Aerobic glycolytic and aerobic lipolytic power systems. A new paradigm with implications for endurance and ultraendurance events.
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Adenosine Triphosphate↗
Biomedical subjects
W G Hopkins
Publications and source records attributed to W G Hopkins.
Combining event scores to estimate the ability of competitors.
Simulation was used to investigate the validities of nine measures of ability derived from scores of two or more competitive events. The measures were: raw means and least-squares means of raw scores, z scores, and normal scores; two measures derived from ranked scores; and the "personal-best" raw score. Simulations were performed for different numbers of competitors, events, and event entries, each for a range of validity of performance in a single event. A complete set of simulations was repeated for each of the following conditions: normal distribution of competitors' ability; skewed distribution of ability; event validity related to ability; validity, ability, and spread of scores differing between events; and events differing in difficulty. The raw mean of raw scores was generally the most valid measure. The personal best was comparable to the mean only when the number of entries approached one per competitor. The least-squares mean of raw scores had highest validity when events differed substantially in difficulty; it should therefore be used when events differ in length, or when event scores are affected by environmental conditions, judging bias, or by uneven matching of competitors in match-play sports.
Competitive Behavior↗
Respiratory responses of elite oarsmen, former oarsmen, and highly trained non-rowers during rowing, cycling and running.
The position of the body and use of the respiratory muscles in the act of rowing may limit ventilation and thereby reduce maximal aerobic power relative to that achieved in cycling or running, in spite of the greater muscle mass involved in rowing. This hypothesis was investigated for three groups of male subjects: nine elite senior oarsmen, eight former senior oarsmen and eight highly trained athletes unskilled in rowing. The subjects performed graded exercise to maximal effort on a rowing ergometer, cycle ergometer and treadmill while respiratory minute volume (VE) and oxygen consumption (VO2) were monitored continuously. The VE at a given VO2 during intense submaximal exercise (greater than 75% of maximal VO2) was not significantly lower in rowing compared with that in cycling and treadmill running for any group, which would suggest that submaximal rowing does not restrict ventilation. At maximal effort, VO2, and VE for rowing were less than those for the other types of exercise in all the groups, although the differences were not statistically significant in the elite oarsmen. These data are consistent with a ventilatory limitation to maximal performance in rowing that may have been partly overcome by training in the elite oarsmen. Alternatively, a lower maximal VE in rowing might have been an effect rather than a cause of a lower maximal VO2, if maximal VO2 was limited by the lower rate of muscle activation in rowing.
Adult↗
Chelation therapy for intermittent claudication. A double-blind, randomized, controlled trial.
BACKGROUND: The use of repeated intravenous infusions of EDTA, which has become known as "chelation therapy," has been promoted for treating intermittent claudication as well as a wide range of other disorders. Multiple reports of excellent results in large numbers of patients have encouraged the use of this regimen. The lack of well-controlled studies substantiating the benefits of this treatment has limited its use mainly to private clinics. The aim of the study was to assess the benefits of chelation therapy in patients with intermittent claudication. METHODS AND RESULTS: A double-blind, randomized, controlled trial included 32 patients with intermittent claudication who were randomized to a treatment group (15) and a control group (17). Main outcome measures were subjective and measured walking distances and ankle/brachial pulse indices. Other outcome measures included lifestyle and subjective parameters of improvement, cardiac function, ECG, renal function, hematology, blood glucose, and lipid biochemistry. No clinically significant differences in main outcome measures between chelation therapy and placebo groups were detected up to 3 months after treatment. Measures of mood state, activities of daily living, and quality of life factors were not consistently affected by chelation therapy. An equal proportion (13%) of each group thought that they had received the active agent. The proportion of patients showing an improvement in walking distance was not significantly different between the chelation group (60%) and the control group (59%). CONCLUSIONS: Chelation therapy has no significant beneficial effects over placebo in patients with intermittent claudication.
Activities of Daily Living↗
Lifestyle advice to pregnant patients.
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Alcohol Drinking↗
Blood glucose following training sessions in runners.
