Aerobic exercise, anaerobic exercise and the lactate threshold

Abstract

All exercise draws first on intramuscular stores of ATP and creatine phosphate; initially these are replenished by anaerobic glycolysis. The lactic acid produced contributes to the rapid development of fatigue in high intensity exercise. Aerobic metabolism (at first mainly of glycogen, later increasingly of fat) is the principal route of ATP resynthesis in activities lasting longer than 2 min, but can only maintain work-rates about 1/4 of those possible in very brief bursts. Blood lactate rises at the higher aerobic work rates. 'Lactate threshold' (LT: approximately 2 mmol/l) is almost exactly the speed at which endurance races are won, and close to those apparently providing optimal aerobic training. This training, predominantly of muscle aerobic capacity, elevates LT more than maximum oxygen consumption. LT is not now thought to indicate oxygen-deprivation, but intracellular adjustments driving oxidative phosphorylation faster. Ventilatory breakpoints, formerly considered to indicate LT, correlate more closely with the accumulation of potassium than lactate.

Detection of ischemia by Pco2 before adenosine triphosphate declines in skeletal muscle

“…In noncontracting skeletal muscle cells, increased lactate production indicates insufficient oxygen supply to support the basic need of the cells (dysoxia). In skeletal muscle, during extreme workloads, lactate production occurs despite a large blood supply to the muscle (37)(38)(39)(40)(41). We have chosen a noncontracting model that we consider clinically appropriate.…”

History of developments in sport and exercise physiology: A. V. Hill, maximal oxygen uptake, and oxygen debt

“…The first question is probably adequately answered by repeated constant-load tests over a range of loads. However, work over the last 20 years, reviewed by Spurway (1992) and applied to sports testing (Spurway & Jones, 2007), leads to the conclusion that ''On all accounts . .…”

Effort syndrome: Hyperventilation and reduction of anaerobic threshold

“…The anaerobic threshold has been defined as "the level of work or of oxygen consumption just below that at which metabolic acidosis and the associated changes in gas exchange occur" (Wasserman et al, 1973;Holl-man, 1985;Spurway, 1992). Conventionally it is identified by measurement of lactic acid in the blood or by the threshold increase of CO2 excretion in relation to 02 consumption (Wasserman, Beaver, & Whipp, 1990;Wasserman & Casaburi, 1991).…”