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Scuba diving does not affect bone mineral density or bone mineral content
Joint Bone Spine 78 (2011) 616–618
Original article
Scuba diving does not affect bone mineral density or bone mineral content Katarzyna Wesolowska a , Bozena Czarkowska-Paczek a,∗ , Jerzy Przedlacki b , Jacek Przybylski a a b
Department of Biophysics and Human Physiology, Medical University of Warsaw, Chalubinskiego Street 5, 02-004 Warsaw, Poland Chair and Department of Nephrology, Dialysotherapy and Internal Diseases, Medical University of Warsaw, Banacha Street 1a, 02-097 Warsaw, Poland
a r t i c l e
i n f o
Article history: Accepted 3 February 2011 Available online 26 March 2011 Keywords: BMD BMC Diving Bone metabolism
a b s t r a c t Objectives: Scuba diving is a very specialized, physically demanding activity. The bones of divers are subjected to stress from water pressure, from the forces generated when their muscles resist water pressure, and from weightlessness. Notably, few studies have addressed the effects of diving on bone mineral density (BMD) and bone mineral content (BMC), and the results have been controversial. The goal of the study was to assess BMD and BMC in a group of professional scuba divers. Methods: The study group (diving group [D]) included 16 male professional scuba divers who also worked as firemen. The control group included 14 firemen who did not scuba dive (non-diving group [ND]). The groups were matched by age, weight, and height. The BMD and BMC of the whole skeleton, L1–L4, total hip, and femoral neck were assessed by dual-energy X-ray absorptiometry. Results: There were no differences in BMD or in BMC in the two groups, and the BMD and BMC values were within one standard deviation in terms of Z- and T-scores. There was no correlation between total diving time (hours) and BMD in the D group. Conclusion: Scuba diving does not negatively influence bone turnover. © 2011 Société franc¸aise de rhumatologie. Published by Elsevier Masson SAS. All rights reserved.
1. Introduction Bone mineral density (BMD) and bone mineral content (BMC) clearly define the amount of mineralized bone and are associated with the risk of fracture. Some physical exercises exert beneficial and anabolic effects on BMD and BMC through both gravidity (ground reaction forces [GRF]) and joint reaction forces (JRF); however, the effect of GRF is more pronounced. [1–5]. Osteocytes are bone cells that translate mechanical loads into biochemical signals to increase bone formation. [6] In contrast, unloading is associated with a decline in BMD due to elimination of the signals that usually maintain the viability of osteocytes, leading to osteocyte apoptosis. Dying osteocytes activate osteoclasts, increasing bone resorption. At the same time, bone formation is diminished as well. The decline in BMD can reach a maximal rate of 1–1.6% per month in some parts of the skeleton [7–11]. Scuba diving is a very specialized physical activity that exposes bones to specific stresses. For example, water pressure exerts a load on bones during diving, with pressure increasing by one ATM for every 10 m of depth. This loading helps augment bone mineralization [11], and could therefore increase BMD and BMC, protecting against osteoporosis. In addition to water pressure, bones are also influenced during diving by forces that originate in contracting
∗ Corresponding author. Tel.: +48 22 628 63 34; fax: +48 22 628 78 46. E-mail address: dom [email protected] (B. Czarkowska-Paczek).
muscles. These two factors, i.e. water pressure and muscle contraction, could influence BMD and BMC in concert. On the other hand, divers experience weightlessness similar to that experienced in space or during prolonged bed rest. There is a ∼90% reduction in the diver’s effective weight, and the weight-bearing load on bones is highly reduced [12]. This could increase loss of bone minerals, leading to decreases in BMD and BMC and increasing the risk of osteoporosis. There are few published studies regarding the effects of scuba diving on BMD and BMC, and the results have been controversial. As the number of professional divers increases, it is increasingly important to determine the possible catabolic influence of diving on bone mineralization to provide optimal medical care to this group. Accordingly, the goal of this study was to assess BMD and BMC in a group of professional scuba divers. 2. Methods The study group (diving group [D]) included 16 male professional scuba divers who also worked as firemen. The control group included 14 firemen who did not scuba dive (non-diving group [ND]). In professional diving, it is easier to assess more precisely parameters of diving than in leisure, occasional diving. Standard activities of professional scuba divers-fireman in Poland include: rescuing, searching for objects under water, extraction objects from under water with the use of special equipment, helping with underwater constructing, working under ice and in water reservoirs.
