A new approach to quantify internal and external training load for intermittent sports

Abstract

The aim of this study was to propose a modified training impulse method (TRIMP) to quantify internal training load (ITL) in intermittent team sports and examine its relationship with external training load (ETL) during a preparatory period. Over 12 weeks, 11 male youth field hockey players (14.41 ± 0.51 years) were evaluated in regard to their ETL using triaxial accelerometers (Actigraph) and data was later contrasted with ITL, which was measured using heart rate (HR) monitors (Polar Team2) by four different TRIMP methods: Banister´s (bTRIMP), Edwards´s (eTRIMP), individualized (iTRIMP) and modified (mTRIMP). A correlation was found between HR (beat/min) and ETL (r = 0.699, R2 = 0.489, p < 0.01) and among TRIMP methods (r = 0.808-0.984, p < 0.01), however, the consistency between methods did not agree (p < 0.01). The ETL correlated in all TRIMP methods: bTRIMP (r = 0.509, R2 = 0.259, p < 0.01), eTRIMP (r = 0.336, R2 = 0.113, p < 0.01), iTRIMP (r = 0.224, R2 = 0.050, p < 0.01) and mTRIMP (r = 0.516, R2 = 0.267, p < 0.01). The proposed mTRIMP can be a valid option for ITL quantification; furthermore, indexes combining ITL and ETL should be used for a complete training assessment.