Open Water Swimming: Swimmers Kinematical and Neuromuscular Characterization in 5 km

This study aimed to characterise and analyse the kinematic parameters and muscle activity of swimmers in Open Waters swimming (OWS). 9 male swimmers (age: 25.4 ± 11.9 years; body mass: 75.9 ± 9.0 kg; height: 180.7 ± 6.7 cm; arm span: 185.6 ± 10.3 cm) were evaluated in an open environment (lake), performing 5 x 1000 m at maximum intensity, with a rest of 30 seconds every 1000 m. For kinematical analyses, stroke rate (SR), swimming velocity (v), stroke length (SL), and stroke index (SI) were calculated. Surface EMG data were recorded in 7 muscles: Upper Trapezius (UP); Latissimus dorsi (LD); Pectoralis Major (PM); Posterior Deltoid (PD); Anterior Deltoid (AD); Triceps Brachii (TB); Biceps Brachii (BB) for underwater and recovery phases of the stroke. SL (F=3.41, p=0.06, η2=0.30) and SI (F=3.29, p=0.08, η2=0.29) changed along the distances covered, SR (F=1.54, p=0.24, η2=0.16) increased, especially in the last 1000 m (32.5 ± 3.0 cycles-min-1). AD was highly activated in recovery, showing statistical differences from the beginning (p≤0.01) to the end of the race (p=0.03). The TB muscle was mostly recruited in the underwater phase, from the start (p≤0.01) to the finish (p=0.03), showing a significant difference in each lap, with a large effect. LD showed significant differences in muscle activation, from 1000 m (p≤0.01) with a huge effect, and 5000 m (p≤0.01), with a large effect. These results suggested that the UT and AD muscles had higher activity in recovery than underwater phase, and TB and LD were higher in the underwater phases.