Aim: The aim of this study was to assess maximal cardiac and metabolic demand imposed by in place shallow water running (SWR) and to compare such responses with those obtained during treadmil running (TMR). Methods: Twelve males, 6 trained (T) pentathletes (age: 19±1 years) and 6 untrained (UT) controls (age: 22±1 years), performed one maximal TMR test and one SWR maximal test. Heart rate (HR) and oxygen consumption (V.O2) were continuously measured in both test conditions. Results: In both groups, resting HR decreased immediately after water immersion (UT group: from 81.8±6.2 b·min-1 to 69.2±6 b·min-1; T group: from 71.7±2.1 b·min-1 to 61.7±7.7 b·min-1). In UT subjects SWR metabolic demand was comparable to that obtained during treadmill (V.O2tmr=47.9 ml·min-1±3.6; V.O2tmr=45.2 ml·min-1 ± 6.8). In contrast, during shallow SWR, T subjects obtained lower V.O2max values with respect to TMR (V.O2tmr=68.9 mL·min-1 ±5.1; V.O2TMR=57.2 mL·min-1±3.9; P<0.05). In the T group maximal HR was lower during SWR (from 191±8.1 to 177±7.1). At a given stride frequency, SWR was less demanding than treadmill in terms of V.O2 and HR responses. During SWR the metabolic adjustments were depressed more than the cardiac adjustments. Conclusion: These findings suggest that in place SWR may be a useful exercise to reduce the effects of detraining.
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