title: Exercise intensity inferred from air consumption during recreational scuba diving.
abstract: BACKGROUND
  Episodic exercise is a risk factor for acute cardiac events and cardiac complications are increasingly recognized in fatalities during recreational scuba diving. What is not known is the exercise intensity involved in typical recreational diving.
  
  
  METHODS
  This study used pre- to post-dive gas cylinder pressure drop to estimate air consumption and, from that, exercise intensity during recreational dives. Dive profiles were captured electronically and divers self-reported cylinder pressure changes, perceived workload, thermal status and any problems during dives. Mean surface air consumption (SAC) rate per kg body weight and mean exercise intensity (reported in metabolic equivalents, MET multiples of assumed resting metabolic rate of 3.5 mL·kg⁻¹·min⁻¹) were then estimated. Data are reported as mean ± standard deviation.
  
  
  RESULTS
  A total of 959 recreational air dives (20 ± 9 metres' sea water maximum depth; 50 ± 12 min underwater time) by 139 divers (42 ± 10 y age; 11 ± 10 y of diving; 12% smokers; 73% male) were monitored. Problems were reported with 129/959 dives: buoyancy (45%), equalization (38%), rapid ascent (10%), vertigo (5%) and other (2%). Assuming a 10% overestimate due to cylinder cooling and uncontrolled gas loss, the estimated exercise intensity associated with monitored dives was 5 ± 1 MET. Mean ± 2SD, or 7 MET, captures the effort associated with the vast majority of dives monitored.
  
  
  CONCLUSIONS
  Our estimates suggest that uncomplicated recreational dives require moderate-intensity energy expenditure to complete, with a 7-MET capacity generally adequate. Higher levels of aerobic fitness are still strongly recommended to ensure ample reserves. Further research is needed to quantify energetic demands of recreational diving during both typical and emergent events in both experienced and less experienced divers.
authors.affiliation: Adjunct Lecturer, School of Sport Science, Exercise and Health, the University of Western Australia, Perth, Australia, Marie Curie Research Fellow, Laboratoire Optimisation des Régulations Physiologiques, Université de Bretagne Occidentale, UFR Sciences et Techniques, 6 avenue Le Gorgeu, CS 93837, Brest Cedex 3, France, Phone: +33-(0)2-9801-6235, E-mail: peter.buzzacott@uwa.edu.au.
authors.forename: Peter
authors.initials: P
authors.lastname: Buzzacott
authors.affiliation: Research Director, Divers Alert Network, Center for Hyperbaric Medicine and Environmental Physiology, Duke University Medical Center, Durham, NC, USA.
authors.forename: Neal W
authors.initials: NW
authors.lastname: Pollock
authors.affiliation: Director of the Health Promotion Evaluation Unit, School of Sport Science, Exercise and Health, the University of Western Australia, Perth, Australia.
authors.forename: Michael
authors.initials: M
authors.lastname: Rosenberg
mesh_terms: D000328:Adult; D000388:Air / Q000032:analysis*; D000399:Air Pressure; D015992:Body Mass Index; D001835:Body Weight; D004242:Diving / Q000502:physiology*; D004734:Energy Metabolism / Q000502:physiology*; D005260:Female; D006801:Humans; D008297:Male; D010101:Oxygen Consumption / Q000502:physiology; D005082:Physical Exertion / Q000502:physiology*; D010809:Physical Fitness / Q000502:physiology*; D011998:Recreation; D012623:Seawater
keywords: Aerobic capacity; diving research; exercise; fitness to dive; oxygen consumption; physiology