Perhaps the most common reason people do not exercise is lack of time. The beauty of resistance training especially when you follow the advice here is exercise doesn’t require much of a time commitment. In the first study, I published participants exercised 3 times per week for about 35-45 minutes per session. Total training time per week was about 2-2.5 hours that resulted in improvements in muscle mass and strength following the 8-week intervention (Thomas & Burns, 2016).
Keep in mind this study was conducted with trained participants. I have since adapted my recommendations to less strength training per week.
Regarding resistance training prescription there appears to be a minimum dosage needed and this minimum dosage is less than most follow.
Strength training two days per week at 30 minutes per session does produce tremendous improvements in muscle mass and strength.
Further, I have witnessed many individuals improve in strength and muscle mass completing just one total-body strength session weekly with the total training time of that session being less than 30 minutes.
In my training, I exercise twice per week with each session lasting 15-20 minutes. I have been strength training for over 30 years and I have found that less is more.
When you exercise using the basic movements that engage a lot of muscle mass you don’t need much training volume.
We have seen this at my training center over and over. In fact, I haven’t had one client who trained at this frequency not improve in strength and muscle mass in short order.
Thomas, M. H., & Burns, S. P. (2016). Increasing Lean Mass and Strength: A comparison of high-frequency strength training to lower frequency strength training. International Journal of Exercise Science, 9(2), 159-167.