Is the kinematic of the trunk during the forehand in tennis still disrupted in women at one year postpartum?

The number of female athletes (♀) has shown significant growth in the recent Olympics. The percentage of ♀ has increased from 18 % in Seoul (1988) and 38 % in Sydney (2000) to 44 % in the London Olympics (2012). It is not so unusual that elite athletes have a child during their high level career. However, throughout pregnancy (P), ♀ cannot continue their training pace as before (Clapp, 2000). These influence their physical capacity and reduce their athletic performance in postpartum (PP) and / or delay the return to a pre-P performance level. In contrast, Beilock et al. (2001) show that maintaining a certain level of cardiovascular and muscle strength during P can help athletes to quickly return to competition in PP. Tennis is a sport that significantly solicits the trunk to produce its technical gestures (Ellenbecker 1996). Indeed, to a large extend, the transfer of kinetic energy from the legs to the racket depends on a suitable rotation of the trunk. The trunk is the part 'hinges' in the kinetic chain to develop and transfer the power from the legs to the racket during the strike (Roetert & Groppel 2001). Several studies on pregnant ♀ show that the trunk is the most affected part by the morphological changes during P. This is especially due to a relaxation in articulations ligaments because of the hormonal changing (Clapp et al. 1989) but also decreased activity during P. Forehand is the second most common technical gesture in tennis. It requires ‘good’ trunk rotations for its completion (Johnson, 2006). The angle of trunk rotation in the transverse plane at the end of the preparation phase is quantized to 104° (shoulder line relative to the bottom line of tennis court; Kibele et al. 2009). We hypothesize that a strengthening program centered on the trunk during P could help to quickly return to the initial level of technical performance before P.