The Minimum Effective Training Dose Required to Increase 1RM Strength in Resistance-Trained Men: A Systematic Review and Meta-Analysis.

Background: Increases in muscular strength may increase sports performance, reduce injury risk, are associated with a plethora of health markers, as well as exerting positive psychological effects. Due to their efficiency and effectiveness in increasing total body muscular strength, multi-joint exercises like the powerlifts, i.e.: the squat (SQ), bench-press (BP) and deadlift (DL), are widely used by active individuals as well as athletes in the pursuit of increasing strength. To date, the concept of a minimum dose, i.e. "what is the minimum one needs to do to increase 1-repetition maximum (1RM) strength?" has not been directly examined in the literature, especially in the context of the powerlifts. This review aims to explore the current available evidence around the minimum effective training dose required to increase 1RM strength in trained individuals in an attempt to enhance the practical guidelines around resistance-training as well as provide active individuals, athletes and coaches with more flexibility when designing a training protocol.

Methods: One reviewer independently conducted the search in a PRISMA systematic approach using PubMed, SportDiscus and Google Scholar databases. The databases were searched with the following search terms/phrases and Boolean operators: "training volume" AND "powerlifting" OR "1RM strength" OR "powerlifters", "low volume" AND "powerlifting" OR "powerlifting" OR "1RM strength", "high vs low volume" AND "powerlifting" OR "1RM strength", "minimum effective training dose 1RM". Meta-analyses were performed to estimate the change in 1RM strength for the lowest dose group in the included studies.

Results: From the initial 2629 studies, 6 studies met our inclusion criteria. All identified studies showed that a single set performed minimum 1 time and maximum 3 times per week was sufficient to induce significant 1RM strength gains. Meta-analysis of 5 studies showed an estimated increase for overall 1RM of 12.09 kg [95% CIs 8.16 kg-16.03 kg], an increase of 17.48 kg [95% CIs 8.51 kg-26.46 kg] for the SQ, and 8.25 kg [95% CIs 0.68 kg-15.83 kg] for the BP. All of the included studies contained details on most of the variables comprising "training dose", such as: weekly and per session sets and repetitions as well as intensity of effort. Specific information regarding load (%1RM) was not provided by all studies.

Conclusions: The results of the present systematic review suggest that performing a single set of 6-12 repetitions with loads ranging from approximately 70-85% 1RM 2-3 times per week with high intensity of effort (reaching volitional or momentary failure) for 8-12 weeks can produce suboptimal, yet significant increases in SQ and BP 1RM strength in resistance-trained men. However, because of the lack of research, it is less clear as to whether these improvements may also be achievable in DL 1RM strength or in trained women and highly trained strength athletes.

Registration: This systematic review was registered with PROSPERO (CRD42018108911).