1297-319X/$ – see front matter © 2011 Société franc¸aise de rhumatologie. Published by Elsevier Masson SAS. All rights reserved. doi:10.1016/j.jbspin.2011.02.005
K. Wesolowska et al. / Joint Bone Spine 78 (2011) 616–618 Table 1 Characteristics of the subjects enrolled in the study. Group ND (n = 14)
176.91 ± 5.8 85.86 ± 14.4 33.88 ± 8.5
175.79 ± 5.3 86.40 ± 11.5 36.71 ± 6.8
1,50 1,00 0,50
T
Height (cm) Weight (kg) Age (years)
1.27 ± 0.1 1.28 ± 0.1
L1–L4
Total hip
Femoral neck
1.08 ± 0.1 1.03 ± 0.1
1.08 ± 0.1 1.08 ± 0.1
0.90 ± 0.1 0.98 ± 0.2
BMD: bone mineral density; D: diving; ND: non-diving.
The Ethics Committee of the Medical University of Warsaw approved the experimental protocol. All subjects were informed about the risks and purposes of the study and provided informed written consent prior to participating in the study. The characteristics of the subjects enrolled in the study are shown in Table 1. The study group (D) and control group (ND) were matched with respect to height, weight, and age. The average number of diving years was 11.1 ± 8.9, the mean diving depth was 23.4 ± 9 m, the mean time of one dive was 45.94 ± 10.0 min, the mean time spent under water per month was 4158.61 ± 2832 min (69.31 ± 47.2 hours), and total time spent under water during last five years was 18,866 ± 14,969 min (314 ± 249 hours). The members of D and ND groups, besides diving and their activity as fireman, practice various forms of physical activity: bicycle riding, volleyball, basketball, jogging, soccer, but not in the regular manner, only in the leisure time. Eleven non-diving firemen and three diving firemen do not perform any form of leisure physical activity. The BMD and BMC of the whole skeleton, L1–L4, total hip, and femoral neck were assessed by dual-energy X-ray absorptiometry with the use of a Discovery Densitometer (Hologic, USA). The same investigator performed all measurements. 2.1. Statistical analysis Statistical analysis was performed using Statistica 6.0 software. All data are expressed as mean values ± SD. The Mann-Whitney U test was used to compare data in the two groups. Correlations are expressed using Pearson’s correlation coefficient. P values inferior to 0.05 were considered significant. 3. Results
-2,00
ND D
2957.36 ± 328.6 3035.87 ± 371.3
L1–L4
Total hip
Femoral neck
75.55 ± 9.9 74.13 ± 9.7
48.99 ± 6.7 50.19 ± 8.8
5.39 ± 0.7 5.87 ± 1.2
BMC: bone mineral content; D: diving; ND: non-diving.
total hip
femoral neck
The mean (estimated) BMD values for L1–L4, total hip, and femoral neck expressed as T-scores and Z-scores for the ND and D groups are shown in Figs. 1 and 2, respectively. The BMD and BMC in the Z- and T-score values in the ND and D groups were within a single standard deviation of each other. No correlation was observed between the total diving time (expressed in hours) and the estimated BMD of the total skeleton, L1–L4, total hip, and femoral neck in the D group (Supplementary material, Figs. S1–S4; see the supplementary material associated with this article online). 4. Discussion In the present study, we demonstrated that scuba diving does not influence BMD or BMC, and therefore, does not seem to affect bone catabolism. Mineralization of the bones of scuba divers did not differ between the ND and D groups, and the Z- and T-scores were within normal ranges. There was no correlation between the total diving time and bone mineralization in the D group. Currently, we collected 16 subjects, that could be enrolled into the investigated group, and the statistical analysis performed in the present study did not reveal neither differences nor the tendency to differences between the investigated and control groups. We cannot exclude that in the bigger groups the results could reveal some statistical significances, however, based on the current results, we assume that it is unlikely. There are only a few published studies regarding the influence of diving on BMD and BMC. Hwang et al. [11] showed that in female breath-hold divers, the BMD of the total hip and femoral neck was even greater than in a group of non-divers, although it tended to decrease more rapidly in divers in proportion to the time spent under water. The observed increase in BMD was probably caused by the load that the water exerts on the bones and by the divers’ strong muscular contractions against the resistance of the water; notably, the latter is much stronger for breath-hold divers than for scuba divers. The rapid decrease in BMD with age could be caused by lower diving depth and shorter time spent under water, which
Z
Table 3 Mean bone mineral content (BMC) values in the non-diving (ND) and diving (D) groups.
