Strength training: how often is enough?

The number of training sessions performed per muscle group – usually counted per week – is called (training) frequency [1]. Depending on your level of fitness, the National Strength and Conditioning Association [2] recommends 2 to 3, 3 to 4, and 4 to 7 training sessions per week for beginner, advanced, and professional athletes, respectively. The American College of Sports Medicine recommends 2 to 3 and 4 to 5 sessions for beginner, advanced, and professional athletes, respectively [3].

Studies on the subject

A recent systematic review and meta-analysis of 22 studies found that training frequency has a significant effect on strength gains: the effect sizes of 0.74, 0.82, 0.93, and 1.08 increased when training once, twice, three times, and four times per week, respectively, or more [4].

However, a subgroup analysis of studies with equal volume load and those with exercising until muscle failure revealed no significant effect of frequency on muscle strength. Interestingly, differences in age and gender did show significant effects of training frequency on strength. While strength did appear to increase with each additional training session in the middle-aged and elderly group, the trend was not significant. However, in the young adult group, strength gradually increased with each additional training session per week, and the effect of training frequency was significant. With regards to gender, the effect of training frequency on strength was not significant in men, while it was significant in women.

Training until muscle failure

In the same year, Barcelos et al. [5] confirmed the observations that training frequency has no effect on strength or muscle cross-sectional area when strength training is performed until muscle failure. In their study, 20 untrained men (23 ± 4 years) had one leg randomly assigned to a frequency of two-, three-, or five-times weekly strength training over a period of eight weeks. Training units consisted of 9 to 12 repetitions until muscle failure at 80% 1-RM on a leg extension machine. The total training volume was significantly different between groups; however, the increase in strength and vastus lateralis cross-sectional area was not significantly different between groups.

Grgic et al [6] examined the existing literature to illustrate the relationship between training frequency and hypertrophy. Using studies that used direct site-specific measures of hypertrophy, they reported that strength training once per week produced similar hypertrophy than training two or three times per week. When comparing studies that used lean body mass to estimate muscle growth, no significant differences were found between training frequencies either. Grgic et al. concluded that training frequency doesn’t appear to have pronounced effects on hypertrophy under volume-equal conditions.

In a weekly volume-adjusted approach, Gederson et al. [7] examined the impact of frequency of strength training on the increase in muscle mass and strength in well-trained men. Twenty-three subjects (26.2 ± 4.2 years) were randomly divided into two groups: low-frequency and high-frequency strength training. The low-frequency group performed a split-body program, exercising each specific muscle group once per week. The high-frequency group exercised all muscle groups five times a week in each training session. Strength was measured using 1-RM values for squats and bench presses. Muscle mass was measured by dual-X-ray absorptiometry. The research group found that muscle strength and muscle mass improved in both groups when comparing the pre- and post-intervention periods. However, no significant difference was found between the groups in strength and muscle mass.

In a recently published meta-regression, Kneffel and colleagues [8] examined the effects of the frequency of strength training on both strength and hypertrophy in adults over the age of 60. Fifteen studies involving 597 subjects of both sexes were reviewed. The authors showed that improvement in upper and lower body strength depended on exercise frequency, but frequency had no effect on hypertrophy in adults over the age of 60.

Conclusion

In summary, training frequency does not appear to affect strength or hypertrophy when training is performed until muscle failure – even if the total training volume varies significantly. In general, it’s recommended to allow at least 48 hours of recovery between training sessions for the same muscle group [1] to allow the full development of protein build-up [9]. To maintain strength and muscle mass, 1/9 of a training volume of 3 sets of 3 × 8 to 12 repetitions per week seems to be sufficient [10]. This corresponds to one set of 8 to 12 repetitions per week and muscle group.

References

1. Schoenfeld BJ. The mechanisms of muscle hypertrophy and their application to resistance training. J Strength Cond Res. 2010;24: 2857–2872. doi:10.1519/JSC.0b013e3181e840f3
2. G. Gregory Haff, PhD F, N. Travis Triplett, PhD F. Essentials of Strength & Conditioning Fourth Edition. Human Kinetics. 2016.
3. Kraemer WJ, Adams K, Cafarelli E, Dudley GA, Dooly C, Feigenbaum MS, et al. Progression models in resistance training for healthy adults. Med Sci Sports Exerc. United States; 2002;34: 364–380. doi:10.1097/00005768-200202000-00027
4. Grgic J, Schoenfeld BJ, Davies TB, Lazinica B, Krieger JW, Pedisic Z. Effect of Resistance Training Frequency on Gains in Muscular Strength: A Systematic Review and Meta-Analysis. Sport Med. Springer International Publishing; 2018;48: 1207–1220. doi:10.1007/s40279-018-0872-x
5. Barcelos C, Damas F, Nóbrega SR, Ugrinowitsch C, Lixandrão ME, Marcelino Eder Dos Santos L, et al. High-frequency resistance training does not promote greater muscular adaptations compared to low frequencies in young untrained men. Eur J Sport Sci. Taylor & Francis; 2018;18: 1077–1082. doi:10.1080/17461391.2018.1476590
6. Grgic J, Schoenfeld BJ, Latella C. Resistance training frequency and skeletal muscle hypertrophy: A review of available evidence. J Sci Med Sport. Sports Medicine Australia; 2018; doi:10.1016/j.jsams.2018.09.223
7. Gomes GK, Franco CM, Nunes PRP, Orsatti FL. High-Frequency Resistance Training Is Not More Effective Than Low-Frequency Resistance Training in Increasing Muscle Mass and Strength in Well-Trained Men. J Strength Cond Res. NLM (Medline); 2019;33: S130–S139. doi:10.1519/JSC.0000000000002559
8. Kneffel Z, Murlasits Z, Reed J, Krieger J. A meta-regression of the effects of resistance training frequency on muscular strength and hypertrophy in adults over 60 years of age. J Sports Sci. Routledge; 2020; 1–8. doi:10.1080/02640414.2020.1822595
9. MacDougall JD, Gibala MJ, Tarnopolsky MA, MacDonald JR, Interisano SA, Yarasheski KE. The time course for elevated muscle protein synthesis following heavy resistance exercise. Can J Appl Physiol. 1995;20: 480–486. doi:10.1139/h95-038
10. Bickel CS, Cross JM, Bamman MM. Exercise dosing to retain resistance training adaptations in young and older adults. Med Sci Sports Exerc. 2011;43: 1177–1187. doi:10.1249/MSS.0B013E318207C15D