The possibility that blood glucose reaches potentially dangerous concentrations following training sessions was investigated in 10 competitive runners. Blood glucose concentration was assayed in the first 60 min following a continuous run at moderate pace for 45 min, a continuous run at hard pace for 30 min, an interval training session for 15 min, and an incremental exercise test to maximum effort. Glucose concentration increased and remained high for up to 30 min following the hard-pace, interval and maximum-effort runs; maximum concentrations (mean +/- SD 6.8 +/- 1.1, 6.8 +/- 1.0, 7.8 +/- 1.1 mmol.l-1 respectively) were significantly higher (p < 0.05) than those of the moderate-pace run (4.9 +/- 0.4 mmol.l-1). A 10-min warm-down at moderate pace dramatically attenuated the surge in glucose concentration following 30 min of hard-pace running, but a pre-exercise carbohydrate snack had no effect. Level of glycation of haemoglobin in a venous blood sample (mean +/- SD 4.6 +/- 0.7 %) was normal. Thus transient elevations in blood glucose concentration following high-intensity training sessions are unlikely to damage body proteins.
Adult↗
Predictors of attainment in rhythmic sportive gymnastics.
Correlates of attainment in rhythmic sportive gymnastics (RSG) were investigated in a cross-sectional study of 106 female gymnasts aged 7-27 years. Physical attributes were obtained by anthropometry and from tests of flexibility, leg power, maximum oxygen uptake and visuo-motor proficiency. Training and psychological measures were derived from self-administered questionnaires that included the Leadership Scale for Sport, Psychological Skills Inventory for Sport, General Health Questionnaire, Sport Competition Anxiety Test, and several questions on sport motivation and enjoyment. Attainment was expressed as competition grade level and mean performance score in 4 competitions. The best correlates of attainment were cumulative and current training time (r = 0.84-0.53). Age, lean body mass and composite measures of flexibility, leg power and visuo-motor proficiency were also significant correlates of attainment (r = 0.69-0.29), as were coach democratic and coach social behaviours (r = 0.41-0.28). The significant positive psychometric correlates of attainment were mental preparation, motivation by creativity, and several dimensions of enjoyment (r = 0.35-0.26); significant negative correlates were recent anxiety-depression and enjoyment of training (r = -0.34-(-)0.32). No previous study has identified the relative contributions of such a comprehensive range of physical, psychological and training measures to performance of a sport.
Adolescent↗
Validation of subjective measures of fatigue after elective operations.
OBJECTIVE: To find out if it was possible to evaluate postoperative fatigue by questionnaire. DESIGN: Open study. SETTING: University hospital. SUBJECTS: 23 patients about to undergo elective general surgical operations. INTERVENTIONS: A questionnaire was filled in before, and 2-46 days after, operation. MAIN OUTCOME MEASURES: Six measures of fatigue were derived from the questionnaire and validated objectively with changes in body weight, exercise tolerance (n = 10), or grip strength (n = 21). RESULTS: The six measures all showed a significant increase after operation. The changes in fatigue correlated well, but there were differences in sensitivity to changes in perceived weakness compared with perceived tiredness. Each measure correlated significantly with either body weight, exercise tolerance or grip strength. CONCLUSION: Questionnaires can provide reliable results in the assessment of postoperative fatigue.
Adult↗
Lifestyle behaviours during pregnancy.
Lifestyle behaviours of 183 women before and during pregnancy were investigated by retrospective questionnaire in the first few days postpartum. The threshold of cigarette smoking for a reduction in birth weight was exceeded at full term by 17% of the women, but only 1% exceeded a similar threshold for alcohol consumption. Consumption below the recommended minimum level for one or more major food groups was reported by 35% of the women during pregnancy. Only 36% of the women were vigorously active before pregnancy, and only 13% remained so throughout pregnancy. Level of education was a significant predictor of healthy lifestyle behaviours. Concern for their baby's and their own health were the main reasons given for change in behaviour during pregnancy, while doctor's advice and antenatal classes were cited infrequently. A new approach to lifestyle enhancement by health professionals might promote desirable changes in relation to smoking and possibly also food consumption and physical activity.
Adult↗
The intensity of exercise in deep-water running.
