Applied Exercise Physiology: Maximal Exercise Lasting From 16 to 39 Seconds

The metabolic response for maximal exercise in the range of 16 to 39 seconds results in the following physiological changes:

ATP                  -36%

PC                    -70%

Lactate              +15-21 mmol/L

Glycogen           -16%

PC are significantly depleted here due to the high amounts of ATP required to produce energy. Lactate concentration rises to very high concentrations during this type of exercise, which is a result of the high rate of energy production. Muscle glycogen stores are beginning to deplete in this time frame. This is as a result of the dominant system being the anaerobic glycolysis system where muscle glucose is broken down and used to help with ATP resynthesis.

The contribution from the energy systems is as follows:

Creatine phosphate (CP)             18%

Anaerobic glycolysis                    47%

Aerobic                                     35%

Both the CP and glycolitic systems are both anaerobic and are required because the intensity of exercise in this time frame is around 195% of the athletes maximum oxygen consumption (VO2 max).

The top sprint cyclists are able to produce large amounts of energy in this time. Values can reach a maximum of 1400 watts with averages over 30 seconds around 660 watts. Eccentric exercise involved in running can cause micro tears in the muscle fibers, therefore increases in growth hormone are observed about 1 hour after exercise.

Limiting factors

The depletion of PC stores causes the maximal power to drop as the body begins to use the glycolytic system and produces energy at a slower rate. High concentrations of hydrogen ions cause the pH of the muscle to drop and become more acidic therefore interfering with enzymatic activity and reducing power even further.

PC storage can be increased through correct training (5-10 second intervals with 6 minute recoveries). Tolerance to lactate can also be improved by longer repetitions with shorter rest periods. Aerobic training focusing on improving maximum oxygen consumption may be of good use as a greater aerobic system will allow more training to be done and better recoveries. Also 35% of the energy for this time frame is supplied aerobically during a maximal performance.