Abstract
This study aims to investigate the effect of changes in buoyancy when a swimmer respires in a horizontal posture. We attempted to evaluate the levelness of swimmers’ streamline posture by simultaneously measuring the lung capacity and buoyancy under water. The buoyancy was measured based on the changes in the vertical loads of the upper and lower limbs on the subjects’ streamline posture under water. The horizontal x-axis as lung ventilation and the vertical y-axis as buoyancy forms a linear equation y = ax + b. The relation between hand (upper-limb) buoyancy and lung ventilation is defined as y = a1x + b1 and that between foot (lower-limb) buoyancy and lung ventilation as y = a2x + b2. Horizontal levelness was calculated as a ratio by dividing a2 by a1 using the inclination (a) values from these formulas for an underwater streamline posture. We defined this ratio as the breathing–balance (BB) ratio. Although the performance levels in the present study did not show any difference in the absolute quantity of air that humans can inhale in a streamline posture, the BB ratio was higher in a statistically significant manner in junior swimmers competing at international levels compared with the other groups of subjects (P < 0.001). This statistical difference in horizontal levelness, despite the absence of a noticeable difference in the absolute quantity of inhaled air, may be attributable to the way in which each person inhales and exhales air. Top-level junior swimmers that exhibited a high BB ratio might have inhaled in a way that would counteract the sinking of the lower limbs, for example, through abdominal respiration. When exhaling, on the other hand, they might have let out air gradually to mitigate the acceleration force involved in submerging the lower limbs.
Highlights
The average upper-limb torque (TF1) at the time of complete expiration was 11.4 ± 3.2 N m for the junior top swimmers (JTS) group, 10.4 ± 2.8 N m for the collegiate swimmers (CS) group, and 11.8 ± 2.8 N m for the NS group
The average lower-limb torque (TF2) was −16.8 ± 2.3 N m for the JTS group, −15.2 ± 2.8 N m for the CS group, and −17.6 ± 2.9 N m for the NS group; a statistical analysis of these values revealed no statistically significant difference between the three groups (Fig 5A)
The average TF1 during maximum ventilation was 12.8 ± 4.3 N m for the JTS group, 7.9 ± 2.7 N m for the CS group, and 7.0 ± 3.2 N m for the NS group (F (2, 23) = 6.013, p < 0.01)
Summary
For instance, a swimmer is able to effectively utilize his or her buoyancy, the swimming performance will improve. Several reports have reported that buoyancy intervention, for instance, artificially adding buoyancy, positively influences the swimming performance in terms of factors such as swim time, energy cost, and drag force [3], Toussaint et al [4], Zamparo et al [5]).
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