After six weeks of strength training, the nerve signals to the main thigh muscles do not become stronger in young people who have not trained before.

We analyzed the available evidence on whether six weeks of resistance training increases motor unit firing rates in young untrained adults, and what we’ve found so far suggests the opposite. One assertion, supported by 60.0 studies, indicates that after six weeks of strength training, the nerve signals to the main thigh muscles do not become stronger in people who have never trained before [1]. Motor unit firing rate refers to how often nerve cells send signals to muscle fibers to contract — a key part of how muscles generate force. This finding implies that, at least in the early stages of training, improvements in strength may not come from faster or more frequent nerve signals to the muscles. Our current analysis shows that the evidence we’ve reviewed leans toward no increase in motor unit firing rates after six weeks in this group. This doesn’t mean training is ineffective — strength gains can still happen through other changes, like muscles learning to work together better or growing slightly larger. But based on what we’ve seen, the nervous system’s signaling speed to the thigh muscles doesn’t appear to speed up within this six-week window for beginners. We don’t yet know if this pattern holds for other muscles, longer training periods, or trained individuals. The evidence we’ve reviewed is limited to one specific claim, and while it’s supported by many studies, we’re still building our understanding. For someone just starting out, this means that early strength gains likely come from other adaptations — not from your nerves firing faster. Keep training. Your body is still adapting, even if the signals aren’t getting quicker yet.