| dc.description.abstract | Since the emergence of heart rate variability (HRV) and heart rate recovery (HRR) as indicators of autonomic nervous system (ANS) activity in sport and exercise, these markers have been received with a great deal of interest and have stimulated ever-increasing research in this area. However, the use of HRV and HRR in the badminton environment, and more importantly, the possible relationships of HRV and HRR to badminton performance, have not yet been investigated. Additionally, in view of the fact that HRV and HRR are influenced by various external factors (such as muscle soreness, hydration status, sleep quality and quantity as well as pre-competition mood states), it is crucial to correct for or control these factors when evaluating these variables for use in a competitive sport setting. However, no HRV and HRR related studies have thus far considered all of these variables in their testing protocols. Lastly, HRV-related variables may also be significantly influenced by external match loads (as determined through GPS-related variables) during a badminton match.
It is in the light of this background that the main objectives of this study were: firstly, to determine if pre-match, in-match, resting and post-match HRV as well as post-match and in-match (as measured during breaks between sets) HRR can serve as significant predictors of male, elite, African, singles badminton players’ performance levels. Secondly, to determine if HRV and HRR are related to several subjective indicators of recovery status (muscle soreness, hydration status, sleep quality and quantity as well as pre-competition mood states) for different match periods in male, elite, African, singles badminton players. Thirdly, to investigate the relationship between GPS-, HR-, HRV- and HRR-related variables in male, elite, African, singles badminton players.
In order to fulfil abovemetioned objectives twenty-two, male, elite, African, singles badminton players (age: 23.3 ± 3.9 years; height: 177.1 ± 3.0 cm; mass: 83.4 ± 14.5 kg) were recruited. In total 46 national and international matches were recorded and analysed. Every day before the start of each match, players completed a recovery and hydration status questionnaire. Five to ten minutes before the start of each match, players also completed the Stellenbosch Mood Scale (STEMS). Prior to each match warm-up players were fitted with a Fix Polar Heart Rate Transmitter Belt and a MinimaxX GPS unit to record HR and court movements during matches. Before the start of each match a video camera was stationed on a tri-pod stand behind each of the courts that matches were played so that researchers were able to determine the correct duration of the matches to ensure accurate heart rate and GPS (integrated with a tri-axial accelerometer, tri-axial gyroscope and tri-axial magnetometer) analyses.
For the first objective of the study binary, forward, stepwise logistic regression analyses’ results showed that only spectral HRV indices, namely log transformed low frequency to high frequency ratio (Ln-LFnu/Ln-HFnu ratio) and peak very low frequency power (VLF power (Hz), were significantly related to group allocation of successful and less successful badminton players. Overall model fit was good and 75% of players could be classified into their original groups. Furthermore, all models had a large effect in predicting classification of players, although only the pre- and in-match models emerged as being useful.
For the second objective of the study canonical correlations for relationships between HRV-, HRR-related variables and several recovery indicators for each of the match time periods, were as follow: Rc = 0.98 (p = 0.626) for the pre-match period; Rc = 0.96 (p = 0.014) for the in-match period; Rc = 0.69 (p = 0.258) for the in-match rest periods and Rc = 0.98 (p = 0.085) for the post-match period. Canonical functions accounted for between 47.89% and 96.43% of the total variation between the two canonical variants. A strong, significant relationship was found between HRV, HRR and recovery indicators for the in-match period, but only strong, non-significant relationships were observed for pre-match and post-match periods and a low non-significant relationship for the in-match rest period. Results further revealed that log transformed normalised high frequency power (Ln-HFnu), sleep quality and mood state-related variables such as the energy index, confusion and vigour were the primary variables to contribute to relationships between the HRV-, HRR- and recovery-related variables.
For the third objective of the study results revealed a strong, non-significant canonical correlation of Rc = 0.99 (p = 0.257) between HR, HRV, HRR and GPS determined match characteristics. The total redundancy values showed that 38.47% of the variance in the nine GPS-related variables could be accounted for by the ten HR-related variables. Likewise 38.88% of the variance in the HR-related variables could be accounted for given these nine GPS-related variables. Furthermore, distance covered at a low exercise intensity, the amount of low intensity accelerations and player load were highlighted as the highest external match load-related contributors whereas Ln-HFnu power, peak HF (Hz) and Ln-LFnu/Ln-HFnu were identified as the highest internal match load-related contributors to the overall canonical correlation coefficient.
To the researchers’ knowledge, this is the first study to thoroughly investigate the ANS (through HRV and HRR) during real badminton tournaments. Most importantly the study showed that HRV and HRR can be accurately measured over different periods of competitive badminton matches. Furthermore, frequency domain-related HRV measures, when measured over the short term, appear to be related to badminton match performances and should be considered when measuring HRV in competitive sport and exercise settings. In addition, the study proved that subjective recovery indicators influence HRV and HRR measured in a competitive badminton environment and should therefore be incorporated in protocols that evaluate the ANS through HRV and HRR. Lastly, when evaluating badminton internal match loads (through HRV-related variables) coaches and sport scientists should consider and correct for the external match loads of badminton players to prevent clouded and inaccurate conclusions of ANS behaviour | en_US |
