Success Leaves Clues; So Does Science

Tom MacCormick

Strength and Conditioning, Personal Training, Sports Science


Success Leaves Clues; So Does Science - Fitness, strength and conditioning, Training, workouts, hypertrophy, training programs, physique, Body Part Split, SRA


Throughout the history of the iron game bodybuilders have used trial and error and the wisdom passed down from one generation of meathead to the next to determine what works. The evolution of this process led most top bodybuilders to train with a split routine, training each muscle once per week.



In recent times, increasing quantities of research has been conducted on the mechanisms of hypertrophy. One of the areas of interest has been training frequency. Training frequency is how many days per week you train. When it comes to building muscle, not only how many days per week you train, but how many days per week a specific muscle group is trained is of great interest. Most of the literature indicates that training a muscle once per week is sub-optimal. Consequently, know-it-all exercise nerds have mocked anyone who trains a muscle once per week using a split routine.


In the science based community many have shunned the traditional body part splits which worked so well for the likes of Dorian Yates, Ronnie Coleman and Jay Cutler. Instead they favour higher frequency programs and have an attitude of disdain, or even pity, for anyone who dares to train like the bodybuilding greats of yesteryear. Is this intellectually superior self-confidence misplaced? Very possibly.


Before we investigate why, it is important to define exactly what a traditional split routine looks like.


A Typical Body Part Split over a 4-Day Cycle

Monday Chest
Tuesday Back
Wednesday Rest
Thursday Legs & Abs
Friday Arms & Shoulders
Saturday Rest
Sunday Rest


A Typical Body Part Split over a 5-Day Cycle

Monday Chest
Tuesday Back
Wednesday Legs & Abs
Thursday Shoulders & Calves
Friday Arms
Saturday Rest
Sunday Rest


The wisdom of years of bodybuilders states that splitting the body up like this means you can smash a body part, leave time for it to fully recover before hitting it again a week later. It has been believed that training a muscle more frequently will lead to overtraining. Scientific research, however, has proven this to be false.


A muscle doesn’t require a full week of rest to fully recover after training. Direct studies on markers of muscle growth consistently show that muscles grow for up to three days post training. After this there is a plateau and subsequent decline in rates of muscle protein synthesis. Thus, training a muscle every three days is a good rule of thumb when trying to maximise hypertrophy. If you follow a sensible nutrition plan and get decent sleep then this will provide ample opportunity for full recovery and growth to take place.


This whole process is described by the SRA (Stimulus, Recovery, Adaptation) curve. Training is the stimulus, after which the body must recover back up to baseline before adaptation can occur. Every training session and the period after it leading up to the next session can be described by the SRA curve. To make optimal progress your program should be organised so that the next training session for a muscle occurs at it the adaptive peak of the SRA curve. This will be every 2-4 days depending upon the muscle group and not every 7 days as promoted by the bro’s.


Given the SRA curve for a muscle is complete in under a week then you are actually de-training ever so slightly when you wait a week to hit the muscle again. It is left dormant, fully recovered, and ready to go for up to 5 days before receiving another stimulus. This means you are leaving progress on the table. Think of it this way…if you train a muscle once per week then it gets 52 “growth” signals a year. Train it twice a week and you get 104 of these signals. Who do you think is going to build bigger muscles?



What Does the Science Say About Training Frequency?

The literature indicates that splitting the same training volume into more frequent training sessions is superior for hypertrophy. This is likely because the hypertrophic stimuli are distributed more optimally over the course of the week in higher frequency training approaches.


Brad Schoenfeld’s study titled, Influence of Resistance Training Frequency on Muscular Adaptations in Well-Trained Men, showed that a total body high frequency training plan was more effective than a once per week split routine for hypertrophy. Furthermore, sports scientist Chris Beardsley, summed the existing research up when saying that a “trend towards a higher volume-matched frequency leading to greater hypertrophy in trained subjects.”


The weight of scientific evidence suggests that training a muscle group two times a week is better than once per week. The research is not clear whether training a muscle more often than twice per week is better for muscle growth. As a result, we can conclude (for now) that training a muscle twice a week is suitable for optimizing hypertrophy.


Based on the evidence that training once per week is sub-optimal for hypertrophy, body part splits have gotten a lot of criticism in recent years. Many of the evidence based community have claimed that typical splits are a waste of time. Most experts would agree that a trainee will see faster and more efficient progress using a program that hits each individual muscle group with a higher frequency.


Training a muscle twice per week appears to be where most experts have settled based on the current weight of evidence. Brad Schoenfeld, in particular, has done great things in terms of allowing us to use science to guide our programming decisions. Schoenfeld himself states that “training a (muscle group) minimum of 2 days a week is needed to maximise muscle growth.”


So, what gives? Thousands of bodybuilders have trained following a body part split and have got great results. They train each muscle once per week. Based on what science tells us this appears to be an epic fail. Real world results, however, tell a different story.


It seems that split routines can’t be all bad. Logically, in fact, we must conclude there is plenty right with them.



So, what is right about a split routine and why doesn’t it match up with what the science is telling us?


