Author(s): CHALCHAT, E., ALGOURDIN, P., SERRALHEIRO, A., CASTAGNA, O., SCHMID, B., JOLIFF, Y., OSTRE, B., Institution: INSTITUT DE RECHERCHE BIOMÉDICALE DES ARMÉES, Country: FRANCE, Abstract-ID: 604

INTRODUCTION:
Scuba diving is an activity that is increasingly practiced, whether in a sport, professional, or military context. Among the well-known criteria that influence diver performance, body kinematics and muscle activity are particularly important. These two parameters are directly related to the energy cost of the diver, which is an important factor in performance. Understanding the biomechanics of this atypical sport in ecological conditions allows for correcting improper posture, thereby improving performance. However, the literature on the subject is still limited. Recent advances, such as the development of new waterproof sensors, promise significant progress in the field of kinematic and muscle activity analysis. The purpose of this study is to describe the kinematics and muscle activation patterns of fin swimming in professional divers.
METHODS:
Eight professional military divers participated in the study. Participants swam underwater for 30 min in a counter-current pool at a pace of 4 min per 100 meters. Divers performed swimming trials using diving fins while wearing waterproof sensors to record both kinematic and muscle activity data. Kinematics were measured using seven inertial measurement units (IMUs) placed on both feet, both shins, both thighs, and on the pelvis. Muscle activity was recorded using surface electromyography (EMG) on the rectus femoris (RF), vastus lateralis (VL), biceps femoris (BF), semitendinosus (ST), gastrocnemius medialis (GM), soleus (Sol), tibialis anterior (TA), and the gluteus maximus (Glut). EMG data were normalized to the maximum activation obtained during a maximal voluntary contraction (MVC). Cardio-respiratory data, including heart rate (HR) and oxygen consumption (VO2), were also monitored.
RESULTS:
The kicking cycle was divided into two phases: the downward phase (0-50 %) and the upward phase (50-100 %). The joint amplitudes for ankle, knee, and hip were 25 ± 10 °, 85 ± 12 °, and 10 ± 4 °, respectively. The maximum angle for the knee was reached at the start of the stroke cycle. The maximum angles for the ankle and hip were reached at 15 % and 18 % of the stroke cycle, respectively. The minimum angles for the knee, ankle, and hip were reached at 50 %, 78 %, and 70 % of the stroke cycle. The average peak EMG activation occurred during the downward phase for the RF (33 ± 14 %MVC), VL (17 ± 6 %MVC), and TA (15 ± 8 %MVC) muscles, and during the upward phase for the GM (32 ± 11 %MVC), Sol (29 ± 10 %MVC), BF (47 ± 19 %MVC), ST (21 ± 4 %MVC), and Glut (4 ± 3 %MVC) muscles. After 5 minutes, the HR and VO2 stabilized, averaging 105 ± 10 bpm and 18.1 ± 2.0 mL·min-1·kg-1, respectively.
CONCLUSION:
This study provides a detailed analysis of both kinematics and muscle activity during scuba diving kicking. This knowledge is essential for teaching proper technique and providing appropriate training protocols to enhance the performance of sport, professional, or military divers.