The dRM-Index: Applicability of the Differential Respiratory-to-Muscular Training Load Index in Young Female Soccer Players

This study described the differential respiratory and muscular perceived training loads (RPEres-TL and RPEmus-TL) within and between sessions, and investigated the associations between neuromuscular performance and the dRM-Index (i.e., the ratio of differential respiratory and muscular perceived training loads: RPEres-TL divided by RPEmus-TL) among youth female soccer players. Thirteen outfield players (age: 17 ± 1 years) of the third team of a Women's Soccer Spanish First Division Club completed the 14-week study period. Neuromuscular performance tests (countermovement jump [CMJ], CMJ arm swing, single leg CMJ, and 30-m sprint tests) were conducted before (T1) and after (T2) the study period. Players improved neuromuscular performance (p < 0.05; Cohen's d < 1.29; small-to-large) from T1 to T2. RPEres-TL was greater than RPEmus-TL for training sessions performed four (M-4: p < 0.001; Cohen's d = -0.61; moderate) and one (M-1: p = 0.01; Cohen's d = -0.37; small) days before the match. Baseline sprint performance showed large correlations with the dRM-Index during M-2 (p < 0.05; r < 0.59), M-1 (p < 0.05; r < 0.60) and matches (p < 0.05, r < 0.66). Differential RPE allows the analysis of the TL distribution during the week providing additional insights into the training workload. Baseline sprint performance can be used to forecast the differed heterogeneous individual cardiovascular and neuromuscular responses to the sessions. This initial study on the dRM-Index offers a novel and practical approach to individualize and optimize the training process of youth female soccer players.