# Pacing of Human Locomotion on Land and in Water: 1500 m Swimming vs. 5000 m Running
###### Abstract  
The study of pace strategy in different environments could help to understand its dependence on athletes' energetic limits or on sport-specific factors. The aim of this study was to analyse the pacing strategy of finalists during seven swimming and running world events held in 2021-2022. The speed of 32 swimmers every 50 m in 1500 m freestyle competitions, and the speed of 55 runners every 100 m in 5000 m track competitions, were analysed. Differences between swimming and running were statistically significant for Total Time (\(p=0.00\), ES = 1.9), Average Time of splits (\(p=0.00\), ES = 2.0), Median Time of splits (\(p=0.00\), ES = 2.0), and Maximal length of split sequences (\(p=0.00\), ES = 1.3), and non-significantly different for number of Sequences of splits (\(p=0.12\), ES = 0.5), Percentage of total splits faster than the median speed (\(p=0.08\), ES = 0.2), Percentage of splits faster than the median speed in the first half (\(p=0.16\), ES = 0.4) and Percentage of splits faster than the median speed in the second half (\(p=0.21\), ES = 0.3). In conclusion, despite similar metabolic requirements of 1500 m swimming and 5000 m running, the influence of specific environment and sport type on the pacing strategy of world level competitions seems to be supported. energy cost; endurance; training; technique; tactic; fatigue; performance; time series; mathematical modelling +
Footnote †: journal: Medical  
The velocity pattern and kinetic energy of every race are strongly dependent on the drag of the medium in which the athlete moves. The drag coefficient for swimming is thirty-fold that of running [10]. In addition to the air and water environmental differences, such as propulsion and drag, which in swimming are against the same environment, while in running propulsion and friction are against the ground and drag against the air, in pool swimming, the speed fluctuations at each stroke are small as compared to running, and drafting cannot take place [12]. As small changes in swimming velocity can cause a disproportionate rise in water resistance, a faster stroke rate will increase the amount of energy lost to the environment [13; 14; 15]. Large swimming velocity fluctuations increase the work needed to proceed at a certain velocity, both for the need to overcome inertia and drag. A \"smooth motor pattern\" is thus expected to minimize the energy cost of swimming [16]. Top-level performance in competition is a combination of variability within laps and stability between laps [17]. Hence, due to the importance of stroke technique in influencing energy cost and aerobic performance, the incorporation of the stroke rate count into the speed-time relationship analysis could be a useful criterion for controlling pacing, technical parameters, and training intensity [18; 19; 20; 21; 22; 23]. On the contrary, in running, it seems that competing at a perfectly even pace is nearly impossible [24; 25]. A notable intraindividual variability of the measurements is reported when high level endurance runners are tested to determine their aerobic ability and exercise efficiency [26]. In a prediction of 5000 m track running performance, it was shown that critical power increases when the trials are self-paced compared with constant power in laboratory conditions, thus emphasizing that gait pacing influences the speed-time relationship [27; 28]. Nonetheless, both in 1500 m running and 400 m swimming, a more conservative initial speed that allowed for increases later appears to be associated with success [11]. To understand the importance of these environmental and biomechanical differences, we hypothesised that human optimisation of energy distribution in function of exercise duration, according to the metabolic requests, could lead to specific pacing strategy backgrounds in different environments.