Eccentric exercise 48 h prior to simulated diving has no effect on vascular bubble formation in rats.
OBJECTIVE
Decompression sickness (DCS) caused by vascular bubble formation is a major risk when diving. Prior studies have shown that physical exercise has a significant impact in both reducing and increasing bubble formation. There is limited knowledge about the mechanisms, but there are indications that exercise-induced muscle injury prior to diving may cause increased bubble formation. The purpose of this study was to investigate the role of exercise-induced muscle injury as a possible mechanism of bubble formation during diving.


METHODS
Muscle injury was induced by exposing female Sprague-Dawley rats (n = 30) to a single bout of eccentric exercise, 100 min intermittent, downhill (-16°) treadmill running. Forty-eight hours later, the animals were exposed to a 50-min simulated saturation dive (709 kPa) in a pressure chamber, when the degree of muscle injury and inflammation would be the most pronounced. Bubble formation after the dive was observed by ultrasonic imaging for 4 h.


RESULTS
No difference in bubble loads was found between the groups at any time despite evident muscle injury. Maximum bubble loads (bubbles cm(-2) heart cycle(-1)) were not different, exercise: 1.6 ± 3.5 SD vs control: 2.2 ± 4.1 SD, P = 0.90, n = 15 in each group.


CONCLUSIONS
Eccentric exercise performed 48 h prior to diving causes skeletal muscle injury but does not increase the amount of vascular bubbles in rats. The prevailing recommendation is that physical activity prior to diving is a risk factor of DCS. However, present and previous studies implicate that pre-dive physical activity does not increase the DCS risk.
Department of Diagnostic Imaging, St. Olavs University Hospital, Post Box 3250, 7006, Trondheim, Norway, arve.jorgensen@ntnu.no.
Arve
A
Jørgensen
Anna
A
Ekdahl
Marianne B
MB
Havnes
Ingrid
I
Eftedal
D000818:Animals; D003665:Decompression Sickness / Q000209:etiology / Q000503:physiopathology*; D004242:Diving / Q000009:adverse effects* / Q000502:physiology; D005260:Female; D005740:Gases / Q000097:blood*; D018482:Muscle, Skeletal / Q000293:injuries / Q000502:physiology*; D005082:Physical Exertion; D051381:Rats; D017207:Rats, Sprague-Dawley
D005740:Gases