Abstract
Background Endurance cycling performance is determined by maximal oxygen uptake (VO 2 max), maximal metabolic steady state (MMSS), non-oxidative energy contribution (i.e., anaerobic capacity and anaerobic power) and cycling efficiency and power related to VO 2 max (pVO 2 max). Strength training can improve these variables. However, is yet to be clarified the effects of heavy strength training (≥ 80% of one repetition maximum). Aim The aim of this systematic review with meta-analysis was to analyse heavy strength training effects on physiological determinants of endurance cyclists’ performance. Methods A systematic search was carried out in PubMed, Web of Science and Scopus including articles indexed up to February 2025. Following the PICOS criteria: Population, endurance cyclists aged ≥ 18 years or older, without restriction of sex or performance level; Intervention, heavy strength training (≥ 3 weeks); Comparator, group that performed cycling endurance training without receiving heavy strength training; Outcome, physiological determinants of endurance cycling (i.e., VO 2 max, pVO 2 max, MMSS, cycling efficiency, anaerobic capacity, and anaerobic power) and/or cycling performance (i.e., time to exhaustion and time trial [combined for analyses]), measured before and after the intervention and; Study design, randomised and non-randomised controlled studies. Risk of bias in studies was assessed (PEDro), and certainty of evidence at the outcome level (GRADE). Random-effects meta-analyses (for VO 2 max, pVO 2 max, MMSS, anaerobic capacity, anaerobic power and cycling performance), three-level random-effects meta-analyses (for cycling efficiency) and moderator analyses (i.e., participant and intervention characteristics) were conducted. Significance was set as p ≤ 0.05. Results Included studies (n = 17) comprised 262 participants (60 female) with a mean initial VO 2 max level of 61.25 ml/kg/min, with interventions lasting between 5 and 25 weeks, with 1–3 sessions per week. Compared to controls, heavy strength training showed a significant effect on cycling efficiency (effect size [ES] = 0.353, p = 0.012, LRT level2; level3 = 1), anaerobic power (ES = 0.560, p = 0.024, I 2 = 29.100) and cycling performance (ES = 0.463, p = 0.016, I 2 < 0.001), with no significant effect on VO 2 max, pVO 2 max, MMSS, and anaerobic capacity (all p ≥ 0.263, I 2 < 0.001). No significant moderating effect was found for participant characteristics (i.e., sex, body mass, height, performance level, and strength training experience) or intervention characteristics (i.e., duration, training frequency, total sessions) (all p ≥ 0.170). Results presented low certainty of evidence. Conclusion Heavy strength training can improve cycling performance (i.e., time to exhaustion; time trial) in endurance cyclist. This improvement may be mainly due to an improvement in cycling efficiency and anaerobic power. These results occur without changes in VO 2 max, pVO 2 max, MMSS or anaerobic capacity. Nonetheless, the low certainty of evidence precludes robust recommendations regarding optimal implementation of heavy strength training. Protocol registration The original protocol was registered ( https://osf.io/75xt4 ) at the Open Science Framework. Graphical abstract