I can attest to these findings. For optimal life, simply strengthening even just once a week is beneficial and may, in fact, prove MOST beneficial for the average populace.
Certain cell turnover rates don’t change. That is, you cannot replace tendon, or increase ligament and bone density faster than about 6 months. So, if we compare the result of someone training 6 days per week, twice per day, for 12 weeks, to someone training once per week for 12 weeks, we won’t find statistically significant differences in connective and skeletal tissue at that time. Moreover, if we fast forward 3 years and find the high frequency person quit at week 12, while the once weekly participant is still going once per week, what we will find is the once weekly person outrageously more powerful, mobile, healthier and dramatically changed versus the twice per day fanatic.
On paper, we may think, “high frequency person got 144 training sessions in versus low frequency got 156: not that different.” Actually, it’s COMPLETELY different. Imagine this were monetary investing. One person saved A LOT of money for 12 weeks, overextended himself, and then spent all the savings (and more). He’s in debt. The other person saved a manageable amount every week for three years, never spent a cent, and is increasingly putting more into investment every week.
People falsely think they have to be like the first person. But even the first person wishes he would’ve been like the second.
Paper here:
https://www.jyu.fi/en/current/archive/2019/02/resistance-training-even-as-little-as-once-per-week-benefits-older-individuals