Relationship between Respiratory Movements and Energy Efficiency in the Post-Exercise Recovery Phase.

The breathing movement is highly automated but it can be voluntarily controlled in some situations. Compared with period of exercise and post-exercise, subjects could control breathing more voluntarily in the post-exercise recovery phase. So, we analyzed relationship between the strategy for controlling the breathing movement pattern and energy efficiency in this phase. Fifteen healthy men (mean age, 22.1 years) were subjected to exercise with a bicycle ergometer at 100 W for 5 minutes, then respiratory pattern was measured four times for 5 minutes after exercise. The measurement items were 1) chest expansion, 2) abdomen expansion, 3) tidal volume, 4) respiration rate, 5) minute ventilation, 6) oxygen intake, and 7) heart rate. The items 1) and 2) were measured by a three-dimensional motion analysis system, and the items 3) through 7) were measured by a respiratory gas analyzer. As for the breathing movement pattern, there were differences among the subjects in terms of the rates of increase in chest expansion and in respiration rate after exercise. The subjects were classified into 4 groups according to these differences. The group, in which respiration rate was increased, showed the marked increase in minute ventilation and oxygen intake, and the rapid recovery of heart rate. The group, in which chest expansion rate was increased, on the other hand, showed small increase in minute ventilation and oxygen intake, and the slow recovery of heart rate. The breathing strategies which are beneficial to energy efficiency exist, however, healthy men do not always select the beneficial strategies.