Targeted reviews

The first review by Reid and Duffield2 examines the various pathways by which fatigue develops during match-play tennis. Specifically, the authors discuss how physiological, mechanical and psychological responses affect performance during prolonged matches. They highlight the need for research that reflects the specific demands of competitive match play in the upper echelons of the sport, and the necessity for studies that examine alterations in physiological and neuromuscular function in the context of their influence on technical, decision-making and movement skills.

During competitive match-play tennis in the heat, a measurable rise in thermal strain and the consequent exacerbated loss of body water through extensive sweating can challenge a player's physiology, perception of effort, performance and health. Given these recognised challenges, especially in tournament settings, Bergeron3 provides a thorough review of the role of hydration and thermal strain during competitive match-play tennis in the heat. The author outlines key recent findings featuring hydration-related measures and thermal strain during high-level tennis training and competition under heat stress. Issues relating to scheduling and repeated same-day matches, concerns regarding selected clinical conditions and medications, as well as caffeine, are also discussed, and the question ‘Where do we go from here?’ is candidly addressed. Finally, key recommendations of best practices to minimise exertional heat illness risk and improve player safety, well-being and on-court performance are prominently emphasised.

Irrespective of the environmental conditions, it is well established that prolonged match-play tennis and training result in the development of measureable fatigue. Accordingly, Kovacs and Baker4 examine recovery interventions and strategies to improve tennis performance by limiting the severity of fatigue and/or accelerating recovery. The review focuses on four recovery techniques commonly used in tennis to improve adaptation and performance; namely, temperature-based interventions, compressive clothing, electronic interventions and nutritional interventions.

The final targeted review by Fernandez-Fernandez et al5 addresses the topic of fitness testing for tennis players. The game has evolved from a sport in which skill was the primary pre-requisite for success to a sport that requires much greater physical, physiological and psychological attributes to effectively compete and sustain high-level performance. Accordingly, fitness testing at all levels of play has become a more prevalent and expected practice in determining a player's capacity to perform and a benchmark for gauging effectiveness of training and individual improvement. The authors describe and evaluate the various physical tests recommended and used by practitioners and sports scientists in the laboratory and field settings. Furthermore, the most appropriate tests are explained and respective age and gender normative values are provided.

Original investigations and novel findings

The original investigations highlighted in the supplement stem from an extensive study conducted at Aspetar over the period of a month with high-level European tennis players ranked from 1 to 3 by the International Tennis Federation (ITF). This comprehensive research project evaluated the influence of heat stress and hydration on match-play tennis performance in a field setting with a multidisciplinary approach.

The first article contrasts the thermal, physiological and perceptual responses associated with match-play tennis in hot and cool conditions, along with the accompanying adjustments in match characteristics.6 The results suggest that adjustments in match-play characteristics (ie, an increase in time between points leading to a decrease in effective playing time) under severe heat stress represent a behavioural strategy adopted to minimise or offset the sensation and effects of environmental conditions being rated as difficult. In the second manuscript, the time course of changes in physical performance in response to match-play tennis in the heat is assessed.7 It is noted that the physical performance parameters (ie, sprinting and jumping) associated with match-related fatigue are primarily impaired after ∼60 min of total playing time (ie, 10 min of effective play), with limited additional reductions thereafter, and that full recovery occurs within 24 h. A novel finding is that the additional increase in body core temperature incurred in the hot compared with the cool match did not exacerbate the observed reduction in physical performance.

From a neuromuscular perspective, impairments in lower limb strength and voluntary activation are highlighted in the third article in this series,8 whereas the fourth study assessed the time course of changes in rapid muscle torque production capacity.9 The results indicate that knee extensor and plantar flexor strength is reduced following match-play tennis in hot and cool conditions. Interestingly, the reduction in strength was exacerbated under heat stress in the knee extensors, and remained depressed for 24 h after match completion. The loss of strength was ascribed to a combination of central and peripheral fatigue factors in the knee extensors, and mainly to peripheral adjustments in the plantar flexors. In the knee extensors, the reduction in strength appeared to also account for a decrease in the rate of torque development, irrespective of the environmental conditions.

Article five compares the impact of match-play tennis in hot and cool conditions on changes in oxidative stress and antioxidant status.10 Intriguingly, it appears that match play in the heat does not exacerbate the development of oxidative stress, but rather significantly increases antioxidant status. This suggests that the heat stress may provide a necessary signal for the upregulation of antioxidant defence, thus dampening cellular damage.

The final investigation of the supplement examined whether an individualised hydration regimen reduces thermal, physiological and perceptual strain during match-play tennis in the heat, and minimises the alterations in physical performance and neuromuscular function postmatch and into recovery.11 The results indicate that an individualised hydration regimen and ad libitum fluid consumption allow for minimal body mass losses (<1%) to occur during match-play tennis in the heat. However, undertaking play in a well-hydrated state does appear to attenuate the early rise in thermal, physiological and perceptual strain. Conversely, repeated-sprint ability and maximal voluntary strength in the lower limbs deteriorated similarly following play under heat stress, regardless of whether competition was undertaken in a euhydrated or slightly dehydrated state, but recover within 24 h.

From the findings highlighted in this supplement issue, it is clear that competitive match-play tennis in the heat can lead to significantly greater levels of thermal strain (ie, body core temperature>39.5°C and elevated skin temperature) compared with moderate or cool conditions. This occurs despite the ability to hydrate adequately (ie, body mass losses generally ≤1%) and mitigate excessive thermal strain by employing self-pacing and on-court cooling strategies. Any measurable increase in overall thermal strain leads to a cascade of alterations in match characteristics, neuromuscular function, oxidative stress and antioxidant status, which can impact on performance acutely and potentially more so in successive matches during tournament play.

This 2014 supplement issue of the BJSM measurably extends the limited data and the current perspectives regarding competitive match-play tennis in the heat. The novel research and reviews featured in this supplement are important new contributions that significantly advance our knowledge and appreciation of the physiological responses in tennis players and the related on-court and recovery challenges they face with training and competing in hot and/or humid conditions. While these new studies have contributed to enhance our knowledge and appreciation regarding competitive match-play tennis in the heat, they, along with the targeted reviews, have also provided a number of relevant questions that remain to be explored. However, the future is bright. Particularly with the advent of new monitoring and tracking technologies, in the years ahead, tennis research in adverse environmental field conditions will be extremely interesting and likely provide many new insights and opportunities to further enhance on-court well-being, safety and performance for all players.