Comparisons of accelerometer variables acute, chronic and acute/chronic workload ratio between starters and non-starters: A full-season study in professional soccer players

Summary Objectives Monitoring training workload via accelerometer-derived microsensors has been used extensively in professional team sports. However, a comparison of training states between starters and non-starts professional players in an entire season has not been fully investigated. The aim of this study was to examine to compare the workload parameters (i.e. the acute, chronic, acute/chronic workload ratio, metabolic power average, acceleration, and deceleration) between starters and non-starters players in four different periods of professional football season. Equipment and methods This study followed a retrospective and longitudinal design. Twenty-one Iranian professional soccer players (age, 28.27 ± 3.78 years; height, 181.23 ± 7.08 cm; body mass, 74.45 ± 7.72 kg) completed an entire season in 2018–2019 and participated in this study. A wearable device with a tri-axial accelerometer (SPI HPU, GPSports systems) was used to monitor the locomotor profile during training sessions and matches over a forty-eight-weeks season (pre-season = week 1–5; early-season = week 6–19; mid-season = week 20–34; end-season = week 35–48). Body load was used to calculate acute (7 days), chronic workload (previous 3 weeks), and acute/chronic workload ratio. The metabolic power average, acceleration, and deceleration patterns were also calculated weekly. Results The starters exposed larger accumulation of acute and chronic workload in the mid-season (p = 0.008, d = −1.24; p = 0.006; d = −1.31) and end-season (p = 0.001, d = −1.66; p = 0.001; d = −1.62), respectively. The metabolic power average, acceleration, and deceleration were remarkably high in starters over all periods of the season (P > 0.05), excepted high-intensity deceleration zone for preseason (> −4 m/s2; p = 0.149). Conclusion Starters accumulated large exposure of acute and chronic workload and high-intensity of locomotor characteristics over a full professional football season. Consideration to balance the deficiency of weekly workloads between line-up players and substitutes/reserve players is essential to establish beneficial approach of team square.