Method validated for quantifying stimuli in training tennis players

Group from the University of São Paulo analyzed 400 training sessions for competition.

By Noêmia Lopes

Agência FAPESP – A group of researchers from the School of Arts, Sciences and Humanities of the University of São Paulo (EACH/USP) has validated a rapid and safe method to assess the stimuli triggered in a tennis player’s body after training sessions for official competitions.

The technique called Rating of Perceived Exertion (RPE) for assessing a session was developed by Carl Foster at the La Crosse Campus of the University of Wisconsin in the 1990s. It consists of asking one question (How was your workout?) 30 minutes after training to determine the intensity of the physical effort on a scale of 1 to 10.

The method is already being used in sports such as soccer, swimming, rugby and canoeing and now has been validated for use in tennis by the Research Group on Biological Adaptations to Exercise at EACH.

For this purpose, the FAPESP-funded project “Quantifying training load in sport” cross-referenced data on cardiac frequency and information collected from the RPE of the session.

“We concluded that the heart’s response and the perceived exertion of the tennis player according to the RPE of the session are in optimum agreement, validating the method. In addition to being reliable, this method is easily applied, has a low cost and requires no laboratory intervention,” Marcelo Saldanha Aoki, research coordinator and professor in the USP Physical Education and Health Program, told Agência FAPESP.

Saldanha says that safely monitoring the stimuli triggered by training sessions is essential because it allows coaches and physical trainers to quantify the exercise load in order to maximize an athlete’s performance, which depends on the variation and progression of stimuli as well as on adequate recovery periods, without abandoning the necessary attention to preventing injuries and chronic fatigue brought about by excessive training (overtraining).

The cross-referencing of RPE and cardiac frequency data – measured through the use of frequency meters – included monitoring 400 training sessions conducted at tennis clubs and academies in the cities of São Paulo and Guarulhos.

In addition, athletes were monitored during a five-week pre-tournament preparation period. “After validating the RPE method for training periods, we used it to prepare for an official competition by evaluating the athletes’ hormonal, immunological and physical performance parameters,” said Saldanha.

This step involved the collection of other markers (cortisol, testosterone, IgA) in addition to RPE and cardiac frequency, again achieving agreement between the data. “In one scenario of an increased rating of perceived exertion, for example, we verified elevated levels of cortisol, the hormone related to stress. In other words, the behavior of the RPE reflected the response of some of the physiological parameters investigated,” Saldanha explained.

The findings from the first stage are being prepared for publication, and those from the second stage resulted in the article “Monitoring training loads, stress, immune-endocrine responses and performance in tennis players”, which was published in Biology of Sport.

Muscle damage induced by a tennis match

Another stage of the study conducted at EACH/USP sought to evaluate what occurs in an official tennis match in terms of muscle damage. For this, the researchers organized a simulated match and performed various measurements immediately after the competition, 24 hours later and 48 hours later.

They performed biochemical tests (measuring the blood concentration of enzymes found in skeletal muscle – a sign of muscle injury), a functionality test (if muscles have been injured, there is loss in muscle strength) and subjective tests (the sensation of muscle soreness).

The results, also published in the journal Biology of Sport in an article entitled “Muscle damage after a tennis match in young players”, indicated moderate muscle damage.

“Our study has the limit of not having investigated successive matches, five or six games in a single week, as frequently occurs in official competition. In these cases, we believe that the effect of the matches steadily increases and that muscle damage can be maximized. Furthermore, the athletes we monitored are highly trained and accustomed to heavy physical demands. We believe that beginner tennis players could suffer more muscle damage in response to a single match,” said Saldanha.

“In the future, we may expand such studies to examine scenarios with subsequent matches in an attempt to discover the magnitude of the injuries, how much they influence the tennis player’s performance and the recovery strategies that could minimize any problems detected,” stated the researcher.

The group also plans to conduct further studies regarding the distribution of the training load to test and compare various models. A first step in this direction was organizing the data collected in the RPE questionnaires during the five-week preseason in three areas: responses of 1-4 (low intensity), 4-7 (moderate intensity) and (7-10 high intensity).

“We checked to see how many sessions the athletes had in each intensity area throughout the period. We determined that, in general, most of the training sessions – 90% of them – occur at low and moderate intensity – unlike what occurs in official competitions,” said Saldanha.

In addition to the articles, the studies resulted in presentations given at the 2012 and 2013 Annual Congress of the European College of Sport Science.

“Currently, our group is also investigating methods for monitoring and quantifying the training load in other sports, such as basketball, judo and archery,” explained Saldanha. Partners in these studies are professors Alexandre Moreira of the School of Physical Education and Sports (EEFE) at USP and Aaron James Coutts at the University of Technology, Sydney and Kazunori Nosaka of Edith Cowan University, both in Australia.

The findings of these studies are part of the doctoral dissertation of Rodrigo Vitasovic Gomes, who is currently a post-doctoral researcher at EEFE/USP under the mentorship of Saldanha.