The measurement of plasma catecholamine and lactate thresholds: a comparison of methods.

Plasma lactate and catecholamine thresholds were calculated using three different variations of linear regression, an algorithmic linear regression method, a log-log transformation method and a semi-log method. A group of 18 male sports science students undertook an incremental test to exhaustion on a cycle ergometer. A 5-ml blood sample was drawn at rest, after 4 min of exercise and every 2 min thereafter until the cessation of the test. Lactate, adrenaline and noradrenaline concentrations were measured. Lactate threshold (Th1a), adrenaline threshold (ThA) and noradrenaline threshold (ThNA) were calculated using each of the three methods. The best fits of the methods were examined by comparing their standard error of estimates (SEEs). The algorithmic method demonstrated a higher SEE than the other two methods, but only for Th1a and ThNA. The power output for which each method calculated the thresholds demonstrated a main effect for method. Tukey post hoc tests showed that the algorithmic method produced significantly higher outputs than the other two methods, which did not differ significantly from one another. Comparison of these power outputs showed that Th1a and ThA differed significantly, regardless of method, there were no other significant differences. Plasma concentrations of lactate, adrenaline and noradrenaline showed that the values of Th1a and ThNA calculated by the algorithmic method were significantly higher than those calculated using the other two methods, which did not differ significantly from one another. The only significant difference for ThA was between the algorithmic and semi-log methods. Correlations between the power outputs at which each method calculated the thresholds varied greatly between methods, and were at best only moderate (r = 0.63). It was concluded that the algorithmic method was less powerful than the other two methods, and that Th1a, ThA and ThNA are not highly correlated.

Exercise, plasma catecholamine concentrations and decision-making performance of soccer players on a soccer-specific test.

The main aim of this study was to compare the decision-making performance of college soccer players on a soccer-specific, tachistoscopically presented test, at rest and while exercising at their adrenaline threshold and at their maximum power output. These were determined following an incremental test to exhaustion on a cycle ergometer. After the initial maximum power test, participants (n = 9) were allowed 10 habituation trials on the soccer decision-making test. Participants' decision-making performance was tested at rest, while cycling at a power output that had previously been determined to elicit their adrenaline threshold and while cycling at maximum power output. Accuracy and speed of decision were the dependent variables. A one-way repeated-measures analysis of variance showed no significant effect of exercise on accuracy, and showed speed of decision to be significantly affected by exercise. Tukey post-hoc tests showed that speed of decision at rest was significantly slower than in the other two conditions, which did not differ significantly from one another. Based on allocatable resources theories of arousal and performance, we conclude that the adrenaline threshold may be indicative of increases in the resources available to the individual. Furthermore, we considered that exercise at maximum power output may only induce a moderate rather than a high level of arousal.

The effects of acute phosphate supplementation in subjects of different aerobic fitness levels.

Six trained cyclists (high-fitness group) and six untrained individuals (low-fitness group), performed a 20-min cycle ergometer exercise test at 70% of maximum oxygen consumption (VO2max) followed by a 30-min rest period and then an incremental ride to exhaustion on two occasions, 1 week apart. Ninety minutes prior to exercise subjects consumed a drink containing either 22.2 g dibasic calcium phosphate (DCP; treatment) or calcium carbonate (placebo). Blood was drawn prior to drink ingestion, during submaximal exercise, during recovery and at exhaustion for determination of blood 2,3-DPG, blood ATP, plasma lactate, plasma phosphate, haemoglobin and haematocrit. Throughout exercise, cardiorespiratory variables [oxygen uptake (VO2), minute ventilation, (VE), respiratory exchange ratio, heart rate and oxygen pulse] were monitored, and ratings of perceived exertion obtained. Although there was a trend for the low-fitness group to have a higher plasma phosphate concentration prior to treatment ingestion, no treatment effects on plasma phosphate were noted at any sample time in either group. 2,3-DPG, VO2, oxygen pulse, VE, time to exhaustion and VO2max were significantly higher in the high-fitness group; however, no differences in these variables were observed as a result of phosphate ingestion. Plasma lactate was significantly lower in the high-fitness group during the submaximal exercise and the recovery period, but again phosphate ingestion had no effect. These results suggest that acute DCP supplementation is not effective as an ergogenic aid and that aerobic fitness level does not affect the response to phosphate supplementation.

Modifications to hydra-gym equipment provide for clinically useful strength measurements.

