The physiological demand of pulling a rescue sled across the mud and the impact experience has on this task

Background: To establish a Physical Employment Standard for tasks with high physical demands, it is important to determine the physiological requirements. One such task for the UK Coastguard is mud rescue.
Objective: To quantify the physiological demand of pulling a rescue sled across estuary mud, and determine whether rescuer experience has an impact on the physiological demand of this task. 
Methods: Forty participants walked 150 m in 3 minutes across estuary mud. Following 3 minute rest, they walked 150 m pulling a rescue sled (61 kg) in pairs (based on experience).
Results: Experienced rescuers had a total oxygen consumption approximately 24% lower than those inexperienced in the task. Relative oxygen consumption (V ̇O2) was significantly (p<0.05) greater in the non-experienced (mean [SD]; 42.90 [6.55] mL.kg-1.min-1) compared to the experienced group (32.85 [5.79] mL.kg-1.min-1) when controlled for pace. Required V ̇O2 for various speeds were predicted based on non-experienced participants and assessed for agreement. LoA (95%) mean ± difference was 0.0003 ± 3.48 mL.kg-1.min-1, with a CV of 2.30 %. 
Conclusions: For tasks that require a high relative V ̇O2, such as mud rescue, the minimum level of fitness at entry should be based upon the metabolic demands measured on those who are inexperienced.