The physiological demands of a 16 km loaded patrol

The Royal Air Force (RAF) Regiment (Regt) is a close combat unit, their primary role is to secure the safety of an operational airfield. One of the critical tasks of the RAF Regt is a patrol, this can last approx. 4.5 hours, covering a distance of 16 km.

Purpose: To determine the physical demand of a simulated 16 km loaded patrol in RAF Regiment Regt personnel, specifically if differences occurred between the first and fifteenth km. METHODS: 26 participants from the RAF Regt performed a 16 km loaded (31.50 kg) patrol over 4 hrs 28 min. Participants received 2 x 10 min breaks at 1 hr 25 min and 3 hrs 20 min and a 20 min break at 1 hr 54 min. Rating of Perceived Exertion (RPE) was recorded at the first and second break and on completion. Walking speed was paced at 4.20 km.h 1 for the duration of the patrol. Heart rate (HR) was measured for the duration of the patrol. Oxygen consumption (V ̇O2) was measured using Douglas bag collections of 1 min at 1 km, 3 km, 5 km, 10 km and 15 km. V ̇O2 was calculated as mL.kg-1.metre-1 to allow for the variations in actual marching speed (3.80 km.h-1 to 4.92 km.h-1).

Results: No differences were reported in V ̇O2 between the first, third, fifth or tenth km in comparison with 15 km. A meaningful significant increase in V ̇O2 was observed at 10 km compared to the first km (0.24 ± 0.03 vs 0.22 ± 0.02 mL.kg-1.metre-1; p = 0.002; Cohen’s d effect size (ES) 0.60; Post hoc power (PhP) = 0.92; n = 25) and 10 km compared to the third km (0.24 ± 0.03 vs 0.22 ± 0.03 mL.kg-1.metre-1; p = 0.006; ES 0.65; PhP = 0.85; n = 19). Significantly higher (p≤0.0125) V ̇O2 was reported at 5 km compared to 3 km, however low ES and power were observed. During periods of work a linear cardiac drift was observed; mean ± SD HR of 93 ± 12.03 b.min-1 at 1 km to 110 ± 14.98 b.min-1 at 16 km. RPE remained the same for the first and second breaks (median (range); 7 (6 to 13), increasing to 8 (6 to 14) on completion of the patrol.

Conclusion: The metabolic, cardiovascular and perceived demands were low and remained low for the duration of the patrol. These data highlight that whilst the metabolic demand remained constant from the first to last km, HR increased linearly during the active element of the patrol. This suggests that HR should not be used to predict or estimate the metabolic workload of long duration activities such as the patrol.