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Clarke, R, Read, PJ, De Ste Croix, MBA, and Hughes, JD. The deceleration deficit: a novel field-based method to quantify deceleration during change of direction performance. J Strength Cond Res 36(9): 2434–2439, 2022—The study investigated the relationship between linear and change of direction (COD) speed performance components and the individual differences between deceleration deficit (DD) and COD deficit (CODD). Thirty-six subjects (mean ± SD : age = 20.3 ± 2.9 years; stature = 175.2 ± 7.7 cm; and body mass = 78.0 ± 16.7 kg) completed 3 trials of a 505 test in both turning directions (dominant [D]; nondominant [ND]) and 3 15-m linear sprints. Deceleration deficit was calculated by the 15-m approach in the 505 test, minus the athlete's linear 15-m sprint time. To compare individuals CODD and DD, z-scores were calculated, and moderate worthwhile changes (MWCs) were identified between these deficit z-scores. Significant correlations were identified between linear sprints and 505 time (D: r = 0.71, 0.74; P < 0.01. ND: r = 0.76, 0.75; P < 0.01) for 10-m and 15-m sprint. respectively, and between 505 performance and CODD (D: r = 0.74; P < 0.01. ND: r = 0.77; P < 0.01) and DD (D: r = 0.41, P < 0.05. ND: r = 0.44, P < 0.01). Deceleration deficit was significantly related to CODD (D: r = 0.59; P < 0.01. ND: r = 0.62; P < 0.01); however, 78% of subjects demonstrated differences between these deficit measures greater than an MWC. In conclusion, linear speed has the strongest significant relationship with 505 performance. Deceleration deficit could provide a more isolated construct than CODD which may be related to an athlete's deceleration capabilities. [ABSTRACT FROM AUTHOR]

Resource constraints complicate load monitoring practices in some academies, which is problematic based on load-injury associations surrounding periods of rapid non-linear growth. Limited research has explored relationships between maturation and perceived psycho-physiological response to activity and associated neuromuscular performance changes. This study aimed to quantify neuromuscular and psycho-physiological responses to standardised activity and analyse whether dose-responses were moderated by maturation. Fifty-seven male soccer players (age: 14.1 ± 0.9 years; stature: 165 ± 10 cm; body mass, 57 ± 9 kg; percentage of predicted adult height 92.7 ± 5%) from two Elite Player Performance Plan (EPPP) academies completed the youth soccer-specific aerobic fitness test (Y-SAFT60). Countermovement jump (CMJ), reactive strength index (RSI), absolute (ABS) and relative leg stiffness (REL) were measured pre–post the Y-SAFT60 with playerload (PL), heart rate (HR), total distance (TDist) and differential ratings of perceived exertion (dRPE) used as markers of load and intensity. A moderation model was employed to analyse interactions of maturation as a continuous variable. Analysis indicated no significant interaction (p <0.05) between maturation and neuromuscular performance but RPE-Technical demonstrated significant interactions (p = 0.01). Slope analysis indicated four variables (PL, RSI, ABS and REL) that demonstrated significance at various stages of maturation, most notably aligning with peak height velocity (∼87–96% PAH). Tentatively, we propose that maturational developments in the neuromuscular system offer some mechanistic explanation to the varied dose-responses observed. It is therefore important that maturation is habitually considered within prescription of training programmes and that further empirical studies are completed to determine maturity specific dose-responses. [ABSTRACT FROM AUTHOR]