End-spurt behaviour in long distance pool swimming

Abstract

Introduction: In 800 m and 1,500 m freestyle swimming an end-spurt has been observed, despite the more energetically optimal strategy being an even pace, particularly when moving a body through water. Even minor changes in speed are critical as they significantly impact energy expenditure. The ultimate goal of a competitive swimmer is to achieve completion of the race distance in the shortest possible time and beat all other competitors. The observation of end-spurt behaviour and the contradicting theoretical necessity determined the three main aims of this thesis: i) to develop an End-Spurt Indicator (ESI) to quantify and analyse end-spurt behaviour; ii) to analyse its relationship to finishing position and finishing times; and iii) to investigate the effects of an end-spurt compared to an energetically optimized pacing pattern and a race against a performance-matched opponent including its physiological underpinnings.

Method: i) To analyse the influence of distance, time point of competition, round and finishing position on end-spurt behaviour in 800 m and 1,500 m freestyle swimming from the last eight World Championships and five Olympic Games (1998–2016; including 1,433 races and 528 swimmers). The end-spurt for each race was determined by means of an ESI. Subsequently, ESI was used as a dependent variable and influences were analysed using a linear mixed model with fixed effects for distance, time point of competition, round and finishing position. ii) To analyse the association of seasonal best time, distance, and different performance levels with end-spurt behaviour in 800 m and 1,500 m pool freestyle swimming in the season 2018/2019 (including 14,930 races and 2,650 swimmers). This time ESI was used as a dependent variable and influences were analysed using a linear mixed model with fixed effects for seasonal best time, distance, and performance level amongst others. iii) To investigate the effect of forced even pacing through virtual pacing assistance and an opponent in a competitive setting on end-spurt behaviour in freestyle swimmers (including related physiological underpinnings), 27 competitive swimmers and triathletes were recruited and completed four 1,500 m freestyle trials: (i) familiarization time trial (FAM), (ii) self-paced time trial (STT), (iii) head-to-head competition time trial (CTT) and (iv) forced even pacing through virtual pacing assistance time trial (FET). Eventually, 12 swimmers met the criteria for the CTT and FET to be included in the analysis. Changes in end-spurt behaviour, finishing time and physiological parameters (lactate, cortisol, noradrenaline, heart rate) were analysed using a linear mixed model with fixed effects for trials and a random effect for swimmer identity. A separate linear model was computed for competition outcome.

Results: i) An end-spurt was evident in most swims for both race distances. The finishing position within a race significantly affected the ESI (P<.001). Specifically, when analysing finals only, ESI was significantly greater in medallists compared to non-medallists (P<.001). ii) In 800 m and 1,500 m races swimmers showed a mean ESI of 2.08 and 3.68, respectively. There was a significant association between seasonal best time and ESI, with a better seasonal best time showing a greater ESI (P<.001, f2=0.04). A significant effect on greater ESI was also observed for longer distance (P<.001, f2=0.06) and higher performance level (P<.001, f2=0.02). Elite swimmers had a mean ESI of 5.47, sub-elite swimmers of 3.74 and competitive swimmers of 2.41. iii) Swimmers demonstrated a significantly greater ESI in FET (+2,6; P<.001) and CTT (+1,4; P<.022) compared to STT. Blood lactate concentration in FET (P<.001) and CTT (P<.001) was significantly higher than in STT. Winners had a significantly greater ESI than losers in CTT (P<.005).

Conclusion: The first study used a newly developed ESI demonstrating that particularly medallists have a more pronounced end-spurt compared to non-medallists. The second study showed that a more pronounced end-spurt is associated with seasonal best time in long-distance pool swimming, higher performance level of the swimmer and longer race distance. The third study provided evidence that swimmers utilized a greater end-spurt through metabolically optimal forced even pacing by virtual pacing assistance and in a head-to-head competition due to a larger mobilization of anaerobic reserves as indicated by greater blood lactate concentrations. Winners had a significantly greater end-spurt than losers, despite similar metabolic disturbances. To summarize, swimmers use an end-spurt to a greater extent, when racing against a performance-matched competitor. Medallists and winners show a more pronounced end-spurt due to a larger mobilization of anaerobic reserve, as indicated by higher blood lactate concentrations. For future research, the sample size should be increased, and the data collection of psychological aspects is warrant.