L1-L4
Fig. 1. Mean bone mineral density (BMD) values in the non-diving (ND) and diving (D) groups, expressed as T-scores.
The mean BMD and BMC values in the ND and D groups are shown in Tables 2 and 3, respectively. There were no significant differences in BMD or BMC between the groups in the whole skeleton, L1-L4, total hip, and femoral neck.
BMC (g) ± SD Total skeletal
D
-1,00 -1,50
Table 2 Mean bone mineral density (BMD) values in the non-diving (ND) and diving (D) groups.
ND D
ND
0,00 -0,50
D: diving; ND: non-diving.
BMD (g/cm2 ) ± SD Total skeletal
T
2,00
Group D (n = 16)
617
2,50 2,00 1,50 1,00 0,50 0,00 -0,50 -1,00 -1,50 -2,00
Z
ND D
L1-L4
total hip
femoral neck
Fig. 2. Mean bone mineral density (BMD) values in the non-diving (ND) and diving (D) groups, expressed as Z-scores.
618
K. Wesolowska et al. / Joint Bone Spine 78 (2011) 616–618
diminished the total load exerted on bones. In contrast to the results of this study and to those from our study, Pereira Silva et al. [12] reported that the femoral neck BMD was 4.6% lower in professional male scuba divers compared to non-divers and that BMD negatively correlated with diving time. The cause of the discrepancy could be the mean diving time: the divers studied by Pereira Silva et al. spent 31,793 ± 1959 min under water lasting the five years prior to the study, while the divers in our study spent just 18,866 ± 14,969 min. On the other hand, the breath-hold divers spent 5.2 ± 1,5 hours per day under water for 14.5 ± 5,2 days per month over 9.5 ± 3 months per year; however, the diving depth and the time spent under water for one dive must be lower than for professional scuba divers [11]. Unfortunately, we cannot compare the mean diving depth, because this parameter is not indicated in the cited articles. However, diving depth is a very important parameter because it is closely related to water pressure. Diving, both recreational as well as professional, could be accompanied by avascular bone necrosis (ABN). Its initial presentation can be painless necrosis of the joint, detectable only by MRI. ABN is the result of nitrogen and lipid emboli initiating the coagulation cascade in the microcirculation of the bone. According to the literature data, the risk of ABN is very low, both in leisure and professional diving, especially when divers strictly obey the decompression rules, and the use of MRI for routine screening is not recommended [13–15]. The bones of divers are subjected to stress from water pressure, from the forces generated when their muscles resist water pressure, and from weightlessness. The weightlessness acts in opposition to the other forces. The impact of each of these depends on the diving depth, the forces generated by muscle contractions, and the time spent under water. The total effect of diving on bones reflects the contributions of these three factors, and it is likely that the differences in BMD in groups of divers in different studies are due to differences in the diving patterns of the groups. 5. Conclusion Professional scuba diving does not negatively influence bone turnover.
