) ml/kg/min for the rugby forwards (p<0.03). A composite measure of strength derived from (sum of dominant and non-dominant grip strength and back strength)/lean body mass yielded a strength/mass ratio that was 32% greater (p<0.0001) for the tug of war group than the rugby group. Dynamic leg power was lower for the tug of war group than the rugby forwards (4659.8 (151.6) v 6198.2 (105) W respectively; p<0.0001). Leg flexibility was 25.4 (2.0) cm for the tug of war group. Back flexibility was 28.6 (1.4) cm which was lower (p<0.02) than the rugby forwards 34.2 (1.5) cm. Whereas blood chemistry and haematology were normal, packed cell volume, haemoglobin concentration, and erythrocyte volume were lower in the tug of war group than in the rugby players (p<0.05). All three haematological measures correlated with muscle mass (packed cell volume, r(2) = 0.37, p<0.0001; haemoglobin concentration, r(2) = 0.13, p<0.05; erythrocyte volume, r(2) = 0.21, p<0.01). CONCLUSIONS: The data indicate that international level tug of war participants have excellent strength and above average endurance relative to body size, but have relatively low explosive leg power and back flexibility. The data provide reference standards for the sport and may be useful for monitoring and evaluating current and future participants.