The intensity of exercise during 30-min sessions of continuous deep-water running at a "hard" pace was determined by monitoring oxygen consumption (VO2), respiratory quotient (RQ), heart rate, perceived physical effort and perceived aches and pains in the legs in eight competitive runners, six of whom had not previously practised the technique. The intensity was compared with that of 30-min runs on a treadmill at hard and "normal" training paces and a 30-min outdoor run at normal training pace. VO2 during the last session of deep-water running (73% of maximum VO2) was not significantly different from that of the treadmill hard run (78%), but was significantly higher than that of the treadmill normal run (62%). Similar results were obtained for RQ, perceived effort and pain. In contrast, heart rates for deep-water running were similar to those of normal training and significantly less than those of the treadmill hard run. The disparity between VO2 and heart rate for deep-water running may reflect cooling or increased venous return caused by water immersion. It is concluded that deep-water running can be performed at a sufficient intensity for a sufficient period to make it an effective endurance training technique.
Adolescent↗
Validation of the physical activity instrument for the Life in New Zealand national survey.
A physical activity recall instrument suitable for self-administration by the adult New Zealand population was devised and validated for 140 subjects selected randomly from urban electoral rolls. Validation used bootstrapping to compare correlations between subjective measures derived from the instrument, the Stanford 7-day recall questionnaire and other questionnaires, and objective measures derived from an exercise test. Subjective measures were grouped as measures of high intensity activity, low intensity activity, or total activity metabolism. The high intensity measures correlated moderately with each other (mean r = 0.39), but poorly with metabolism and low intensity measures (r = 0.16, -0.02, respectively). The mean correlation between the metabolism and low intensity groups (r = 0.26) was similar to those within these groups (r = 0.31, 0.25, respectively). Thus, the high intensity measures formed a group distinct from the metabolism and low intensity groups, which represented similar measures. The objective measures that correlated with high intensity measures (mean r = 0.25) are predominantly recognized risk factors for cardiovascular disease; these did not correlate with the metabolism or low intensity measures (mean r = 0.03, -0.07, respectively). Activity measures from the instrument had mean correlations with subjective and objective measures that equaled or surpassed those of the Stanford measures from the same group. The authors conclude that 1) population health studies that assay physical activity should include well-defined measures of high intensity activity, and 2) valid measures of physical activity in the New Zealand population are achievable with this instrument.
Adolescent↗
Quantification of training in competitive sports. Methods and applications.
The training of competitive athletes can be assessed by retrospective questionnaires, diaries, physiological monitoring and direct observation of training behaviour. Questionnaires represent the most economical, most comprehensive and least accurate method. Diaries are more valid, but their drawbacks for long term quantitative studies are poor compliance and difficulties in processing the data they generate. Physiological monitoring (of oxygen consumption, heart rate or blood lactate concentration) provides objective measures of training intensity, and direct observation gives valid measures of most aspects of training; however, these methods are impractical for continuous, long term use. Coaches and athletes quantify training for purposes of motivation, systematisation of training and training prescription, but there has been little study of the use of training quantification by these practitioners. Motivation and systematisation are probably achieved best with diaries. Direct observation appears to be the best method of ensuring compliance with a training prescription, although heart rate monitoring is also a promising method for prescribing endurance training intensity. Sport scientists quantify training to study its effects on the performance and health status of competitive athletes. Most studies have been descriptive rather than experimental, and unvalidated questionnaires have been the predominant method of assaying training. The main areas of research include performance prediction and enhancement, overtraining, reproductive dysfunction, injury, illness, and nutritional status. Training has substantial effects in all of these areas. There is a need for more experimental studies that utilise validated measures of training to investigate how to reduce sports injuries and enhance competitive sports performance. More attention could also be given to methodological issues of training quantification.
Athletic Injuries↗
Training intensity of elite male distance runners.
