Biology subjects

Kida, N.

Publications and source records attributed to Kida, N..

4 recordsLinked to original sources

bioRxiv2025

Effects of contrast water therapy on performance, circulatory function, and fatigue in collegiate freestyle swimmers

This study aimed to examine the effects of contrast water therapy (CWT) on recovery following high-intensity interval training in competitive collegiate swimmers. Fifteen male freestyle swimmers (mean age: 19.3 {+/-} 1.1 years) participated in a crossover design, performing five 100-meter maximal-effort intervals under two conditions: CWT and passive rest (PAS). Each session included standardized warm-up, pre- and post-intervention measurements of blood pressure (BP), blood lactate concentration (LA), and subjective fatigue (FAS), followed by a second interval set. CWT consisted of 10 cycles of hot (40-41 {degrees}C, 60 s) and cold (20-21 {degrees}C, 30 s) full-body immersion. Performance metrics--swim time, stroke count, stroke length, and stroke velocity--were recorded during both interval sets. The results showed no significant differences between CWT and PAS in swim performance or blood pressure. However, a significant interaction was observed in stroke length during the first interval set, indicating a potential subtle benefit of CWT on swimming mechanics. Importantly, blood lactate concentrations were significantly lower after CWT compared to PAS (p < .001), and subjective fatigue was also reduced. These findings suggest that CWT promotes metabolic recovery, likely through enhanced peripheral circulation and lactate clearance, without negatively affecting cardiovascular parameters. Although CWT did not enhance immediate performance, its ability to reduce physiological and perceptual fatigue indicates its value in managing accumulated fatigue during training cycles. In conclusion, contrast water therapy appears to be a practical and effective recovery strategy for competitive swimmers, especially in supporting lactate clearance and reducing fatigue following high-intensity training. Future studies should explore optimal immersion protocols and assess long-term benefits across varied performance levels.

physiology↗

bioRxiv2024

Evolution of Key Factors Influencing Performance Across Phases in Junior Short Sprints

Sprint performance plays a crucial role in various sports. Short sprints vary in court size and competitive characteristics but are common in many sports. Although the relationship between age and muscle strength has been explored in short sprints, there is limited understanding of how various physical factors interact, particularly concerning differences in the acceleration phase. This study examined the relationship between sprint times at 0-2.5 m, 2.5-5 m, and 5-10 m intervals and various factors in junior athletes. Results indicated that sprint times increased with age, and is correlated with muscle strength and flexibility. Partial correlation analysis showed that faster times in the 0-2.5 m interval were associated with higher hip flexibility; in the 2.5-5 m interval, faster times were associated with higher core flexibility; and in the 5-10 m interval, a relationship with standing long jump performance was confirmed. Furthermore, lower fat-free body weight translated to higher performance. In the acceleration phase of 10 m, flexibility immediately after the start and the subsequent horizontal propulsive force is important factors that are strongly related to performance change in each interval. The study results illuminate the mechanism behind short sprints in junior athletes and emphasize the importance of daily training, considering the sprint distance required for each sport.

animal behavior and cognition↗

bioRxiv2023

Impact of body image on the kinematics of gait initiation

In our daily lives, we walk naturally because we can consider our physical characteristics and formulate appropriate motor plans. However, the impact of changes in body image during motor planning on walking movements remains poorly understood. Therefore, in this study, we investigated how walking movements change when body image is altered. We included 26 participants (13 males, 13 females, aged 18.27{+/-}0.52) to perform walking movements under five conditions: open eyes (baseline), closed eyes, closed eyes while imagining their bodies becoming large, closed eyes again, and open eyes again. As a result, under the condition where participants imagined their bodies becoming large, their stride length, step completion time, and foot lift height increased. These results are attributed to the disparity between actual body size and body image, which affects motor planning. The results of this study have potential applications in rehabilitation and sports coaching settings.

animal behavior and cognition↗

bioRxiv2023

Direction and distance dependency of reaching movements of lower limb

Efficient movement of the body is an important part of our daily lives, which we perform unconsciously. Such efficient movements have been investigated using reaching movements in the upper limb, and whose kinematics reportedly vary depending on the movement direction. However, the reaching movements of the lower limbs are not well understood. Therefore, we aimed to examine changes in the kinematics of the lower limb reaching movements to determine the mechanism of skilled motor ability in terms of direction and distance. Sixteen adults (10 males) were requested to reach targets projected on the floor in seven directions and at three distances, for a total of 21 points. We found that the reaching time slowed down for the contralateral side (right foot to left-sided target), and was caused by a slower start of the toe movement. To identify the cause of this delay, we analyzed the onset of movement at each joint and found that movement to the contralateral side began closer to the torso than movement to the ipsilateral side. The time-to-peak velocity was also calculated; the motion required to reach the target in the shortest time varied depending on the direction and distance. Acceleration phases that were not observed in the upper limb velocity profile were observed in the lower limb velocity profiles. These results suggest that movement kinematics vary with direction and distance, resulting in slower reaching time on the contralateral side.

animal behavior and cognition↗