Comparisons of new body load and metabolic power average workload indices between starters and non-starters: A full-season study in professional soccer players

The aim of this study was to compare the weekly average training monotony new body load (wTM_NBL) and strain (wTS_NBL), as well as the weekly average training monotony metabolic power average (wTM_MPA) and strain (wTS_MPA) between four periods of a season (preseason, early-season, mid-season, and end-season), considering starters and non-starters. Twenty-one professional soccer players (age: 28.27 ± 3.78 years) were monitored throughout a season in the highest level of professional football Premier League in Iran. Data were captured by Global Positioning System (GPS) devices. Independent samples T-tests were applied to analyze the between-group differences for all dependent derived-GPS variables for the full season and its different periods (preseason, early-season, mid-season, and end-season). Based on the amount of time attending in match and training, players were divided into two groups (starters and non-starters) each week. The magnitude of the between-group difference revealed a very large significant greater weekly average TM_NBL (p<0.001, d = −2.42), TS_NBL (p<0.001; d = −2.74), TM_MPA (p<0.001; d =–2.79) and TS_MPA (p<0.001; d = −3.27) for starters when compared to non-starters during the early-season. The findings also revealed a very large significant difference when starters were compared to non-starters during the mid-season (TM_NBL: p<0.001, d = −2.89; TS_NBL: p<0.001, d = −2.99; TM_MPA: p<0.001, d = −3.28; and TS_MPA: p<0.001, d = −3.25) and end-season (TM_NBL: p<0.001, d = −2.89; TS_NBL: p<0.001, d = −3.07; TM_MPA: p<0.001, d = −3.16; and TS_MPA: p<0.001, d = −3.58). In summary, the results of this study revealed that starters present regularly higher values of NBL, MPA-based weekly training monotony, and training strain than non-starters. This result must be taken into account when planning weekly workloads for these groups. Specifically, starters might experience high values of external workloads because of match-related demands. Therefore, weekly adjustments in their training workload are required to reduce injury risk.