Metabolic Power in Team Sports - Part 1: An Update

Abstract

Team sports are characterised by frequent episodes of accelerated/decelerated running. The corresponding energy cost can be estimated on the basis of the biomechanical equivalence between accelerated/decelerated running on flat terrain and constant speed running uphill/downhill. This approach allows one to: (i) estimate the time course of the instantaneous metabolic power requirement of any given player and (ii) infer therefrom the overall energy expenditure of any given time window of a soccer drill or match. In the original approach, walking and running were aggregated and energetically considered as running, even if in team sports several walking periods are interspersed among running bouts. However, since the transition speed between walking and running is known for any given incline of the terrain, we describe here an approach to identify walking episodes, thus utilising the corresponding energy cost which is smaller than in running. In addition, the new algorithm also takes into account the energy expenditure against the air resistance, for both walking and running. The new approach yields overall energy expenditure values, for a whole match,≈14% smaller than the original algorithm; moreover, it shows that the energy expenditure against the air resistance is≈2% of the total.

Metabolic Power in Team Sports - Part 2: Aerobic and Anaerobic Energy Yields

“…However, in view of the many critical observations and conflicting experimental outcomes reported by several authors [1,2,4,10], an additional series of experiments were performed in which the running speed and the corresponding instantaneous acceleration were continuously monitored by GPEXE® (Cassirame et al, in preparation). The energy cost of both running and walking episodes, as well as the metabolic power and the VO 2 time course, were then estimated by means of the same set of equations described in the accompanying paper [7]. In addition, as was the case for the preliminary set of experiments described above (▶ Fig.…”

“…Indeed, we would like to stress that although the agreement between the measured and estimated VO 2 reported above could theoretically be improved by determining the individual energy cost of transport both at constant speed and during the acceleration and deceleration phases, as well as the individual VO 2 time constants, neither option seems realistic. Therefore, we think that retaining the necessary simplified assumptions described above and in the accompanying paper [7] is the only reasonable alternative to the use of a crystal ball for assessing the energetics of team sports.…”

“…Indeed, the overall energy expenditure during a complete match (average of 497 outfield players of the Italian "Serie A" during the 2014/2015 season) is on the order of 47.5 kJ • kg − 1 (Osgnach et al, in preparation, see also ▶ Fig. 4 of the accompanying paper [7]). Hence, even assuming a blood lactate concentration at the end of the match of about 15 mM above resting (a rather extreme possibility), and taking into account the energy equivalent of lactate accumulation in blood (about 65 J • kg − 1 • mM − 1 , [6]), the corresponding net energy output can be estimated to be on the order of 1 kJ • kg − 1 , i. e., about 2 % of the total.…”

“…In the original approach, however, walking and running were aggregated and energetically considered as running, thus leading to an overestimate of the overall energy expenditure. This approach has recently been extended to take into account the different energy expenditure of the walking (versus running) episodes and the effects of air resistance on instantaneous metabolic power and overall energy expenditure (see accompanying paper [7]).…”

“…The approach described in the accompanying paper [7] has been implemented on a 18.18 Hz GPS system (GPEXE®) that can be positioned on the player's back. Hence the player's speed and instantaneous acceleration can be monitored throughout a soccer match or drill (via the Doppler effect), from which the corresponding instantaneous energy cost and metabolic power can be obtained as described in the present study.…”