Anaerobic capacity determined by maximal accumulated O2 deficit.

We present a method for quantifying the anaerobic capacity based on determination of the maximal accumulated O2 deficit. The accumulated O2 deficit was determined for 11 subjects during 5 exhausting bouts of treadmill running lasting from 15 s to greater than 4 min. The accumulated O2 deficit increased with the duration for exhausting bouts lasting up to 2 min, but a leveling off was found for bouts lasting 2 min or more. Between-subject variation in the maximal accumulated O2 deficit ranged from 52 to 90 ml/kg. During exhausting exercise while subjects inspired air with reduced O2 content (O2 fraction = 13.5%), the maximal O2 uptake was 22% lower, whereas the accumulated O2 deficit remained unchanged. The precision of the method is 3 ml/kg. The method is based on estimation of the O2 demand by extrapolating the linear relationship between treadmill speed and O2 uptake at submaximal intensities. The slopes, which reflect running economy, varied by 16% between subjects, and the relationships had to be determined individually. This can be done either by measuring the O2 uptake at a minimum of 10 different submaximal intensities or by two measurements close to the maximal O2 uptake and by making use of a common Y-intercept of 5 ml.kg-1.min-1. By using these individual relationships the maximal accumulated O2 deficit, which appears to be a direct quantitative expression of the anaerobic capacity, can be calculated after measuring the O2 uptake during one exhausting bout of exercise lasting 2-3 min.

Effect of different post-exercise sugar diets on the rate of muscle glycogen synthesis.

The effect of repeated ingestions of fructose, sucrose, and various amounts of glucose on muscle glycogen synthesis during the first 6 h after exhaustive bicycle exercise was studied. Muscle biopsies for glycogen determination were taken before and after exercise, and every second hour during recovery. Blood samples for plasma glucose and insulin determination were taken before and after exercise, and every hour during recovery. When 0.35 (low glucose: N = 5), 0.70 (medium glucose: N = 5), or 1.40 (high glucose: N = 5) g.kg-1 body weight of glucose were given orally at 0, 2, and 4 h after exercise, the rates of glycogen synthesis were (mean +/- SE) 2.1 +/- 0.5, 5.8 +/- 1.0, and 5.7 +/- 0.9 mmol.kg-1.h-1, respectively. When 0.70 g.kg-1 body weight of sucrose (medium sucrose: N = 5), or fructose (medium fructose: N = 7) was ingested accordingly, the rates were 6.2 +/- 0.5 and 3.2 +/- 0.7 mmol.kg-1.h-1. Average plasma glucose level during recovery were similar in low glucose, medium glucose, and high glucose groups (5.76 +/- 0.24, 6.31 +/- 0.64, and 6.52 +/- 0.24 mM), while average plasma insulin levels were higher with higher glucose intake (16 +/- 1, 21 +/- 3, and 38 +/- 4 microU.ml-1).(ABSTRACT TRUNCATED AT 250 WORDS)

Effect of duration of exercise on excess postexercise O2 consumption.

This study was undertaken to determine the effect of exercise duration on the time course and magnitude of excess postexercise O2 consumption (EPOC). Six healthy male subjects exercised on separate days for 80, 40, and 20 min at 70% of maximal O2 consumption on a cycle ergometer. A control experiment without exercise was performed. O2 uptake, respiratory exchange ratio (R), and rectal temperature were monitored while the subjects rested in bed 24 h postexercise. An increase in O2 uptake lasting 12 h was observed for all exercise durations, but no increase was seen after 24 h. The magnitude of 12-h EPOC was proportional to exercise duration and equaled 14.4 +/- 1.2, 6.8 +/- 1.7, and 5.1 +/- 1.2% after 80, 40, and 20 min of exercise, respectively. On the average, 12-h EPOC equaled 15.2 +/- 2.0% of total exercise O2 consumption (EOC). There was no difference in EPOC:EOC for different exercise durations. A linear decrease with exercise duration was observed in R between 2 and 24 h postexercise. No change was observed in recovery rectal temperature. It is concluded that EPOC increases linearly with exercise duration at a work intensity of 70% of maximal O2 consumption.

Muscle glycogen depletion patterns in type I and subgroups of type II fibres during prolonged severe exercise in man.

Glycogen depletion of muscle fibre types I, II A, II AB and II B was studied using a histochemical method to quantify glycogen content in individual fibres. The reliability was examined in 29 muscle biopsies, in which total glycogen content was compared to average periodic acid Schiff (PAS) stain intensity in sections from the same samples. Over a wide range of glycogen content (1-252 mmole glucosyl units . kg-1 wet weight) a linear relationship (r = 0.93) was found between the two methods for quantification of muscle glycogen. Glycogen depletion patterns in type I, II A, II AB and II B fibres were studied in 5 subjects during exhaustive bicycle exercise at 75% of VO2 max. At rest before exercise glycogen content was 16% higher in type II subgroups than in type I (p less than 0.05). From start of exercise the same glycogen depletion rate was observed in type I and II A. Glycogen content of Type II AB and II B was unchanged during the first part of exercise. Later a decrease was observed, first in type II AB and finally in II B, suggesting a decrease in threshold force of these fibre types. The results indicate physiological differences between the 3 subgroups of type II fibres in man, whereas at the present exercise intensity type I and II A fibres were recruited simultaneously from start.

Rowing performance, a mathematical model based on analysis of body dimensions as exemplified by body weight.

The theory of body dimensional influence on muscular work is employed for calculating the racing time of heavy- and lightweight male, and female rowers. The developed equation predicts racing results with an accuracy of 1 s +/- 1.7 (SE). The prediction of a 2.6% advantage of the heavyweights (average bodyweight) 93 kg over the lightweights (70 kg) is in excellent agreement with observations (2.5%). Significant implications of the equation would be to row without a coxswain, to reduce boat weight to a minimum, and to increase racing distance e.g., for females to the racing distance rowed by the males (2,000 m) in order to reduce the influence of body dimensions on rowing performance.

Metabolic responses to bicycle exercise after several days of physical work and energy deficiency.

The responses of plasma free fatty acids (FFA), free glycerol, beta-hydroxybutyrate (BUT) and glucose to bicycle exercise (corresponding to 50% of the maximal VO2) were investigated in 11 cadets of the Norwegian Military Academy, before a combat course (control experiment) and on the third and fifth day of such a course which involved nearly continuous intense military activities and pronounced energy deficiency. Pre-exercise levels of FFA, glycerol and BUT were greatly elevated on days 3 and 5 as compared with pre-exercise levels before the course. The increases in plasma FFA, glucose and BUT in response to bicycle exercise were much more pronounced on days 3 and 5 than before the course. The increases observed during (and before) the course were approximately in mmol/l: FFA 1.0 (0.3), glycerol 0.3 (0.08), BUT 0.6 (0.0). The day 5 responses were lower than those on day 3. The plasma glucose concentration appeared to decrease slightly after exercise on days 3 and 5. The results demonstrate that several days of strenuous work and pronounced energy deficiency do appreciably increase acute metabolic responses to exercise, and indicate that there is a very high FFA-utilization under such conditions.