To quantify training intensity in 13 nationally ranked male distance runners, training heart rates, environmental factors, and motivational factors were recorded throughout a 6-8 wk period of normal training. Variation in motivational and environmental factors such as intended effort, terrain, and running with companions altered training session mean heart rates by up to 4.min-1 (standard deviation). Heart rates and blood lactate concentrations, recorded in a series of steady-state treadmill runs, were used to convert training session mean heart rates to mean training speeds (TS) and to derive a measure of the anaerobic threshold (AT, the treadmill speed at a blood lactate concentration of 4 mmol.l-1). TS (15.6 +/- 1.4 km.h-1, mean +/- SD) was considerably lower than AT (20.2 +/- 1.1 km.h-1) in all subjects (P less than 0.001). Relative TS (TS expressed as a fraction of AT) differed significantly (P less than 0.001) between subjects and correlated significantly with the distance of the event for which the subject was training (r = 0.59, P less than 0.05). Relative TS may therefore be determined by the subject's or coach's perception of the appropriate intensity for the event. If the AT is the optimum training intensity, these subjects have considerable scope for improvement.
Adult↗
Competition for survival between motor units in mouse skeletal muscle.
The soleus nerve on one side of neonatal mice was crushed and the soleus muscle on the same side was surgically reduced in size. Some animals also had their lumbar spinal nerve 5 (L5) cut and misdirected in the same operation. Three months later, the number of L5 and L6 soleus motor units in the operated muscles was counted electrophysiologically and the number of muscle fibers was counted histologically. The number of L6 motor units in reduced size muscles without L5 innervation was significantly greater than it was in muscles where both L5 and L6 motor units were present. This result supports the concept that motor neuron survival during development is dependent upon the number of muscle fibers available for innervation and the number of motor neurons competing to innervate them.
Action Potentials↗
Relation between power and endurance for treadmill running of short duration.
An exercise test was devised to investigate the relationship between power and endurance for treadmill running. The subjects were 19 males aged 21-25 yr (11 distance runners and 4 sprinters of provincial grade, and 4 non-competitive runners). Each subject ran to exhaustion on a treadmill at 15 km hr-1 at five different inclinations (31%-9%), giving maximum performance times in the range 10 s to 3 min. An iterative least-squares procedure was used to fit the following exponential model to each subject's data: It = I infinity + (I0-I infinity) exp (-t/tau), where It, I0 and I infinity are inclinations at time t = t, t = 0 and t----infinity, and tau is a time constant. The fit was excellent (r2 = 0.96-1.00). I0 and I infinity are interpreted as measures of maximum anaerobic (instantaneous) and maximum aerobic (continuous) power respectively. Inclinations corresponding to performance times of 10-180 s (I10-I180) were calculated from these parameters. Test-retest reliability was highest for I0-I30 (intraclass r = 0.97-0.94), lower for I60-I infinity (r = 0.89-0.84), and lowest for tau (r = 0.78). Good correlations were observed between I0-I30 and peak power in a 30 s all-out test on a cycle ergometer (r = 0.73-0.81), and between I180, I infinity and maximum oxygen consumption (r = 0.87, 0.81). The test may be useful for ranking or monitoring running performance for events of up to 1 min duration.
Adult↗
Errors in assigning grades based on tests of finite validity.
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Educational Measurement↗
Physical activity of asthmatic and nonasthmatic children.
Questionnaires examining behaviors and attitudes related to physical activity and asthma were administered to 408 urban schoolchildren aged 11-13 years. Asthmatics (16% of the sample) were more frequently active and were more anxious prior to exercise than nonasthmatics, but did not differ significantly from nonasthmatics in enjoyment of exercise or in physical self-concept. The motives for performing exercise or sport were similar in the two groups, although the asthmatics perceived less pressure to be active from parents or school than the nonasthmatics. It is concluded that asthmatic children have favorable behaviors and attitudes in relation to exercise and sport.
Adolescent↗
An exercise performance test does not measure physical fitness for the average person.
One hundred and thirty five members of the public who attended a medical school open day and who volunteered for a physical fitness assessment were asked to rate their own physical fitness and to give a reason for their rating; subjects then performed a submaximal exercise test for an estimation of maximum oxygen uptake. More than two-thirds of the reasons given for self-rating of fitness were related to level of regular exercise, while physical exercise performance, health or obesity each accounted for 10% or less of the reasons given. There was no significant correlation between self-rating of fitness and maximum oxygen uptake. It is concluded that for the average person an estimate of the level of regular exercise is likely to be a more appropriate measure of physical fitness than performance in an exercise test.
Adult↗