Differences in heart rate and lactate between classic strokes and waterpolo swimming techniques at constant pace

INTRODUCTION. Water polo is physiologically a highly demanding activity (1). During a match players often swim in different ways that do not reflect completely the classic four strokes. Hence the aim of this study was to compare heart rate and lactic acid production during classic swimming and water polo swimming techniques at constant speed in order to identify possible differences in cardiovascular energy requirement. MATERIAL AND METHODS Nine agonistic swimmers (mean±SD, age 15±1.58 years, height 163.8±4.6 cm, body mass 55.4±7.3 kg) volunteered for this study. Each participant performed 50m trials at a constant speed of 1m/s in four classic strokes crawl (CR), backstroke (BA), breaststroke (BR), butterfly (BU) and in their water polo variations (WPT): i) crawl head above the water, ii) crawl head above holding a ball, iii) crawl arm stroke - dolphin kick; iv) backstroke lower hip, v) back symmetric arm stroke - breast kick; vi) crawl arm stroke - breast kick, vii) breast arm stroke - scissor kick; viii) butterfly arm stroke - breast kick, ix) six crawl arm stroke and six backstroke arm stroke). Acoustic and visual aids were used to help swimmers keeping the pace. At the end of each trial heart rate (HR) and lactate concentration [La-] were measured through Polar X-Trainer PlusTM and Arkray-Lactate ProTM respectively. RESULTS HR: CR showed the lowest value (135.2±17.5 bpm p<0.05) compared to its WPT variations i, ii and iii; BA was significantly lower than iv (159,1±13.4 vs 169.1±15.7 bpm p<0.05); BR was significantly higher than vii (151.89±13.45 vs 136±13.57 bpm p<0.05); in BU and its variations no significant differences were found (p>0.05). [La-]: CR showed again the lowest value and it was significantly lower than its variation iii (1.76±0.25 vs 2.78±1.19 mmol/L p<0.05); BA was found significantly lower than v (2.3±0.73 vs 3.08±0.93 mmol/L p<0.05); in BR significant difference was found when compared to vii (2.26±0.62 vs 1.84±0.43 mmol/L p<0.05); no significant differences were found when comparing BU with its WPT variations (p>0.05) CONCLUSIONS Concerning our subjects (agonistic swimmers but not waterpolo players), crawl is the most economic stroke as expected (2) and shows similar values of HR and [La-] if compared to WPT vii and ix respectively (where crawl arm stroke is involved in both). The high HR we found in iv as a variation of backstroke is likely due to the low hydrodynamic body position which probably elicits more cardiovascular effort. In general it seems that swimming crawl and backstroke at a constant speed of 1m/s is less demanding in term of cardiovascular effort than some of their WPT variations, whereas it is the opposite in breaststroke and the same in butterfly.