Evidence of a non-linear dose-response relationship between training load and stress markers in elite female futsal players.

Author:Milanez, Vinicius F.
Position::Research article - Report


Monitoring training loads (TL) in combination with psychophysiological responses has been suggested as necessary to prevent overreaching and overtraining. The session-rating of perceived exertion (i.e. session-RPE) has been demonstrated to be a simple and practical method for quantifying internal TL in team sports (Alexiou and Coutts, 2008; Foster et al., 2001; Impellizzeri et al., 2004). A way to evaluate the impact of physiological stress on immunity is to analyze the salivary secretory immunoglobulin A (SIgA) level, which is considered to be a marker inversely related to the risk of developing upper respiratory infection (URI) symptoms in athletes (Fahlman and Engels, 2005; Walsh et al., 2011). Some studies have shown that low SIgA levels may reduce resistance to infections and also increase the risk of impaired performance in competitions, which is often regarded as a higher than normal psychophysiological stress level (Gleeson et al., 1999; Tsai et al., 2011).

Additionally, "Daily Analysis of Life Demands in Athletes Questionnaire" (DALDA) (Coutts et al., 2007b; Neville et al., 2008) and the "Wisconsin Upper Respiratory Symptom Survey-21" (WURSS-21) questionnaire (Moreira et al., 2011a; Rushall, 1990) have previously been used as simple tools to monitor the immune response and prevent excessive psychophysiological stress that may negatively alter athletes' health and performance. In this regard, Coutts et al. (2007b) and Moreira et al. (2011a) have shown that the DALDA questionnaire is a sensitive tool for monitoring individual athletes' responses to internal TL. Furthermore, significant relationships between increased TL (Foster, 1998) and volume of exercise (Gleeson et al., 2013) with symptoms of URI have been also documented. However, some authors presented inconsistent results between the relationship of TL, stress symptoms, SIgA levels, and URI (Cox et al., 2007; Fahlman and Engels, 2005; Gleeson et al., 2000; Leicht et al., 2012; Neville et al., 2008).

To date, the relationship between session-RPE and corresponding psychophysiological responses has not been sufficiently addressed, especially in female athletes. The clarification of this relationship is important because it is not known if typical TL carried out by professional female team sports players can induce alterations in stress symptoms, SIgA levels, and URI incidence in the same way as their male counterparts. For instance, female athletes may experience more stress in similar TL than male athletes (di Fronso et al., 2013; Kellmann et al., 2001), and consequently they may require special attention from coaches and physical trainers in order to manage TL appropriately on a daily basis.

Thus, the objectives of this study were twofold: 1) to describe typical TL experienced by a professional female futsal team during the 5 weeks before the main national competition by means of the session-RPE method and; 2) to verify the relationship between TL, stress symptoms, SIgA levels and symptoms of URI. We hypothesized that periods of intensified TL would increase stress symptoms, decrease SIgA levels with a corresponding increase in the susceptibility to URI.



Thirteen top-level professional female futsal players (mean and SD; age: 22.1 [+ or -] 4.2 years; body mass: 60.7 [+ or -] 5.9 kg; height: 1.65 [+ or -] 0.5 m and BMI 22.3 [+ or -] 1.4 kg x [m.sup.-2]) who were second place in the Brazilian National League in 2009 were enrolled in the study. The players had a training experienced of 4-5 years. They signed a written informed consent form. The study was approved by the Institutional Ethics Committee.


Firstly, the players performed an incremental running test to determine the ventilatory threshold (VT), respiratory compensation point (RCP), and maximal oxygen consumption (VO2max). The players were also submitted to an oral examination for detection of clinical signs of periodontal disease, active caries or mucosal lesions. The follow-up study initiated after the State championship played in the first half of the year and was comprised of 5 weeks during the preparation period for a national main championship in Brazil, in the second half of the year. The TL of the players was monitored on a daily basis by means of the session-RPE method for 45 training sessions. Stress symptoms as assessed by DALDA, symptoms of URI as assessed by WURSS-21 and salivary SIgA levels were measured in the afternoon, prior to the last training session of each week. Subsequently, the relationships between TL and training strain (independent variable) with stress symptoms, SIgA, and symptoms of URI responses (dependent variables) were determined to ascertain possible associations.


Incremental test

The incremental test on the treadmill (Super ATL--Inbrasport[R], Brazil) started at 6 km [h.sup.-1]. The inclination was kept constant at 1[degrees]%, and the speed was increased by 1 km x [h.sup.-1] every minute until voluntary exhaustion. Heart rate (HR) was recorded with a short-range telemetry system (RS800, Polar Electro Oy, Finland). Pulmonary gas exchange was averaged every 20-s using a metabolic cart (Metalyzer 3B, CPX System, Germany). The [O.sub.2] and C[O.sub.2] analyzers were calibrated using gases of known concentration and the volume signal was calibrated with a 3 L syringe. The VT and RCP were determined as suggested by Lucia et al. (2003). All the players met at least two of the following criteria at exhaustion to validate the V[O.sub.2max] attainment: a plateau in oxygen consumption, RER values above 1.10, and HR within 5 bpm of age-predicted maximum (Billat et al., 1996).

Training program

The designated training sessions consisted of resistance training (RT), technical-tactical training (TT), and physical training (PT) over a 5 week period. In the typical training sessions (1-3 weeks), RT consisted of 3 sets of 15 reps at 70% of repetition maximum (RM) with rest intervals of 45 s, carried out 4 times a week with a mean duration of ~30-40 minutes per day. The PT was developed together with TT on court, 5 times a week with a mean duration of ~80-120 min per day. In the week 4, RT was decreased to 2 times a week while no RT sessions were performed in the week 5. During the last two weeks, volume and intensity of both TT and PT were maintained relatively constant.

Quantification of internal training load

The internal TL was computed by using the session-RPE method. Approximately 30 minutes following the completion of every training session, the players were asked to rate the intensity of the whole session by means of a modified 10-point RPE scale (Foster et al., 2001). This value of RPE was multiplied by the total duration of the training session. All the players were previously familiarized with the use of the RPE scale. The session-RPE loads were recorded as total weekly and daily average units. Concurrently with the session-RPE, the "strain" and "monotony" were calculated weekly in accordance with Foster (1998). The monotony was calculated weekly by dividing the weekly mean TL by the standard deviation, while training strain was calculated as the overall weekly TL multiplied by monotony.

Stress symptoms

The DALDA (Rushall, 1990) was administered to measure weekly stress sources/symptoms. The DALDA questionnaire is divided into two parts, namely Part A and Part B, which represent the sources of life stress and symptoms of stress, respectively. Each subject was required to complete the DALDA prior the last training session of each week at the same time of the day. The players marked every question as being either "worse than the normal", "normal" or "better than the normal". This questionnaire was filled out at the end of every week of training and number of responses labeled as "worse than normal" was retained for analysis (Moreira et al., 2011b). We considered for analysis only part B of the questionnaire, in accordance with Coutts et al. (2007c).

Salivary secretory immunoglobulin A (SIgA)

Enzyme-linked immunosorbent assay (ELISA) was used for analyses of SIgA levels. The samples were collected at rest. The baseline...

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