Disclosure of interest The authors declare that they have no conflicts of interest concerning this article. Appendix A. Supplementary material Supplementary material (Figs. S1–S4) associated with this article can be found at http://www.sciencedirect.com, at doi:10.1016/j.jbspin.2011.02.005. References [1] Karlsson M, Nordqvist A, Karlsson K. Physical exercise increases bone mass during growth. Food Nutr Res 2008;52, doi:10.3402/fnr.v52i0.1871. [2] Stengel SV, Kemmler W, Pintag R, et al. Power training is more effective than strength training for maintaining bone mineral density in postmenopausal women. J Appl Physiol 2005;99:181–8. [3] Borer KT, Fogleman K, Gross M, et al. Walking intensity for postmenopausal bone mineral preservation and accrual. Bone 2007;41:713–21. [4] Bailey CA, Brooke-Wavell K. Optimum frequency of exercise for bone health: randomised controlled trail of high-impact unilateral intervention. Bone 2010;46:1043–9. [5] Kohrt WM, Ehsani AA, Birge Jr S. Effects of exercise involving predominantly either joint-reaction or ground-reaction forces on bone mineral density in older women. J Bone Miner Res 1997;12:1253–61. [6] Bonewald LF, Johnson ML. Osteocytes, mechanosensing and Wnt signalling. Bone 2008;42:606–15. [7] Aquirre JI, Plotkin LI, Steward SA, et al. Osteocyte apoptosis is induced by weightlessness in mice and precedes osteoclast recruitment and bone loss. J Bone Mine Res 2006;21:605–15. [8] Bloomfiled SA, Allen MR, Hogan HA, et al. Site- and compartment-specific changes in bone with hind limb unloading in mature adult rats. Bone 2002;31:149–57. [9] Spector ER, Smith SM, Sibonga JD. Skeletal effects of long-duration head-down bed rest. Aviat Space Environ Med 2009;80:A23–8. [10] Iwamoto J, Takeda T, Sato Y. Interventions to prevent bone loss in astronauts during space flight. Keio J Med 2005;54:55–9. [11] Hwang H, Bae J, Hwang S, et al. Effects of breath-hold diving on bone mineral density of woman divers. Joint Bone Spine 2006;73:419–23. [12] Pereira Silva JA, Costa Dias F, Fonseca JE, et al. Low bone mineral density in professional scuba divers. Clin Rheumatol 2004;23:19–20. [13] Laden GDM, Grout P. Aseptic bone necrosis in an amateur scuba diver. Br J Sports Med 2004:e19. [14] Uzun G, Toklu AS, Yidiz S, et al. Dysbaric osteonecrosis screening in Turkish Navy divers. Aviat Space Environ Med 2008;79:44–6. [15] Kenney IJ, Sonksen C. Dysbaric osteonecrosis in recreational divers: a study using magnetic resonance imaging. Undersea Hyperb Med 2010;37:281–8.
Original article
Scuba diving does not affect bone mineral density or bone mineral content Katarzyna Wesolowska a , Bozena Czarkowska-Paczek a,∗ , Jerzy Przedlacki b , Jacek Przybylski a a b
Department of Biophysics and Human Physiology, Medical University of Warsaw, Chalubinskiego Street 5, 02-004 Warsaw, Poland Chair and Department of Nephrology, Dialysotherapy and Internal Diseases, Medical University of Warsaw, Banacha Street 1a, 02-097 Warsaw, Poland
a r t i c l e
i n f o
Article history: Accepted 3 February 2011 Available online 26 March 2011 Keywords: BMD BMC Diving Bone metabolism
a b s t r a c t Objectives: Scuba diving is a very specialized, physically demanding activity. The bones of divers are subjected to stress from water pressure, from the forces generated when their muscles resist water pressure, and from weightlessness. Notably, few studies have addressed the effects of diving on bone mineral density (BMD) and bone mineral content (BMC), and the results have been controversial. The goal of the study was to assess BMD and BMC in a group of professional scuba divers. Methods: The study group (diving group [D]) included 16 male professional scuba divers who also worked as firemen. The control group included 14 firemen who did not scuba dive (non-diving group [ND]). The groups were matched by age, weight, and height. The BMD and BMC of the whole skeleton, L1–L4, total hip, and femoral neck were assessed by dual-energy X-ray absorptiometry. Results: There were no differences in BMD or in BMC in the two groups, and the BMD and BMC values were within one standard deviation in terms of Z- and T-scores. There was no correlation between total diving time (hours) and BMD in the D group. Conclusion: Scuba diving does not negatively influence bone turnover. © 2011 Société franc¸aise de rhumatologie. Published by Elsevier Masson SAS. All rights reserved.
