2007, Piran, Slovenia

Environmental Ergonomics XII
Igor B. Mekjavic, Stelios N. Kounalakis & Nigel A.S. Taylor (Eds.), © BIOMED, Ljubljana 2007
74
A NOVEL METHOD TO MEASURE OXYGEN CONSUMPTION
DURING UNDERWATER FINNING
Carol House 1 , Heather Lunt 1 , Crawford Foster 1 , Jim House 1 and Igor Mekjavic 2
1 Institute of Naval Medicine, Portsmouth, UK; 2 Josef Stefan Institute, Slovenia
Contact person: Carol House hsosurv@inm.mod.uk
INTRODUCTION
The UK military endorses the rationale that personnel should always possess
sufficient physical fitness to meet the demands of their operational role. Accordingly
personnel are required to pass a fitness test before beginning training as a military
diver. This consists of a timed 1.5 mile (2.4 km) run (to be completed in 10.5 mins by
Navy and 9.5 mins by Army personnel), sit-ups (minimum of 40 in one minute), pullups
(minimum of 8) and dips (minimum of 16). However, to be legally defensible and
scientifically valid the test should be based upon objective measures that reflect
critical or essential demands of the job. No recognised rationale for the current diving
fitness test is available. Work by the US military indicates that their physical
screening test for divers, which is similar to that used by the UK military is a poor
predictor of capability to complete military diving tasks and hence has limited utility
for physical selection purposes (Marcinik et al, 1995).
Swimming underwater using fins and a self contained underwater breathing apparatus
(SCUBA) is fundamental to the work of a military diver. Discussions with
experienced military divers established a universal demand based upon searching the
underside of ships for damage or ordnance. To complete this task divers must be able
to fin and make progress against a tidal stream of 1.0 kts for 30 mins. The aim of this
study was to quantify the aerobic demands of finning underwater in static water at 1.1
kts which was intended to simulate making headway in a tidal stream of 1.0 kts; and
to determine whether a running test would be a suitable predictor of finning
capability.
METHOD
Eight experienced military divers volunteered for the study and their informed consent
was gained in accordance with the Declaration of Helsinki. The subjects undertook
four dives, two in a lake and two in an immersion tank, all on separate days. For all
the dives the subjects used Swimmer’s Air Breathing Apparatus MoD 1 (SABA) with
full face mask, which is an open circuit SCUBA with a main cylinder and bailout
cylinder each filled with compressed air. The subjects wore a dry suit and undersuit,
and military issue fins. Before each dive, euhydration was assessed by measuring the
specific gravity (SG) of urine samples. Any subject with an SG > 1.015 was required
to drink water until the SG of his urine fell to this level. The mean (SD) temperature
of the water in the lake was 6.0 (0.4)°C and in the immersion tank was 6.3 (1.7)°C.
For the dives in the lake the subjects (in pairs) finned at a depth of 3 metres. The
subjects were paced (by the diving boat which used GPS) to fin at 0.7 kts and
following a short rest period at 1.1 kts, each for 10 minutes. (It was intended that the
divers would also fin for 10 mins at 1.5 kts, but this was not possible because they
could not fin at this speed). The divers followed the longitudinal jack line down the
lake which ensured finning in a straight line. The velocity of each diver was
confirmed by recording the actual time taken to complete the distance. Heart rate was