Determinants of last lap speed in paced and maximal 1500-m time trials

Purpose The present study identified the physiological and performance characteristics that are deterministic during a maximal 1500-m time trial and in paced 1500-m time trials, with an all-out last lap. Methods Thirty-two trained middle-distance runners ( n = 21 male, VO 2peak : 72.1 ± 3.2; n = 11, female, VO 2peak : 61.2 ± 3.7 mL kg −1 min −1 ) completed a 1500-m time trial in the fastest time possible (1500 FAST ) as well as a 1500 MOD and 1500 SLOW trial whereby mean speed was reduced during the 0–1100 m by 5% and 10%, respectively. Anaerobic speed reserve (ASR), running economy (RE), the velocity corresponding with VO 2peak ( V VO 2peak ), maximal sprint speed (MSS) and maximal accumulated oxygen deficit (MAOD) were determined during additional testing. Carnosine content was quantified by proton magnetic resonance spectroscopy in the gastrocnemius and expressed as a Z -score to estimate muscle fibre typology. Results 1500 FAST time was best explained by RE and V VO 2peak in female runners (adjusted r 2 = 0.80, P