Abstract
Humans share with seals the ability to contract the spleen and increase circulating hematocrit, which may improve apneic performance by enhancing gas storage. Seals have large spleens and while human spleen size is small in comparison, it shows great individual variation. Unlike many marine mammals, human divers rely to a great extent on lung oxygen stores, but the impact of lung volume on competitive apnea performance has never been determined. We studied if spleen- and lung size correlated with performance in elite apnea divers. Volunteers were 14 male apnea world championship participants, with a mean (SE) of 5.8 (1.2) years of previous apnea training. Spleen volume was calculated from spleen length, width, and thickness measured via ultrasound during rest, and vital capacity via spirometry. Accumulated competition scores from dives of maximal depth, time, and distance were compared to anthropometric measurements and training data. Mean (SE) diving performance was 75 (4) m for constant weight depth, 5 min 53 (39) s for static apnea and 139 (13) m for dynamic apnea distance. Subjects’ mean height was 184 (2) cm, weight 82 (3) kg, vital capacity (VC) 7.3 (0.3) L and spleen volume 336 (32) mL. Spleen volume did not correlate with subject height or weight, but was positively correlated with competition score (r = 0.57; P < 0.05). Total competition score was also positively correlated with VC (r = 0.54; P < 0.05). The three highest scoring divers had the greatest spleen volumes, averaging 538 (53) mL, while the three lowest-scoring divers had a volume of 270 (71) mL (P < 0.01). VC was also greater in the high-scorers, at 7.9 (0.36) L as compared to 6.7 (0.19) L in the low scorers (P < 0.01). Spleen volume was reduced to half after 2 min of apnea in the highest scoring divers, and the estimated resting apnea time gain from the difference between high and low scorers was 15 s for spleen volume and 60 s for VC. We conclude that both spleen- and lung volume predict apnea performance in elite divers.
Highlights
Humans have the ability to contract the spleen during diving and increase circulating hematocrit (Hurford et al, 1990) which seems to prolong apneas when performed in series (Schagatay et al, 2001)
A significant correlation was found between accumulated competition score and both spleen volume and lung volume, despite the relatively small number of subjects investigated in this study, suggesting that both these factors may predict competitive apneic performance
Whether our findings indicate training-stimulated growth or reflects individual predisposition can not be determined in this study, but the spleen volume of the three most successful divers is clearly in the upper www.frontiersin.org range of that observed in healthy humans, which may indicate this possibility
Summary
Humans have the ability to contract the spleen during diving and increase circulating hematocrit (Hurford et al, 1990) which seems to prolong apneas when performed in series (Schagatay et al, 2001). This response is well known in seals, where spleen size varies greatly between species and in some deep divers like the Weddell seal it is exceptionally large with the ability to store 2/3 of the body’s erythrocytes during rest (Qvist et al, 1986). Spleen size shows great individual variation in humans (Prassopoulos et al, 1997), and its ability to contract appears to vary between individuals (Schagatay et al, 2005) but it has never been determined whether these factors correlate with individual apneic diving ability
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
