No abstract

Testing procedures for the assessment of anaerobic energy metabolism during muscular work have not yet gained the relevance of tests assessing maximal aerobic power. The diagnosis of aerobic power allows one, through the choice of an adequate testing protocol, to design a test that mainly measures the power of aerobic metabolism by means of indicators like VO 2max and lactate. With regard to tests for the assessment of anaerobic power and capacity, however, alactic, lactic, and oxidative components of energy expenditure as a whole cannot be differentiated by means of simple parameters (e.g., lactate and time until exhaustion). By means of computer simulations of energy metabolism for supramaximal loads with durations until exhaustion of about 10 s and 60 s as well as the isolated variation of the concentration of muscle phosphocreatine, the maximal rate of lactate production, and the maximal aerobic power (VO 2max ), the influence of the single components on energy metabolism as a whole is presented in a semi-quantitative way. Subsequent testing procedures for the measurement of alactic and lactic power as well as alactic and lactic capacity are presented. Finally critical-power method and method for the determination of maximal accumulated O 2 deficit are described in greater detail, because both methods are widely discussed in contemporary international literature.

With the portable spirograph CORTEX X1 both the oxygen consumption and the carbon dioxide output can be determined. Therefore, the aim of the present study was to determine the accuracy of the CORTEX X1 in measuring F(E)O2, F(E)CO2 and V(E) when attached to a motor-driven mechanical syringe and to validate the CORTEX X1 against a standardized breath-by-breath system during a graded bicycle ergometry. Fifteen subjects (8 male, 7 female; 26.7+/-3.3 years) performed two graded exercise tests on a bicycle ergometer (50 W incline every 3 min) until volitional fatigue in randomized order. During rest and during the last 30 s of each step ventilatory and gas exchange parameters were measured with the CORTEX X1 and the OXYCONgamma. At rest and at each step no significant differences exist for VO2 (F = 0.97) and VCO2 (F = 0.90). The orthogonal regression equation of the VO2-values was VO2(X1) = -75.5 + 1.01 x VO2(Oxy) and the equation of the VCO2-values was VCO2(X1) = 21.7-1.008 x VCO2(Oxy). The VO2-max-values were nearly the same: 3569+/-924 ml/min (Oxy) and 3497+/-993ml/min (X1). Similar findings were made with regard to VCO2max 4117+/-1010 ml/min (Oxy) and 4126+/-1090 ml/ min. (X1). Maximal values for heart rate were 181+/-10 beats/ min (X1) and 180+/-8 beats/min (Oxy) (F=0.21), for maximal power 256+/-64 W (X1) and 257+/-63 (Oxy) (F = 0.0001) and for maximal ventilation 118+/-31 l/min) and 120+/-35 l/min (Oxy) (F = 0.03) with no significant difference. When attached to the motor-driven syringe V(E) was accurately measured up to 288 l/ min. Over a period of 40 min there was no drift observed in F(E)O2 and F(E)CO2. In conclusion, with the CORTEX X1 VO2 and VCO2 can be accurately determined.

Maximal lactate steady state (MLSS) presumably corresponds to the highest constant workload that can be performed by oxidative metabolism. The anaerobic and, to a minor extent, the oxidative metabolism have been reported to be affected by age. The second decade of life is the key period in the change in energy metabolism between children and adults. The aim of this study was to evaluate the effects of age on MLSS in 34 male subjects (age: 15.4 +/- 2.8 yr, range: 11-20 yr; height: 171.8 +/- 14.9 cm, range: 134-191 cm; body mass: 59.6 +/- 15.5 kg, range: 27-90 kg) performing an incremental load test to determine maximal workload and several constant load tests for MLSS measurement on a cycle ergometer. MLSS (4.2 +/- 0.7 mmol.l-1, range: 2.8 to 5.5 mmol.l-1) and MLSS intensity related to maximal workload (66.5 +/- 7.7%, range: 50-84%) were independent of age. MLSS heart rate (180.1 +/- 10.1 min-1, range: 156-208 min-1) decreased (P < 0.01) with increasing age, whereas absolute (157.2 +/- 54.8 W, range: 65-240 W) and relative MLSS workload (2.6 +/- 0.5 W.kg-1, range: 1.5 to 4.1 W.kg-1) and absolute (236.9 +/- 79.0 W, range: 100-350 W) and relative maximal workload (3.9 +/- 0.6 W.kg-1, range: 2.7 to 5.5 W.kg-1) increased (P < 0.001) with age. The age independence of MLSS supports the theory that neuromuscular factors may contribute to the frequently observed changes in response to given exercise with physical maturity more than changes in oxidative metabolism and/or glycolysis.