SYMMETRY OF PROPULSION EXERTED DURING TETHERED- AND FREE-SWIMMING

INTRODUCTION Swimming is characterized by body propulsion, where the upper limbs play the role of the main contributor (Zamparo et al., 2020). Recently, the study of the propelling forces involved during the swimming action has been ecologically allowed using wearable pressure sensors. Thus, this study analyzed the propelling forces of the two hands during free (Free) and tethered (Tet) swimming conditions by means of wearable pressure sensors. METHODS Eleven regional-level swimmers (age 15.4±0.5y.; body mass 58.0±7.1Kg; stature 168.4±5.0 cm) performed a 10-sec maximal full-tethered test and a 10-sec free-swimming test at front- crawl only-arms. Two pressure sensors (SEAL, Platysens) were attached to each swimmer’s hand (dorsal and palmar side) to estimate the propelling forces as the horizontal component of the product of differential pressure and hand surface. Propelling forces of each hand in terms of average (FMEAN), impulse (I), peak (FPEAK) and instantaneous (by means of Statistical Parametric Mapping, SPM) values were analysed as a function of swimming condition and dominant/non-dominant hand. Furthermore, the symmetry index (SI) of propelling forces was analysed as a function of swimming condition. RESULTS Larger FMEAN, FPEAK, and I were found during Tet compared to Free condition (F>14.29, p<0.001). SPM highlighted larger FMEAN in Tet condition only at the beginning of the stroke (from 7 to 28% of stroke cycle duration). Additionally, no significant differences were observed for FMEAN and FPEAK between the hands (p>.05). SPM and SI confirm non-significant differences between dominant and non-dominant hands in propelling forces (p>0.05), while larger I was found in the dominant hand (F=11.11, p<.05). DISCUSSION The swimmer appears to exert larger hand propulsion in tethered- than free- swimming. Our experiments reveal a similar symmetry and hands propelling models in the two analysed swimming conditions (Tet and Free) despite the fact that the effect of hand kinematic was not taken into account.