New evaluation index for the retainability of a swimmer’s horizontal posture

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.

Gliding performance is affected by cranial movement of abdominal organs

“…No significant differences in characteristics with regard to height, the length between the tip of the longest finger and the soles of the feet, and BMI were observed between participants in the high performance group and those in the low performance group (Table 4 ). The center of gravity was measured using the reaction board method 10 , 23 , and ground reaction force data were acquired using 90 × 60 cm force plates (Anima Corporation, Chofu, Tokyo, Japan) 24 . The participants were placed on the balance board in the supine position, and measurements were performed in both the streamlined body position and resting position.…”

Differences in the rotational effect of buoyancy and trunk kinematics between front crawl and backstroke swimming

“…In the aquatic environment, the human body is exposed to two vertical forces with opposite direction, namely gravity and buoyancy. When a human holds a horizontal static position in the water, the centre of mass (CM) is located about 2 cm more caudally (towards the legs) than the centre of buoyancy (CB) (Watanabe et al, 2017), thereby producing a rotational torque (buoyant torque) that causes the lower-limbs to sink (Gagnon & Montpetit, 1981;Kjendlie et al, 2004;Payton & Reid, 2014).…”

The Influence of Chest Style Learning Methods on the Decreasing of Students Anxiety Level

“…Swimming is a sport that can be learned by all ages, from babies, children to adults [1]. Naturally humans are able to master swimming skills, because humans have buoyancy [2]. Likewise, the nature of water is able to lift the weight of our body [3], there should be no one who cannot master the swimming movement.…”