Eur J Appl Physiol. 2025 Jul 9. doi: 10.1007/s00421-025-05883-2. Online ahead of print.ABSTRACTBACKGROUND: Endurance cycling performance is determined by maximal oxygen uptake (VO2max), maximal metabolic steady state (MMSS), non-oxidative energy contribution (i.e., anaerobic capacity and anaerobic power) and cycling efficiency and power related to VO2max (pVO2max). 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., VO2max, pVO2max, 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 VO2max, pVO2max, 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 VO2max 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, LRTlevel2; level3 = 1), anaerobic power (ES = 0.560, p = 0.024, I2 = 29.100) and cycling performance (ES = 0.463, p = 0.016, I2 < 0.001), with no significant effect on VO2max, pVO2max, MMSS, and anaerobic capacity (all p ≥ 0.263, I2 < 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 VO2max, pVO2max, 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.PMID:40632222 | DOI:10.1007/s00421-025-05883-2