How often should I work out? This common question is much harder to answer than it seems on the surface. People looking to lose weight, gain weight, maintain but build strength, etc. all ask the same question but need a different answer for it to be correct. For this instance, the question will be taking in such a way to address the desire to drive maximum hypertrophy. Below is a modified version of an email I had sent to a colleague as we discussed their 2d/wk workout recommendation.
The Email
To answer this question, I started with looking into muscle protein synthesis (MPS) and how long that lasts. I found that 24-48 hrs after resistance training (RT), the growth impacts remain. This seemingly proved my thought on only needing a single day off from a given muscle group. As I dug further, I came across this, identifying that muscular hypertrophy is not impacted by frequency (outside of 2 sessions/wk is better than one), so long as overall weekly volume is the same. This was interesting but also caused me to pause and reframe the situation.
I came up with a list of variables, not just MPS, that I believe would need to be recovered before instigating a second, third, or fourth training session in a given week.
The Variables
Muscle Protein Synthesis (MPS) – If the stimulus to grow muscle is gone, you are no longer optimally training.
Muscle Protein Breakdown (MPB) – If you are still depleting muscle/protein from your last session, you should not compound the breakdown with another.
Neuromuscular Performance (NMP) – Lack of NMP recovery may lead to lower force output and therefore lower mechanical tension (MT) and less optimal hypertrophy.
Inflammation – High inflammation may cause pain, swelling, and hinder performance leading to injury or poor hypertrophy.
Glycogen Repletion – Low glycogen can reduce performance (via reduced MT) and hypertrophy (via lowered mTOR signaling)
Tendon/Ligament Remodeling – Like inflammation, continuous tendon/ligament depletion/strain may lead to injury and poor performance and hypertrophy
Central Nervous System (CNS) – High levels of fatigue and exhaustion can lead to poor RT sessions and potentially injury.
All of these should be considered when answering “how often should I work out?”
The Process
I then researched each of these variables to see if they would be hindered in a 48hr recovery window.
MPS – As shown above and widely recognized, MPS extends for 24-48 hrs after RT. If all other factors allow, training again within that window is ideal.
MPB – MPB tends to normalize after 24 hrs so 48 hrs between sessions would be an adequate rest period to avoid MPB stacking.
NMP – NMP force returns to normal after 48 hrs despite a sense of fatigue potentially persisting for 72 hrs. That fatigue did not impact performance and therefore, 48 hrs between RT would be adequate in terms of NMP.
Inflammation – My understanding was off. Inflammation is necessary for adaptation. While full recovery may take 96+ hrs, full recovery is not desired/required. This is a non-factor outside of extremes that may cause pain/injury.
Glycogen Repletion – Given an appropriate diet (not in a deficit or eating low-carb), glycogen is generally fully repleted in 24-48 hrs. This supports that a 48 hr period between RT sessions is adequate.
Tendon/Ligament Remodeling – Much like inflammation, this was misunderstood. Fully recovery would weaken tendons and consistent use builds tendon/ligament strength concurrently during use. Multiple weeks would be required for full recovery and they would become dormant and weaker.
CNS – Generally, 48 hours are needed to fully recover CNS but 72 hours could be needed after extreme sessions.
So… How often should I work out?
You only need 72+ hours after extreme workouts or if an you are in a calorie deficit/eating limited carbohydrates.
It is important to note that psychological factors are at play. Some people cannot maintain an more intense regimen than 2 days/week of intense workout. 2 days is certainly better than 0. If burnout is a concern, stay conservative.
Next time someone asks “how often should I work out” – understand the nuance to the question and provide a tailored answer as to best address their needs.
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