Alactic vs. Lactate Training
Whether you're pounding out a set of heavy squats, sprinting a hundred meters or sweating your way through an interval workout, short bursts of all-out exercise cause your muscles to expend energy quickly. During high-intensity exercise, aerobic metabolism can't keep up, so muscles utilize two faster, anaerobic, metabolic pathways, which do not require oxygen: the alactic system and the lactate system. By varying the length of your exercise and recovery periods, you can target your training to either the alactic or lactate system.
Your cells store energy in the form of a compound called adenosine triphosphate, or ATP. Muscle cells store only enough ATP to fuel a few seconds of maximal work. However, they also store another compound called creatine phosphate, which rapidly replenishes ATP. Together, ATP and creatine phosphate comprise the alactic anaerobic energy system. The alactic system can supply energy for up to 10 seconds of muscle contraction. Once ATP and creatine phosphate stores are depleted, they must be replenished, either aerobically or through the lactate system.
Muscle cells metabolize carbohydrates for energy by a process called glycolysis. The end product of glycolysis is a compound called pyruvate. Glycolysis is fast but inefficient, producing just two molecules of ATP from a single molecule of glucose, or blood sugar. When muscle cells have sufficient oxygen, they can break down pyruvate aerobically to yield many more ATP molecules. However, when oxygen isn't available, your cells convert pyruvate into lactic acid, which can accumulate in the form of lactate. Although lactate does not directly cause fatigue, when lactate builds up to high levels in your tissues during intense exercise, exhaustion quickly follows.
Because ATP and creatine phosphate are so rapidly depleted, to train the alactic energy system, focus on brief, all-out efforts that last under 10 seconds, such as short sprints, vertical jumps and heavy weightlifting sets. Allow sufficient recovery time between bouts so that your muscles can start to replenish their ATP and creatine phosphate stores before the next round. A good interval ratio to train the alactic system is 1:3, or 10 seconds of work followed by 30 seconds of recovery.
To train the lactate system, you'll need to overload it with all-out bouts of exercise lasting up to a minute, such as 200 to 400 meter dashes or 100 meter swims. Multiple short bouts of intense exercise cause "lactate stacking," resulting in higher blood lactate levels than are possible with a single bout of exercise. Stop about 30 seconds before you reach complete exhaustion. Give yourself three to five minutes of recovery before repeating the routine.
- Exercise Physiology for Health, Fitness and Performance; Sharon A. Plowman and Denise L. Smith
- Exercise Physiology: Energy, Nutrition and Human Performance; William D. McArdle et al.
Joe Miller started writing professionally in 1991. He specializes in writing about health and fitness and has written for "Fit Yoga" magazine and the New York Times City Room blog. He holds a master's degree in applied physiology from Columbia University, Teacher's College.