1. Introduction Bone mineral density (BMD) and bone mineral content (BMC) clearly define the amount of mineralized bone and are associated with the risk of fracture. Some physical exercises exert beneficial and anabolic effects on BMD and BMC through both gravidity (ground reaction forces [GRF]) and joint reaction forces (JRF); however, the effect of GRF is more pronounced. [1–5]. Osteocytes are bone cells that translate mechanical loads into biochemical signals to increase bone formation. [6] In contrast, unloading is associated with a decline in BMD due to elimination of the signals that usually maintain the viability of osteocytes, leading to osteocyte apoptosis. Dying osteocytes activate osteoclasts, increasing bone resorption. At the same time, bone formation is diminished as well. The decline in BMD can reach a maximal rate of 1–1.6% per month in some parts of the skeleton [7–11]. Scuba diving is a very specialized physical activity that exposes bones to specific stresses. For example, water pressure exerts a load on bones during diving, with pressure increasing by one ATM for every 10 m of depth. This loading helps augment bone mineralization [11], and could therefore increase BMD and BMC, protecting against osteoporosis. In addition to water pressure, bones are also influenced during diving by forces that originate in contracting
∗ Corresponding author. Tel.: +48 22 628 63 34; fax: +48 22 628 78 46. E-mail address: dom [email protected] (B. Czarkowska-Paczek).
muscles. These two factors, i.e. water pressure and muscle contraction, could influence BMD and BMC in concert. On the other hand, divers experience weightlessness similar to that experienced in space or during prolonged bed rest. There is a ∼90% reduction in the diver’s effective weight, and the weight-bearing load on bones is highly reduced [12]. This could increase loss of bone minerals, leading to decreases in BMD and BMC and increasing the risk of osteoporosis. There are few published studies regarding the effects of scuba diving on BMD and BMC, and the results have been controversial. As the number of professional divers increases, it is increasingly important to determine the possible catabolic influence of diving on bone mineralization to provide optimal medical care to this group. Accordingly, the goal of this study was to assess BMD and BMC in a group of professional scuba divers. 2. Methods The study group (diving group [D]) included 16 male professional scuba divers who also worked as firemen. The control group included 14 firemen who did not scuba dive (non-diving group [ND]). In professional diving, it is easier to assess more precisely parameters of diving than in leisure, occasional diving. Standard activities of professional scuba divers-fireman in Poland include: rescuing, searching for objects under water, extraction objects from under water with the use of special equipment, helping with underwater constructing, working under ice and in water reservoirs.
1297-319X/$ – see front matter © 2011 Société franc¸aise de rhumatologie. Published by Elsevier Masson SAS. All rights reserved. doi:10.1016/j.jbspin.2011.02.005
K. Wesolowska et al. / Joint Bone Spine 78 (2011) 616–618 Table 1 Characteristics of the subjects enrolled in the study. Group ND (n = 14)
176.91 ± 5.8 85.86 ± 14.4 33.88 ± 8.5
175.79 ± 5.3 86.40 ± 11.5 36.71 ± 6.8
1,50 1,00 0,50
T
Height (cm) Weight (kg) Age (years)
1.27 ± 0.1 1.28 ± 0.1
L1–L4
Total hip
Femoral neck
1.08 ± 0.1 1.03 ± 0.1
1.08 ± 0.1 1.08 ± 0.1
0.90 ± 0.1 0.98 ± 0.2
BMD: bone mineral density; D: diving; ND: non-diving.
The Ethics Committee of the Medical University of Warsaw approved the experimental protocol. All subjects were informed about the risks and purposes of the study and provided informed written consent prior to participating in the study. The characteristics of the subjects enrolled in the study are shown in Table 1. The study group (D) and control group (ND) were matched with respect to height, weight, and age. The average number of diving years was 11.1 ± 8.9, the mean diving depth was 23.4 ± 9 m, the mean time of one dive was 45.94 ± 10.0 min, the mean time spent under water per month was 4158.61 ± 2832 min (69.31 ± 47.2 hours), and total time spent under water during last five years was 18,866 ± 14,969 min (314 ± 249 hours). The members of D and ND groups, besides diving and their activity as fireman, practice various forms of physical activity: bicycle riding, volleyball, basketball, jogging, soccer, but not in the regular manner, only in the leisure time. Eleven non-diving firemen and three diving firemen do not perform any form of leisure physical activity. The BMD and BMC of the whole skeleton, L1–L4, total hip, and femoral neck were assessed by dual-energy X-ray absorptiometry with the use of a Discovery Densitometer (Hologic, USA). The same investigator performed all measurements. 2.1. Statistical analysis Statistical analysis was performed using Statistica 6.0 software. All data are expressed as mean values ± SD. The Mann-Whitney U test was used to compare data in the two groups. Correlations are expressed using Pearson’s correlation coefficient. P values inferior to 0.05 were considered significant. 3. Results
-2,00
ND D
2957.36 ± 328.6 3035.87 ± 371.3
L1–L4
Total hip
Femoral neck
75.55 ± 9.9 74.13 ± 9.7
48.99 ± 6.7 50.19 ± 8.8
5.39 ± 0.7 5.87 ± 1.2
BMC: bone mineral content; D: diving; ND: non-diving.
