Effects of sex differences on breath-hold diving performance

https://doi.org/10.1016/j.resp.2021.103721Get rights and content

Highlights

  • Diving response showed no sex difference between male and female breath-hold divers.

  • CO2 sensitivity showed no sex difference between male and female breath-hold divers.

  • Breath-hold diving performance and % forced vital capacity were significantly correlated.

Abstract

Purpose

The present study aimed to measure diving response, CO2 sensitivity and forced vital capacity in male and female breath-hold divers (BHDs), and to determine their effect on breath-hold diving performance.

Methods

This study included 8 non-divers (NDs, 4 males and 4 females) and 15 BHDs (7 males and 8 females). For NDs, diving response was measured during breath-holding with facial immersion, whereas for BHDs CO2 sensitivity was also measured.

Results

Compared to NDs, BHDs showed a prominent diving response. In BHDs, no statistically significant sex differences were observed in diving response and CO2 sensitivity. Furthermore, a positive correlation was found between performance and the % forced vital capacity in BHDs.

Conclusion

It was suggested that % forced vital capacity contributed more significantly to performance than diving response and CO2 sensitivity. Furthermore, the higher performance of male divers compared to female divers may be due to the % forced vital capacity rather than the diving response and CO2 sensitivity.

Introduction

Physiological factors affecting the performance of breath-hold diving have not yet been fully elucidated. Compared to non-divers (NDs), trained breath-hold divers (BHDs) can hold their breath for a long time and dive to a greater depth and distance. In addition, from the world ranking, it has been shown that the performance of male divers is higher than that of female divers (AIDA, 2020). It has been suggested that these differences in performance may be due to differences in diving response, CO2 sensitivity and forced vital capacity (Schagatay and Andersson, 1998; Delapille et al., 2001; Schagatay et al., 2012).

The diving response occurs during breath-holding with facial immersion and is characterized by decreased heart rate, increased total peripheral resistance, and decreased cardiac output (Elsner et al., 1966, Heusser et al., 2009; Lindholm and Lundgren, 2009; Fitz-Clarke, 2018). Diving response occurs by the increase in cardiac parasympathetic and muscular sympathetic activity through trigeminal nerve stimulation and respiratory arrest (Foster and Sheel, 2005; Lindholm and Lundgren, 2009). Bradycardia caused by increased cardiac parasympathetic activity reduces myocardial function, thus reducing oxygen demand. Further, the increase in total peripheral resistance caused by increased muscle sympathetic activity limits peripheral oxygen supply and distributes more blood to the heart and brain. It is believed that the diving response reduces oxygen consumption and prolongs diving duration (Schagatay and Andersson, 1998; Andersson et al., 2008; Andersson and Evaggelidis, 2009). Therefore, the more pronounced the diving response, the more oxygen will be conserved; thus, diving time may be extended.

Previous studies on NDs have reported that decreased cardiac output and increased total peripheral resistance when breath-holding with facial immersion is more pronounced in males than in females (Cherouveim et al., 2013), suggesting that diving response is related to sex difference. Therefore, one of the reasons that the performance of male divers is higher than that of female divers is considered to be a sex difference in diving response. On the other hand, it has been reported that the diving response of BHDs is more pronounced than that of NDs (Schagatay and Andersson, 1998), suggesting that the experience of training also affects the diving response. Therefore, it is necessary to examine the effect of sex difference on the diving response in BHDs.

CO2 sensitivity is the ability to sense the partial pressure of carbon dioxide in the blood, which is one of the cardiorespiratory regulatory functions. When the partial pressure of carbon dioxide in the blood is increased, it is detected mostly by the central chemoreceptors in the medulla oblongata and partially by the peripheral chemoreceptors in the carotid and aorta, which promotes contraction of the respiratory muscle. However, during breath-hold diving the glottis needs to be closed even when urging to breathe, which causes suffocation and makes it difficult to hold the breath. Therefore, it is considered that those with low CO2 sensitivity can reduce the urge to breath and extend breath-holding time.

Previous studies examining sex differences on CO2 sensitivity in NDs were lower in females than in males (MacNutt et al., 2012; Gargaglioni et al., 2019). Therefore, it is considered that females are better suited for breath-hold diving than males, but in practice, male divers perform better than female divers (AIDA, 2020). Therefore, it is unclear whether sex differences in CO2 sensitivity are observed in BHDs.

