RESOLUCIÓN DE INCOHERENCIAS EN LA EVOLUCIÓN DE LOS USOS

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Despite the varying intensity and intermittent nature of wheelchair tennis, HR typically remains elevated throughout the full duration of a match (Kovacs, 2007). Mean average HR is, therefore, a valid indicator of the accumulated physiological stress associated with short, intense bouts of play. A match-play median of 130 ± 26 bmin-1 (range: 109 to 157) was observed in the present study. While these values were higher than those reported previously involving skilled (Roy et al., 2006) and experienced(Barfield et al., 2009) male wheelchair tennis players (122 ± 10 and 121 ± 14 bmin-1 respectively), higher average values of 146 ± 16 bmin-1 have also been reported in an elite, mixed sample (Croft et al., 2010). In relative terms, values of 69 to 75% peak HR have been reported previously for wheelchair tennis match-play (Croft et al., 2010; Barfield et al., 2009; Roy et al., 2006). In this study, the playing intensity was similar in relative terms when direct comparisons were made between HIGH and LOW (72 ± 7 vs. 71 ± 10 %, P = 0.471). As intensities of 60 to 75 % and > 75 % of peak HR are typically associated with moderate and vigorous exercise respectively (Pluim et al., 2007), this study reveals that regardless of ITF rank, tennis players are required to exercise at intensities approaching a vigorous level during match-play. However, relative intensities are best reported after direct measurement of peak responses (Bernardi et al., 2010; Croft et al., 2010; Barfield et al., 2009; Roy et al., 2006) so it should be reiterated that an estimation (220 – age) was applied in the present study. While such an intensity is linked with health-enhancing effects (Bhambhani et al., 1994) and compares favourably to other wheelchair sports (Barfield et al., 2010; Croft et al., 2010; Barfield et al., 2009; Roy et al., 2006), the intense nature of the activity environment raises a series of important considerations regarding participation and player development within the sport. First, as intermittent wheelchair sports depend on a significant contribution from the anaerobic energy pathway (Bhambhani et al., 1994) and tennis is highly dependent on aerobic capacity (Bernardi et al., 2010), elite players typically demonstrate physiological profiles that are representative of a well- trained population (Goosey-Tolfrey et al., 2006). It seems reasonable to assume, therefore, that elite players would be familiar with a moderate to vigorous intensity during match-play. In contrast, novice players who are typically less experienced and less well conditioned may find the intensity requirements more challenging, particularly given the significant skill challenge associated with the sport (Roy et al., 2006) coupled with their slower motor responses (Reina et al., 2007). Second, unlike other wheelchair sports where the physiological demand decreases as the match progresses (Sarro et al., 2010) this study suggests that the demand in tennis is sustained or increased for match duration. This is evidenced by comparable responses across sets 1 and 2 for all variables, and a small ES for APT, which suggests a slight increase in playing time with match progression. Third, there was no rank main effect on APT. This suggests that HIGH and LOW needed to be active for equivalent amounts of time. Finally, a significant main effect for result revealed that mean minimum HR was lower during winning sets. Such a low HR may reflect an ability to maintain a strong court position during match-play. It is accepted that for chronic health benefits, a chronic elevation in HR is

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required, with a strong, graded, inverse association between exercise intensity and relative risk of cardiovascular disease (Manson et al., 2002). It is interesting that the results of this study infer that with increases in skill, players could theoretically be placed at a physiological advantage in terms of match-play outcome, but a disadvantage in terms of exposure to optimal conditions for chronic health enhancement. Further research is required to examine if shot-play and decision-making is associated with decreased court-movement and concomitant physiological responses. Studies involving interventions to encourage increased movement or enhanced shot-play via coaching will, therefore, be important from a health perspective. The benefits of increasing EE through increased PA are widely accepted, with a negative association between levels of weekly PA and all-cause mortality (Paffenbarger et al., 1986). As tennis is an intense sport, and an extended playing time is associated with a greater physiological demand (Croft et al., 2010), consideration should be given to potential strategies to extend playing time, but also to optimise court-positioning during training. Hitting a standard tennis ball without due consideration of the match context in which skills are expressed is likely to be an ineffective training strategy (Reid et al., 2007a).

This study suggests that for accurate match-play profiling, consideration of player rank and playing level is required. Studies restricted to a sample of elite athletes are likely to overestimate the demands for less skilled counterparts, leading to inaccurate training prescription. Generalisations between groups cannot be made in tennis, where the demands are not equal. While there appears to be an equivalency in intensity for rank, there are significant differences relating to result. Higher mean minimum and mean average HRs were associated with LOW losers when compared to LOW winners. In low-skill players, an elevated playing intensity is likely to be caused by a combination of an opponent’s actions, and poor court-positioning strategies. However, as a lower submaximal HR response is associated with a higher level of aerobic fitness, these data may also indicate that level of aerobic conditioning is a factor in determining match-play outcomes in LOW. In direct contrast, HIGH winners achieve significantly higher minimum and average HRs than LOW winners. So in HIGH, a more intense match-play environment appears to be associated with optimal performance. Such differences suggest that training volume should be adjusted based on player level.

Hammond and Smith (2006) used an LCB in AB tennis players to develop technique and found larger mean differences in skill-test performance when using these modified balls. Also, increased rally speed, a lower ball strike and a higher proportion of net-shots are associated with an LCB (Kachel et al., 2015). More frequent net-approaches are linked with successful outcomes in AB players (Filipčič et al., 2008) and are therefore desirable. The present study revealed a moderately lower APT for LOW losers (vs. LOW winners) and this indicates that more successful outcomes are associated with an extended playing time. As an LCB is associated with longer rallies (Hammond & Smith, 2006; Cooke & Davey, 2005), an extended playing time, and therefore, elevated physiological cost and increased

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EE may result from using modified balls. However, this notion is currently speculative. The role of an LCB in facilitating more appropriate and physiologically stimulating wheelchair tennis training and match-play environments should form a consideration in future research, particularly with respect to novice player groups.