Modifications were made to the Series III-311 Omnikinetic Hydra-Gym apparatus (Hydra-Fitness Industries Inc., Belton, TX) in an effort to provide relatively inexpensive yet clinically useful isokinetic strength measurements. Signal transmission and processing functions were installed to calculate relevant strength characteristics for knee extension/flexion motions. Results from the modified Hydra-Gym were compared with matched procedures on the Kin-Com (model 500-10, Chattecx Corporation, Chattanooga, TN). Subjects (N = 10) performed three maximal concentric right knee extension/flexion cycles at different resistance settings (2, 4, and 6) on the Hydra-Gym and the corresponding angular velocities on the Kin-Com (190, 125, and 40 degrees/sec, respectively). Each subject completed eight testing sessions, four on each dynamometer. A five-way analysis of variance on the peak torque data revealed no significant difference between dynamometers; however, there was a significant interaction between dynamometer and extension/flexion measurements. The variance in angle of peak torque data was significantly different between dynamometers, with Hydra-Gym showing superior reproducibility (p < 0.005). Mechanical differences between dynamometers produced slightly different, though comparable and consistent, measurement values. Care must be taken when evaluating hamstring/quadriceps ratios from the Hydra-Gym because the interaction noticed between dynamometer and extension/flexion may exaggerate muscle imbalances. In summary, modifications to the Hydra-Gym appear to provide clinicians with a reliable and clinically useful strength testing alternative.

Ergogenic effects of phosphate loading: physiological fact or methodological fiction?

Inorganic phosphate (Pi) supplementation has been reported to provide ergogenic benefits, though the research findings are inconsistent. Several confounding influences may explain these results, including mode of exercise, exercise intensity, dietary intake, daily biological fluctuations, type of supplement, administered dose of the supplement, washout period, length of loading period, fitness level of subjects, blood volume alterations, and sample collection and analysis techniques. This review provides a critical analysis of the methodological difficulties that may contribute to the equivocal research findings pertaining to Pi supplementation.

Energy balance of nutrition and activity in a group of nursing students.

This descriptive study presents a profile of energy balance, nutrition, and activity in a group of baccalaureate nursing students (N = 21). Self-reported, consecutive, three-day food and physical activity records as well as a background questionnaire served as the instruments for data collection. Findings revealed that energy intakes were adequate to meet recommended nutrient intakes for all nutrients except carbohydrate, but insufficient to meet their levels of energy expenditure. Student involvement in a range of activities that required substantial energy expenditure, coupled with weight-loss dieting by several students appear to explain this observed energy imbalance. Increased carbohydrate intake and decreased fat intake would seem to be recommended nutritional modifications warranted for this group of nursing students.

Physiological profiles of the Canadian Olympic Hockey Team (1980).

In order to establish baseline data and to prescribe training programmes to off-set weaknesses, selected measures of aerobic fitness (VO2max), muscular power (peak torque and watt output) and performance times on-ice were collected on the Canadian Olympic Hockey Team (1980). VO2max values (54 ml. kg. min) were similar to other non-endurance athletes. Peak torque values relative to body weight in knee extension at 30 degrees and 180 degrees . s-1 (3.62 an 1.85 Nm . kg-1) were the same at low speed but lower at high speed than other selected power athletes. The on-ice performance times showed higher speed of over 180' than professional and junior level players but the speed drop-off over six repeats was greater. There were no differences between positions on these measures. These data offer a baseline from which to compare other hockey players and suggest that the aerobic fitness levels and torque outputs at high speed are not well developed.

lsokinetic Torque Outputs of Professional and Elite Amateur Ice Hockey Players.

Instrumentation advances have recently allowed the isokinetic evaluation of muscle function for purposes of injury diagnosis, rehabilitation, and training prescription. This type of evaluation has been particularly useful for athletes in preparing for performance or returning to training following injury. lsokinetic testing of specific muscle groups and at the approximate limb speeds required for performance of the sport has allowed more specific analysis of the functional strengths and weaknesses of athletes. Isokinetic testing allows comparison of agonist and antagonist muscle groups for balance across a joint, for right and left side muscle group comparison, and for joint angle at peak torque. Several athletic groups have already been characterized; alpine skiing, track and field (sprinting, jumping, and walking), and orienteering. The purpose of this study was to evaluate the function of important muscle groups for the performance of ice hockey. The data provided the basis for devising a training program for the athletes and also provided data for the characterization of professional (NHL) and elite amateur (Olympic) ice hockey players. Analysis also provided comparative information about the two groups.J Orthop Sports Phys Ther 1981;3(2):42-47.