Introduction: It has been reported that an important factor for optimal strength generation in tennis strokes is the neuromuscular activation of the muscles mainly involved in each tennis stroke, during the initial phase of arm acceleration (Elliot, Tennis, 2002, 1-29). Neuromuscular activation can be improved with explosive strength training (Häkinen, Strength training for sport, 2002, 20-36). We hypothesize, on the other hand, that the maximal level of dynamic strength can be enhanced or, at least maintained, during the whole competitive season via a well designed strength training program. Therefore, the main purpose of this study was to analyse the effects of tennis competition on the maximal dynamic strength (MDS) in two female professional tennis players (P1 and P2). We present the improvements of MDS after a weight-lifting strength training program (STP) and the evolution of MDS during the competitive phase of the season in two different tennis players who either performed or not a single session of MDS training per week. Methods: Two professional females tennis players from the same population, P1 (22 years, 75.6 kg, 165.5 cm, top 50 WTA ranking) and P2 (15 years, 61.6 kg, 171.5 cm, top 100 WTA ranking), followed a 4 and 12 weeks STP to improve the MDS, respectively. P1 had no previous experience in strength training with weight-lifting exercises. During the training session, both players performed 3 series of 8 repetitions each, executed at maximal speed, at 70-80% of 1 MR, with 5 min rest period between series. During the strength training periods, subjects alternated sessions of upper body (UB) or lower body exercises (LB), with a frequency of 4 sessions/week. During the competitive phase of the season, P1 performed 1 session/week of strength training (1 series of 3 MR per exercise), while P2 did not add any weight-lifting exercises to her training routine. The MDS was measured before (T1) and after (T2) the STP, as well as at the end of the tennis season (TEND) with a test of maximal repetitions (between 3 and 12 repetitions, with 3 different load levels). Afterwards, we determined the 1 MR by extrapolation of the semi-logarithmic relationship load / ln (number of repetitions). Total and regional body composition was measured after the STP and at the end of the tennis season by dual energy X-ray absorptiometry (DXA)(QDR-1500, Hologic Corp., Waltham, MA) (Sanchis Moysi et al., Science and Racket Sports II, 1998, 34-43). Results: Both players improved the MDS in UB and LB exercises. This improvement was higher in P2 than in P1 (126% vs 34% and 79% vs 36% for UB and LB exercises, respectively). Compared with T2, MDS at the end of the season was increased in P1 (UB by 16% and LB by 21%), while MDS decresead in P2 (UB by 18% and LB by 22%). Furthermore, between T2 and TEND, P1 maintained the muscle mass of the upper and lower limbs (2346.6 vs. 2365.4 g, 2140 vs. 2184.3 g, 9100.3 vs. 9192 g, 8746 vs. 8970.9 g, for the left arm, right arm, left leg and right leg, respectively). In contrast, P2 lost some muscle mass (1942.1 vs. 1877.5 g, 2196.5 vs. 2186.7 g, 7175 vs. 7966.4 g, 7647.9 vs. 7574.5 g, for the left arm, right arm, left leg and right leg, respectively). Conclusions: In summary, this study shows that in female professional tennis players the gains of maximal dynamic strength obtained during the preparation phase of the season can be maintained, and even slightly increased, if 1 session/week of explosive strength training is performed during the competitive phase of the season. This improvement of strength was likely mediated via neuromuscular mechanisms, inasmuch as the muscle mass remained unchanged during the competitive season. In contrast, the total elimination of strength training was accompanied by some loss of muscle mass and muscular strength, which can negatively affect performance during the rest of the season.
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