total hip
femoral neck
The mean (estimated) BMD values for L1–L4, total hip, and femoral neck expressed as T-scores and Z-scores for the ND and D groups are shown in Figs. 1 and 2, respectively. The BMD and BMC in the Z- and T-score values in the ND and D groups were within a single standard deviation of each other. No correlation was observed between the total diving time (expressed in hours) and the estimated BMD of the total skeleton, L1–L4, total hip, and femoral neck in the D group (Supplementary material, Figs. S1–S4; see the supplementary material associated with this article online). 4. Discussion In the present study, we demonstrated that scuba diving does not influence BMD or BMC, and therefore, does not seem to affect bone catabolism. Mineralization of the bones of scuba divers did not differ between the ND and D groups, and the Z- and T-scores were within normal ranges. There was no correlation between the total diving time and bone mineralization in the D group. Currently, we collected 16 subjects, that could be enrolled into the investigated group, and the statistical analysis performed in the present study did not reveal neither differences nor the tendency to differences between the investigated and control groups. We cannot exclude that in the bigger groups the results could reveal some statistical significances, however, based on the current results, we assume that it is unlikely. There are only a few published studies regarding the influence of diving on BMD and BMC. Hwang et al. [11] showed that in female breath-hold divers, the BMD of the total hip and femoral neck was even greater than in a group of non-divers, although it tended to decrease more rapidly in divers in proportion to the time spent under water. The observed increase in BMD was probably caused by the load that the water exerts on the bones and by the divers’ strong muscular contractions against the resistance of the water; notably, the latter is much stronger for breath-hold divers than for scuba divers. The rapid decrease in BMD with age could be caused by lower diving depth and shorter time spent under water, which
Z
Table 3 Mean bone mineral content (BMC) values in the non-diving (ND) and diving (D) groups.
L1-L4
Fig. 1. Mean bone mineral density (BMD) values in the non-diving (ND) and diving (D) groups, expressed as T-scores.
The mean BMD and BMC values in the ND and D groups are shown in Tables 2 and 3, respectively. There were no significant differences in BMD or BMC between the groups in the whole skeleton, L1-L4, total hip, and femoral neck.
BMC (g) ± SD Total skeletal
D
-1,00 -1,50
Table 2 Mean bone mineral density (BMD) values in the non-diving (ND) and diving (D) groups.
ND D
ND
0,00 -0,50
D: diving; ND: non-diving.
BMD (g/cm2 ) ± SD Total skeletal
T
2,00
Group D (n = 16)
617
2,50 2,00 1,50 1,00 0,50 0,00 -0,50 -1,00 -1,50 -2,00
Z
ND D
L1-L4
total hip
femoral neck
Fig. 2. Mean bone mineral density (BMD) values in the non-diving (ND) and diving (D) groups, expressed as Z-scores.