To answer this question a closer examination of the typical body part split is instructive.

Obviously, each muscle group gets its own training session each week. Thus, the assumption is that each muscle is only trained once per week. You know what they say about making assumptions, right? It makes an ass out of you (u) and me. Ass-u-me, get it?


So, while you might assume that all the muscles are getting trained once per week you would, in fact, be wrong. This is one of the biggest misnomers about body part splits. How so?


Because many of the secondary assistance muscle groups get worked on an additional day. Take International Chest day (aka Monday) as an example. The triceps and anterior delts take a pummelling during all pressing movements. Likewise, the biceps and rear delts get a tonne of stimulation on back day. If deadlifts are incorporated into back day (they often are) then even the legs get some work.


If we took a straw poll of the most popular exercises for triceps amongst gym rats, dips and close grip bench press would generally rank pretty high. Guess what? Dips and close grip benches hit the pecs hard so, they get a second stimulus each week too. In fact, upon closer inspection, most major muscle groups get hit indirectly a second time when following a traditional spilt. Check out these handy tables below to see what I mean.


4-Day Split

   Chest Back

Legs &


Arms &


Total Per


Chest ✔︎     ✔︎ 2
Back   ✔︎     1


(If deadlifts


✔︎   2
Biceps   ✔︎   ✔︎ 2


✔︎     ✔︎ 2
Anterior Deltoids ✔︎     ✔︎ 2
Lateral Deltoids       ✔︎ 1
Posterior Deltoids   ✔︎   ✔︎ 2
Abs     ✔︎   1
Calves     ✔︎   1


5-Day Split

   Chest Back

Legs &


Shoulders & 



Total Per


Chest ✔︎       ✔︎ 2
Back   ✔︎       1


(If deadlifts


✔︎     2
Biceps   ✔︎     ✔︎ 2


✔︎     ✔︎ ✔︎ 3
Anterior Deltoids ✔︎     ✔︎ ✔︎ 3
Lateral Deltoids       ✔︎   1
Posterior Deltoids   ✔︎   ✔︎   2
Abs     ✔︎     1
Calves     ✔︎ ✔︎   2


On the 4-day split everything other than back, lateral delts, calves and abs get trained twice per week.


The abs actually get a lot of stimulation from chin up variations, bent over rows and military presses. If these exercises are included on back and shoulder day, then the abs get activated to a good degree up to three times a week. That just leaves the back, lateral delts and calves at a training frequency of once per week. The 5-day split is very similar except the calves are hit twice. This means only the back and lateral delts are undertrained. When you consider this, it is little surprise that most guys lack size in these muscles.


So, I’d argue that rather than going against the prevailing science, the bodybuilders have been onto something all along. The phrase success leaves clues springs to mind.


Now we have established that those large, muscular, lean guys do actually know a thing or two about getting bigger and leaner (shock horror!), it is time to try and fine tune the body part split to make it optimal.


Improving on the Traditional Body Part Split

There are any number of ways to change the bro split to try and optimise training frequency. One glaring omission from the above split is the training frequency for back and lateral delts (I would also argue that legs are being neglected even if deadlifts are done on back day). Great alternatives include switching to a push, pull, legs or an upper/lower plan. If, however, you enjoy a body part split and want to maintain that training structure then you could make the following adjustments to your plan to allow for a more even training frequency:


Day 1 Chest & Shoulders
Day 2 Back (Heavy) & Lateral Delts
Day 3 Legs & Abs
Day 4 Arms & Shoulders (Heavy), Back (Light)


Doing this will get you hitting everything except legs with a good amount of volume twice per week. I think this is an improvement on the basic split routines most gym junkies follow. It is also a great way to grow the beach muscles, but the legs are neglected. Want to pack on some size to your legs? Then I would suggest switching your split after 4-6 weeks of the above to train legs twice per week like this:


Day 1 Legs & Arms
Day 2 Back & Lateral Delts
Day 3 Legs & Abs
Day 4 Chest & Back (Tag on lateral delt work)


Then in the next block of training, you could switch focus again. Perhaps to shoulders.


Assuming you aren’t married to body part splits you can use the above info to build a plan which has you training every muscle twice per week. This can be set up to suit your schedule and training preferences.


Want to Maximise Efficiency?

Then you can add some isolation work for smaller muscles to days when you train bigger muscles with compound movements. Chest day, for example, can very easily become a ‘push’ day, which targets your shoulder and triceps too. Add in some lateral raise, reverse flyes and rope press downs and you effectively kill 3 birds with one stone.


Alternatively, if you have a lagging muscle group you can ‘tag’ some extra work on for these to another session or two. Biceps a weak point? Put them in with chest day and shoulder day and they will get 3 training days per week when you include the stimulation from back day.


So, there you have it. Success leaves clues and so does science. Do not ignore either. Instead, do as Bruce Lee suggests and adapt what is useful, reject what is useless, and add what is specifically your own. If you combine the best information from both old school bodybuilders and cutting edge research scientists then you can fine tune your training and transform your physique.

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