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HEART RATE VARIABILITY IN ORTHOSTATIC TEST DURING DIFFERENT TRAINING PERIODS IN ELITE SWIMMERS

Esa Hynynen1, Xavier Iglesias2, Belén Feriche3, Carmen Calderón4, Xavier Ábalos2, Jairo Vázquez2, Anna Barrero2, Lara Rodríguez2, Benjamin D. Levine, FACSM 5, Ferran A. Rodríguez, FACSM 2

1 KIHU – Research Institute for Olympic Sports, Jyväskylä, Finland, 2 INEFC, University of Barcelona, Spain, 3 FCAFyD, University of Granada, Spain, 4 Sierra Nevada High Altitude Training Center, Granada, Spain, 5 IEEM/UT Southwestern, Dallas, TX

ABSTRACT

Intense training has been shown to change the autonomic modulation of the heart in endurance athletes assessed by heart rate variability (HRV) analysis. In overtraining state HRV diminished in athletes of different sports. PURPOSE: This study investigated the effects of intensified training and tapering on HRV in elite swimmers. METHODS: Eleven elite swimmers (7 F and 4 M, age 17.9 ± 1.9 y) lived and trained for 8 weeks before national championships qualifying for European championships. This follow-up period was divided to following microcycles: preparatory general, intensified training, preparatory specific, pre-competition (tapering), and competition periods. RR-intervals were recorded every morning in supine (8 min) and orthostatic (6 min) positions with beat-by-beat heart monitors. Breathing was paced to 12 breaths/min. HRV was analyzed from the last 5-min period of both positions with FFT and autoregressive (AR) spectral power analysis. TRIMPs of every training session were calculated to estimate training. Results are presented as averages of each period and expressed in relative changes. RESULTS: Training load increased during the intensified training period (+86%, p=0.01) and progressively decreased during the pre-competition and competition. HF spectral power during supine rest increased during intensified training (+38%, P=0.03) but recovered to baseline thereafter and stayed near baseline levels during tapering and competition periods. LF/HF ratio during supine rest progressively increased from preparatory general to tapering (+58%, P=0.02) and competition periods (+66%, P=0.01). CONCLUSION: The present findings are different from previous literature of HRV in endurance athletes. Intensive training has been reported to decrease HRV acutely and a rebound was observed after a relative resting period. In this study, increase of HRV seemed to be related to positive coping with increased training stress of elite swimmers. Interpretation of LF/HF ratio has been questionable, but it has been used as an indicator of the balance of autonomic nervous system. Therefore, these findings suggest that the sympathetic activity of elite swimmers may increase during rest as an anticipatory effect of competition period. Supported by CSD (35/UPB10/10, 05/UPB32/10) and MICINN (DEP2009-09181) grants. INTRODUCTION

Elite athletes use hard training periods to induce so-called “functional overreaching” state. After an appropriate period of easier training and recovery (tapering), increased performance may be achieved. Hard training periods and sessions have been shown to affect nocturnal autonomic modulation during rest in runners (Pichot et al. 2000; Hynynen et al. 2010) and swimmers (Garet et al. 2004). Heart rate variability (HRV) was found to decrease as a stress response with a rebound of HRV after recovery. Lower HRV during wakefulness has been found in overtrained athletes in comparison to control athletes (Hynynen et al. 2008). Previously, however, HRV indices failed to show any significant changes in the follow-up of elite swimmers (Atlaoui et al. 2007). This study was done to investigate the effects of intensified training and tapering on HRV in elite swimmers.

METHODS

Eleven elite swimmers (7 females and 4 males, age 17.9 ± 1.9 years) lived and trained for 8 weeks before national championships qualifying for European championships. The swimmers followed the individual training programs set by their coaches. This follow-up period was divided to following microcycles: preparatory general, intensified training, preparatory specific, pre-competition (tapering), and competition periods. RR-intervals were recorded every morning in supine (8 min) and orthostatic (6 min) positions with Polar RS800CX heart rate monitors (Polar Electro, Kempele, Finland). Breathing was paced to 12 breaths/min (Tempo Trainer metronome, Livermore, CA). HRV was analyzed from the last 5-min period of both positions with autoregressive spectral power analysis (Kubios HRV 2.0, Kuopio, Finland). TRIMPs of every training session were calculated to estimate training load. Results are presented as averages of each period and expressed in relative changes.

