Functional Speed Reserve as a Proxy for the Anaerobic Speed Reserve Using the Critical Speed Concept

Background. Although maximal sprint speed (MSS) and the anaerobic speed reserve (ASR) provides valuable information about an athletes' speed profile, these parameters fall short of providing important information about submaximal metabolic thresholds. The only field test that can offer an estimate of a sub-maximal metabolic threshold is the 3-minute all-out test for running (3MT), which delivers three parameters of interest: the critical speed (CS), fatigability constant (D'), and 3MT-specific maximal running speed (MS3MT). Objectives. We offer an alternative to the ASR, termed the 'functional' speed reserve (FSR). Therefore, this study's purpose was two-fold: firstly, to compare MSS to MS3MT and FSR to ASR, and secondly, to determine the correlations between ASR, FSR, and D'. Methods. Thirty-two participants volunteered for the study (age: 22.50 ± 4.32 years; height: 1.67 ± 0.78 m; body mass: 66.58 ± 11.30 kg) and completed a graded exercise test (GXT), 3MT, and 40-m sprint test following familiarization bouts for each test. Results. MSS and MS3MT were strongly correlated (r = 0.93, p < 0.001). The ASR and FSR were also strongly correlated (r = 0.77, p < 0.05), with the FSR also showing a strong correlation with D’ (r = 0.77, P < 0.05). Conclusion. The 3MT provides a viable, arguably more ecological alternative to the ASR (i.e., FSR) and provides additional parameters such as CS, D', and MS3MT. Field testing based on the 3MT can offer coaches and athletes unique performance insights and tools to program and effectively prescribe training interventions.