Previous studies have reported that the CO2 sensitivity of trained divers is lower than that of NDs (Davis et al., 1987; Grassi et al., 1994; Delapille et al., 2001), and with regular training, CO2 sensitivity has been suggested to be blunted. Therefore, since CO2 sensitivity is considered to be affected by training, it is necessary to confirm the role of sex difference on CO2 sensitivity in BHDs.

It is reported that there is a positive correlation between breath-hold diving performance and forced vital capacity (Schagatay et al., 2012; Fernández et al., 2017). The ability to conserve oxygen is considered important for breath-holding. Therefore, it is expected that higher forced vital capacity leads to more oxygen storage, which in turn causes a higher performance of breath-hold diving. There is a higher forced vital capacity in males compared to that in females, and it can be assumed that the performance of breath-hold diving is also higher. However, there have been no studies on the relationship between forced vital capacity and performance in male and female divers.

Therefore, the purpose of the present study was to measure diving responses, CO2 sensitivity and forced vital capacity in male and female divers, and to determine the effects they have on breath-hold diving performance.

Section snippets

Participants

This study included 15 BHDs (7 males and 8 females whose mean ± standard deviation (SD) of age, height, and weight were 38 ± 7.8 years, 167.5 ± 7.0 cm, and 59.0 ± 10.6 kg, respectively). At the time of study, all participants regularly practiced dynamic apnoea training for at least 2 h per week. A control group of 8 NDs (4 males and 4 females whose mean ± SD of age, height, and weight were 25 ± 1.7 years, 170 ± 9.5 cm, and 67.4 ± 18.9 kg, respectively) with no exercise habits were also included

Results

Physical characteristics of BHDs and NDs are presented in Table 1. Significant differences were found between BHDs and NDs in age, and %FVC (P < 0.05, respectively). Physical characteristics and performance data for male and female divers are presented in Table 2. Significant differences were found between male and female divers in height, weight, forced vital capacity, predicted vital capacity, and BMI (P < 0.05).

The absolute values of resting hemodynamic parameters in BHDs and NDs, and in

Discussion

In the present study, 15 BHDs (7 males and 8 females) and 8 NDs (4 males and 4 females) with no exercise habits were examined for their cardiovascular response during breath-holding with facial immersion. In addition, the CO2 sensitivity was also measured in BHDs. The results showed a more pronounced diving response in BHDs compared to that in NDs, but only a significant trend in the sex difference on diving response and CO2 sensitivity in BHDs were observed. In addition, in the BHDs, the

Conclusion

In BHDs with more pronounced diving response, it was suggested that % forced vital capacity contributed more significantly to performance than diving response and CO2 sensitivity. Furthermore, the higher performance of male divers than those of female divers may be due to the % forced vital capacity rather than the diving response and CO2 sensitivity.

Author contributions

Heng Peng, Takuji Kawamura and Isao Muraoka conceived and designed research; Heng Peng, Hiroshi Akiyama, Lili Chang and Risa Iwata performed experiments; Heng Peng and Takuji Kawamura analysed data; Heng Peng and Takuji Kawamura interpreted results of experiments; Heng Peng and Takuji Kawamura prepared figures; Heng Peng drafted manuscript; Heng Peng, Takuji Kawamura and Isao Muraoka edited and revised manuscript; Heng Peng, Takuji Kawamura, Hiroshi Akiyama, Lili Chang, Risa Iwata and Isao

Funding

This research did not receive any specific grant from funding agencies in the public, commercial, or not-for-profit sectors.

Declaration of Competing Interest

The authors report no declarations of interest.

Acknowledgements

The authors would like to thank the Big Blue Diving Club and the Tokyo Freediving Club for the recruitment of participants and divers for their enthusiastic participation. And the authors also would like to thank Editage (www.editage.com) for English language editing.

References (29)

  • G. Costalat et al.

    Hemodynamic adjustments during breath-holding in trained divers

    Eur. J. Appl. Physiol.

    (2013)
  • F.M. Davis et al.

    Carbon dioxide response and breath-hold times in underwater hockey players

    Undersea Biomed. Res.

    (1987)
  • P. Delapille et al.

    Ventilatory responses to hypercapnia in divers and non-divers: effects of posture and immersion

    Eur. J. Appl. Physiol.

    (2001)
  • Z. Dujic et al.

    Involuntary breathing movements improve cerebral oxygenation during apnea struggle phase in elite divers

    J. Appl. Physiol.

    (2009)
  • Cited by (0)

    View full text