tennis

Most people would agree that tennis at top level is a tough sport. But readers might be surprised to learn that the countless breaks between rallies and sets reduce actual playing time to around 20-30% of total match time, with an exercise-to-recovery ratio in men's singles of 1:2.5.

This is one of a number of fascinating facts to emerge from a review of physiological adaptations to tennis carried out by a group of German researchers. Over the past decade, they point out, the physical and mental demands on professional tennis players have been constantly increasing, and these days players need a sophisticated and multidimensional training programme to survive on the elite circuit.

'Increasing evidence suggests,' they say,'that motor skills such as power, strength, agility, speed and explosiveness, as well as mental strength and a highly developed neuromuscular coordinating ability, are strongly correlated with tournament performance. Therefore, improvement of these attributes is indispensable to reach the international performance level.

'If these talents are not present or not sufficiently developed, cardiovascular and metabolic fitness will not be of crucial importance. On the other hand, if the athlete is not in good condition, essential characteristics in tennis such as technique, coordination, concentration and tactics cannot be brought into play
in long matches, as premature fatigue impairs virtually all tennis-specific skills.'
The adaptations to tennis and their training implications can be summarised as follows.

Cardiovascular
The mean heart rate in trained players in their twenties is 140-160 beats per minutes during singles competitions, indicating an overall intensity of 60-79% VO2max. However, heart rates can rise as high as 190-200 beats/min during long and fast rallies, while several authors have reported higher heart rates for servers than receivers - probably because of greater psychological stress - and in hot and humid climates. In terms of adaptation, well-trained tennis players have significantly lower resting heart rates and blood pressures and higher heart volumes than untrained controls.

These adaptational processes, important to meet the high demands of today's professional tennis circuit, cannot be achieved solely by match-specific, on-court tennis training, the researchers point out, and additional conditioning programmes known to improve both aerobic and anaerobic performance, such as sprint interval training, are advisable for elite players.

Crucially, though, there is a consensus that an improvement of VO2max beyond 55 (for women) and 65 (for men) mL.kg-1.min-1, which could be achieved by focusing mainly on endurance training, is not desirable in tennis since it alters muscle fibre types in such a way as to reduce strength, power, speed and explosiveness.

Energy metabolism
Regeneration of energy in well-trained players is mainly achieved aerobically, with mean lactate levels remaining fairly low. However, during long and fast rallies, energy has to be provided anaerobically, and lactate levels can double.
'In these situations,' comment the researchers,'it is important that biochemical processes for lactate removal are well developed because lactate accumulation is associated with premature fatigue and reduced accuracy of the gameÉ Although success in tennis is largely dependent on technical, tactical and coordinating motor abilities, these studies emphasise the need for a good aerobic capacity in order to maintain these abilities during hours of match playÉ Current knowledge suggests that an improvement in aerobic performance should be established by aerobic/sprint interval training.'

Hormonal system
Changes in the balance of the hormones epinephrine (reflecting mental stress) and norepinephrine (reflecting physical strain) show that tennis imposes mental as well as physical stress on players, with an epinephrine/ norepinephrine ratio after match play of 1:3.5, compared with 1:6.3 in pure endurance sports, such as cycling.

'(This) data supports the hypothesis that successful coping with mental stress may be decisive for winning or losing. It seems advisable that elite tennis players participate in special training programmes in order to increase the control over anxiety and nervousness.'

Fluid and electrolyte balance
Playing for long periods in hot environments causes sweat loss and leads to changes in fluid and electrolyte balance which may affect ionic concentration and contribute to fatigue. Even in a match lasting just two hours at 27¡C, a water loss of around 2 litres must be expected, and even small water deficits (2% body weight) have been shown to impair key elements of mental performance, thus emphasising the need for continuous and sufficient hydration.

Heat acclimatisation can be a key factor here, since players who have been training regularly in a hot environment for several weeks will sweat more readily but with reduced sodium concentrations, and are capable of maintaining a higher sweating rate for a prolonged period of time.

It is interesting to note that players who have higher levels of cardiorespiratory fitness have been shown to acclimatise more rapidly, which goes further to emphasise the importance of good conditioning.
Med Sci Sports Exercise 2001 Apr 33(4),
pp654-8

Isabel Walker