A major new study was just published:
As the title suggests, the researchers compared a weekly training frequency of 2x vs. 4x. The abstract reads: “only the low frequency group enhanced arm circumference and elbow flexors thickness values and decreased their fat mass… only the low frequency protocol increased upper body hypertrophy and improved body composition.”
Here’s the full abstract:
The present study compared the effects of two weekly-equalized volume and relative load interventions on body composition, strength and power. Based on individual baseline maximal strength values, eighteen recreationally trained men were pair-matched and consequently randomly assigned to one of the following experimental groups: a low volume per session with a high frequency (LV-HF, n = 9) group who trained 4-days (Mondays, Tuesdays, Thursdays and Fridays) or a high volume per session and low frequency (HV-LF, n = 9) group who trained 2-days (Mondays and Thursdays). Both groups performed two different routines over 6 weeks. Participants were tested pre- and post- intervention for maximal strength, upper body power, fat-free mass, limb circumferences and muscle thickness. Compared to baseline values, both groups increased their fat-free mass (HV-LF +1.19 ± 1.94; LV-HF +1.36 ± 1.06 kg, p<0.05) and vastus medialis thickness (HV-LF +2.18±1.88, p<0.01; LV-HF +1.82±2.43 mm, p<0.05), but only the HV-LF group enhanced arm circumference (1.08±1.47cm, p<0.05), elbow flexors thickness (2.21±2.81 mm, P<0.01) values and decreased their fat mass (-2.41 ± 1.10, P<0.01). Both groups improved (p<0.01) the maximal loads lifted in the bench press (LV-HF +0.14 ± 0.01; HV-LF +0.14 ± 0.01 kg.body mass-1) and the squat (LV-HF +0.14 ± 0.06; HV-LF 0.17 ± 0.01 kg.body mass-1) exercises as well as in upper body power (LV-HF +0.22 ± 0.25; HV-LF +0.27 ± 0.22 watts.body mass-1) Although both training strategies improved performance and lower body muscle mass, only the HV-LF protocol increased upper body hypertrophy and improved body composition.
This study is making the rounds in the fitness community as proof that training a muscle 4x per week is inferior to training it 2x.
Before jumping to conclusions, however, let’s go into detail.
The study had 9 men perform the following 2 workouts each week for 6 weeks total. The low frequency group trained twice a week (2x), performing each workout once with 4 sets per exercise. The high frequency group trained 4 times per week (4x), performing each workout twice a week with 2 sets per exercise. So both groups performed the same total amount of sets per week and trained the same exercises. The training intensity was 75% of 1RM (8-12 RM) in both groups.
If you look at the splits, you can see that this study is not a regular comparison of training each muscle 4x or 2x per week. The 2x frequency group was only training their legs, chest and lateral delts once a week compared to 2x in the 4x frequency group. However, the training frequency for the back and arms was 2x vs. 4x, as these muscles were trained every workout in both groups. So for the majority of the body, this was a comparison between training a muscle once a week vs. twice a week, but for the back and arms specifically it was 2x vs. 4x. I have no idea why the authors used this weird design instead of a comparison between, say, an upper-lower and a full-body split, but it is what it is.
Another important clarification is regarding the subjects. Although they were ‘strength trained men’, they were complete novices. Before the study, they were barely benching their bodyweight for 1 rep and they were squatting only a little bit more than 4 plates on the bar. The low frequency group was also overweight with 22% body fat.
Now that we’ve clarified the study design, let’s look at the results. The following table summarizes the study findings.
Astute readers will notice there were no significant differences between groups for any outcome. The abstract makes it sound like there were based on the significance level of pre-post changes, but that’s just the result of poor statistical power with only 9 subjects per group and a 6 week study duration. What matters is the difference between groups. And there was none. There were 2 trends though.
- There was a trend for increased bodyweight in the 2x frequency group, but the relevance of this is questionable, since total fat-free mass gains as well as all other 5 measures of muscle growth did not differ between groups. Plus, their diets were not controlled.
- There was a trend for greater gains in bench press strength in the 2x frequency group. However, it’s a 12 kg gain compared to a 11 kg gain… In novices. And the trend disappeared entirely when controlled for bodyweight. There was also no difference in squat gains, which were trained with the same frequency, or either measure of bench press power.
Still, all in all the 2x frequency group did seem to get slightly better results, particularly for the arms. All below the threshold of statistical significance, but in exercise science we often have to go beyond that due to the poor quality of research available compared to other fields. So this study may be interpreted as evidence that novices should err on the side of training each muscle 1-2x per week compared to 2-4x.
Better results with a lower training frequency would have been a novel finding. Literally every study on training frequency so far had found neutral or beneficial effects of higher training frequencies. There is a strong trend that the benefits of higher training frequencies only manifest in well trained individuals with the most relevant study available still being the Norwegian Frequency Project, showing greater strength and size gains in the Norwegian powerlifting team when training each muscle 6x vs. 3x per week. The authors also mention this in their review of the literature: “It is conceivable that early-phase adaptations in less-well trained individuals are less sensitive to alterations in frequency and that benefits reach more notable differences with a progressively higher training level.”
Lastly, it should be emphasized that this study, like most studies, equated training volume across groups. This is never the case in practice. Higher training frequencies typically result in higher repetition training volumes due to spending less time in a fatigued state. This is arguably in fact the main benefit of higher frequency training, providing an effective and time efficient manner for advanced trainees to increase their training volume.
In novices training each muscle 1-2 vs. 2-4x per week with the same training volume, there were no significant differences in the development of strength, power or body composition. There was a tentative trend for inferior results in the 2-4x frequency group though, suggesting that novice trainees have no business training each muscle more than twice a week.
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