618
K. Wesolowska et al. / Joint Bone Spine 78 (2011) 616–618
diminished the total load exerted on bones. In contrast to the results of this study and to those from our study, Pereira Silva et al. [12] reported that the femoral neck BMD was 4.6% lower in professional male scuba divers compared to non-divers and that BMD negatively correlated with diving time. The cause of the discrepancy could be the mean diving time: the divers studied by Pereira Silva et al. spent 31,793 ± 1959 min under water lasting the five years prior to the study, while the divers in our study spent just 18,866 ± 14,969 min. On the other hand, the breath-hold divers spent 5.2 ± 1,5 hours per day under water for 14.5 ± 5,2 days per month over 9.5 ± 3 months per year; however, the diving depth and the time spent under water for one dive must be lower than for professional scuba divers [11]. Unfortunately, we cannot compare the mean diving depth, because this parameter is not indicated in the cited articles. However, diving depth is a very important parameter because it is closely related to water pressure. Diving, both recreational as well as professional, could be accompanied by avascular bone necrosis (ABN). Its initial presentation can be painless necrosis of the joint, detectable only by MRI. ABN is the result of nitrogen and lipid emboli initiating the coagulation cascade in the microcirculation of the bone. According to the literature data, the risk of ABN is very low, both in leisure and professional diving, especially when divers strictly obey the decompression rules, and the use of MRI for routine screening is not recommended [13–15]. The bones of divers are subjected to stress from water pressure, from the forces generated when their muscles resist water pressure, and from weightlessness. The weightlessness acts in opposition to the other forces. The impact of each of these depends on the diving depth, the forces generated by muscle contractions, and the time spent under water. The total effect of diving on bones reflects the contributions of these three factors, and it is likely that the differences in BMD in groups of divers in different studies are due to differences in the diving patterns of the groups. 5. Conclusion Professional scuba diving does not negatively influence bone turnover.
Disclosure of interest The authors declare that they have no conflicts of interest concerning this article. Appendix A. Supplementary material Supplementary material (Figs. S1–S4) associated with this article can be found at http://www.sciencedirect.com, at doi:10.1016/j.jbspin.2011.02.005. References [1] Karlsson M, Nordqvist A, Karlsson K. Physical exercise increases bone mass during growth. Food Nutr Res 2008;52, doi:10.3402/fnr.v52i0.1871. [2] Stengel SV, Kemmler W, Pintag R, et al. Power training is more effective than strength training for maintaining bone mineral density in postmenopausal women. J Appl Physiol 2005;99:181–8. [3] Borer KT, Fogleman K, Gross M, et al. Walking intensity for postmenopausal bone mineral preservation and accrual. Bone 2007;41:713–21. [4] Bailey CA, Brooke-Wavell K. Optimum frequency of exercise for bone health: randomised controlled trail of high-impact unilateral intervention. Bone 2010;46:1043–9. [5] Kohrt WM, Ehsani AA, Birge Jr S. Effects of exercise involving predominantly either joint-reaction or ground-reaction forces on bone mineral density in older women. J Bone Miner Res 1997;12:1253–61. [6] Bonewald LF, Johnson ML. Osteocytes, mechanosensing and Wnt signalling. Bone 2008;42:606–15. [7] Aquirre JI, Plotkin LI, Steward SA, et al. Osteocyte apoptosis is induced by weightlessness in mice and precedes osteoclast recruitment and bone loss. J Bone Mine Res 2006;21:605–15. [8] Bloomfiled SA, Allen MR, Hogan HA, et al. Site- and compartment-specific changes in bone with hind limb unloading in mature adult rats. Bone 2002;31:149–57. [9] Spector ER, Smith SM, Sibonga JD. Skeletal effects of long-duration head-down bed rest. Aviat Space Environ Med 2009;80:A23–8. [10] Iwamoto J, Takeda T, Sato Y. Interventions to prevent bone loss in astronauts during space flight. Keio J Med 2005;54:55–9. [11] Hwang H, Bae J, Hwang S, et al. Effects of breath-hold diving on bone mineral density of woman divers. Joint Bone Spine 2006;73:419–23. [12] Pereira Silva JA, Costa Dias F, Fonseca JE, et al. Low bone mineral density in professional scuba divers. Clin Rheumatol 2004;23:19–20. [13] Laden GDM, Grout P. Aseptic bone necrosis in an amateur scuba diver. Br J Sports Med 2004:e19. [14] Uzun G, Toklu AS, Yidiz S, et al. Dysbaric osteonecrosis screening in Turkish Navy divers. Aviat Space Environ Med 2008;79:44–6. [15] Kenney IJ, Sonksen C. Dysbaric osteonecrosis in recreational divers: a study using magnetic resonance imaging. Undersea Hyperb Med 2010;37:281–8.