RESULTS

Training load increased during the intensified training period (Fig. 1) and progressively decreased during the pre-competition and competition periods.

There were only small changes in heart rate, but large variability in HRV indices during the follow-up (Table 1). HF spectral power during supine rest increased during intensified training (Fig. 2) but recovered to baseline thereafter and stayed near baseline levels during tapering and competition periods. LF/HF ratio during supine rest progressively increased from preparatory general to tapering and competition periods (Fig. 3). HF spectral power during supine rest increased during intensified training (Fig. 2) but recovered to baseline thereafter and stayed near baseline levels during tapering and competition periods. LF/HF ratio during supine rest progressively increased from preparatory general to tapering and competition periods (Fig. 3).

Figure 1. Training load during the follow-up. Table 1. Relative change of supine and orthostatic HR and HRV from the preparatory general period.

Figure 2. Relative change of supine HFP from the preparatory general period.

Figure 3. Relative change of supine LF/HF ratio from the preparatory general period.

CONCLUSIONS The present findings are different from previous literature of HRV in endurance athletes. Intensive training has been reported to decrease HRV acutely and a rebound has been observed after a relative resting period. In this study, increase of HRV seemed to be related to positive coping with increased training stress of elite swimmers. Inter-individual variance is, however, very large. Therefore, individual follow-up is probably the best way to utilize these measurements in everyday training / coaching. Interpretation of LF/HF ratio has been questionable, but it has been used as an indicator of the balance of autonomic nervous system. Therefore, these findings suggest that the sympathetic activity of elite swimmers may increase during rest as an anticipatory effect of competition period.

REFERENCESAtlaoui D. et al. 2007. Int J Sports Med, 28: 394-400. Garet M. et al. 2004. Med Sci Sports Exerc 32: 1729-1736. Hynynen E. et al. 2008. Int J Sports Med, 29: 552-558. Hynynen E. et al. 2010. Int J Sports Med, 31: 428-432. Pichot V. et al. 2000. Med Sci Sports Exerc 32: 1729-1736.

E-mail: esa.hynynen@kihu.fi

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Pre general Intensified Pre spesific Pre comp Comp

TR

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P = 0.01

P = 0.001 P = 0.039

Pre general Intensified Pre spesific Pre comp Comp

HRsu (ms2) 0 ± 5.3 2.6 ± 10.7 1.6 ± 10.2 0.4 ± 12.1 1.0 ± 13.3

LFsu (ms2) 0 ± 50.9 34.3 ± 150.8 19.8 ± 126.6 38.8 ± 146.2 33.0 ± 99.6

HFsu (ms2) 0 ± 36.8 37.7 ± 108.4 * 4.1 ± 66.8 11.7 ± 81.5 7.5 ± 63.2

HRor (ms2) 0 ± 6.6 5.8 ± 16.9 * 5.1 ± 13.4 3.3 ± 20.9 1.1 ± 19.7

LFor (ms2) 0 ± 36.6 24.1 ± 77.5 41.7 ± 102.4 38.8 ± 66.9 55.7 ± 146.7

HFor (ms2) 0 ± 51.0 86.2 ± 246.1 76.2 ± 181.3 104.2 ± 275.3 * 117.8 ± 324.0

HR: heart rate, LF: low frequency power, HF: high frequency power, su: supine, or: orthostatic

* P < 0.05, statistical difference to pre general period

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HF

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P = 0.03

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LF

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%)

P = 0.02P = 0.01

59th Annual Meeting of the American College of Sports Medicine (ACSM), San Francisco, California, USA May 29 – June 2, 2012

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