Double Your Muscle, Maximize Your Endurance Gains: Train in the PM, not the AM, and Do Your Cardio Before Weights

Both, time and exercise order matter - at least when untrained subjects have trained for at least 12 weeks.
The debate about whether you should (a) do cardio and weights together and (b) whether you shall do either or both in the AM or PM for maximal muscle anabolism is older than the SuppVersity and has thus been addressed in many of the hitherto published approx. 2300 articles on suppversity.com.

The reason you should still read today's article, however, is that the approach to the topic is a bit different than usual, so that the study, which certainly leaves much to be desired (more on that in the bottom line), adds more practically relevant (which you cannot say about studies measuring the testosterone : cortisol ratio, for example) data.
AM or PM, you got to make sure you slept / sleep enough & well before or after workouts

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Said data has been gathered over 24 weeks during which previously untrained, but healthy participants none of which belonged to either an extreme morning or evening chronotype or worked night shifts followed identical strength (S) and endurance (E) training regimen. The interesting and uncommon thing was was, that these workouts took place either in the AM (m, as in morning) or in the PM (e, as in evening) and were, on top of that, differently ordered (i.e. endurance (E) before strength (S) = E+S or strength (S) before endurance (E) = S+E) - according to cocker we should thus have 2x2 = four groups... and indeed, here they are:
  • mE+S n=9, training in the morning, endurance before strength
  • mS+E n=9, training in the morning, strength before endurance
  • eE+S n=12, training in the evening, endurance before strength
  • eS+E n=12, training in the evening, strength before endurance
In that, the workouts were identical with two workouts per week in the first and two-to-three workouts per week in the second 12-week-period (an additional session was added every two weeks so that all participants performed 5 training sessions in a 2-week period, the reasoning behind this was to "allow further progression in training adaptations" | Küüsmaa. 2016). Here are some details:
"The morning training groups (mE+S and mS+E) performed all training sessions between 6:30-10:00h, while the evening training groups (eE+S and eS+E) performed their training sessions between 16:30-20:00h. The training programs were identical for the E+S and S+E group independent of the training time, only the sequence of strength and endurance training was reversed. Endurance and strength training were combined into the one training session so that no more than a 5-10 minute break was allowed during the two training sections. The duration of the combined endurance and strength training sessions progressively increased from 60 to 120 minutes. All the training sessions were supervised.

Strength training consisted of exercises aimed at improving both maximal strength and muscle hypertrophy and was planned as a whole body periodized program with the main focus on knee extensors and flexors as well as hip extensors. Each training session consisted of three lowerbody exercises: bilateral dynamic leg press, seated dynamic knee extension and flexion. Four to five exercises were performed for other main muscle groups (lateral pull down, standing bilateral triceps push down, bilateral biceps curl, seated military press, or bilateral dumbbell fly, trunk flexors and extensors). Strength training was designed to improve muscular endurance in the first 4 weeks, which was performed as circuit training (intensity 40-70% of 1 RM). The subsequent 4 weeks (weeks 5-8) were designed to produce muscle hypertrophy (intensity 70-85% of 1 RM) and followed by 4 weeks (weeks 9-12) of mixed hypertrophic and maximal strength training (intensity 75-95% of 1 RM). A similar strength training program with slightly higher intensities was carried out also during the second 12 weeks of training" (Küüsmaa. 2016).
The cardio workouts were a mix of interval and continuous cycling on an ergometer. The sessions averaged from 30-50 minutes. Interval (85-100% of HRmax for 4x4 min, 4 min active rest in between) and continuous (65-80% of HRmax) training protocols were performed weekly.
Yes, this study really had it all, HIIT, steady state, weights... and no, that does make it more reliable. Rather than that, it makes it more difficult to identify cause and effect and thus to interpret the results. This is why I would like to warn you: do not to assume that either of the initially raised questions for the optimal workout time and order would be answered by this single study once and for all. Needless to say that this doesn't mean the study results are worthless, but if you feel what worked for the subjects in the study at hand doesn't work for you, don't be a lemming and stick to a protocol of which you feel and see after giving it a fair chance (3-4 weeks) that it's bad for you.
As you'd expect it from a study like this, participants were tested for dynamic leg press 1 repetition maximum (1RM) and time to exhaustion (Texh) during an incremental cycle ergometer test both in the morning and evening before, during (12-week, see Figure 1) and after the 24-week intervention. all relevant information to address the practical value of training in the AM vs. PM and doing endurance before or after weights - a fact I would like to highlight (and applaud to), because that is unfortunately not the case in many other studies that lack practically relevant study outcomes, such as performance increases (here 1RM and Texh) and gains (here CSA values).
Figure 1: Study design and measurements. 1 RM = one repetition maximum in the dynamic leg press; Texh = time to exhaustion during the incremental cycling test; CSA = cross-sectional area; m = morning; e = evening (Küüsmaa. 2016)
I mean, who cares about acute (post workout) levels of exhaustion, 2-6h max protein synthesis or the testosterone to cortisol ratio and its diurnal rhythm if neither of these values can answer the question we are actually asking: Does it help you make extra strength, endurance or muscle gains? Not me (if you care, here's another of these studies, just out, speculating based on questionable markers of a "differential hormonal milieu" and free to read | Burley. 2016), because all these values are as reliable predictors of muscle gains as yesterday's weather forecast for Christmas... well, ok, maybe a bit better, but eventually it's results like those, Küüsmaa et al. present in their recent paper in Applied Physiology Nutrition and Metabolism, that matter:
  • It's the Same (!) Time of the Day That Matters If You Want to Excel | Learn more about the effects of habitual training times on performance!
    1RM gains were similar in the morning (14-19%; p<0.001) and evening (18-24%; p<0.001); no sign time-of-day-effect
  • CSA increased in all groups by week 24 (12-20%, p<0.01), however, during the training weeks 13-24 the evening groups gained more muscle mass; time-of-day main effect; p<0.05)
  • Texh increased in all groups in the morning (16-28%; p<0.01) and evening (18-27%; p<0.001), just as the 1RM gains without effect of the exercise order, but with the data suggesting an advantage of doing cardio first (E+S) at 12 and 24 weeks
The overrated testosterone to cortisol ratio, the scientists assessed as well and even its diurnal rhythms, on the other hand, remained statistically unaltered by the training order or time at any point in the study. So that the study only confirms what I have said before to use the Bro's "holy yardstick of anabolism", i.e. the testosterone to cortisol ratio (T/C) after or in the vicinity of your workouts as an "anabolic guide" won't work, because it's simply not an acceptable predictor of any of the previously mentioned relevant training outcomes (strength, muscle size, and endurance).
Figure 2: Change (%) of the CSA of vastus lateralis (left), endurance performance in the AM (right, top) and PM (right, bottom) in the different training groups - left figure: *sign. (p < 0.05) within-group increase; # sign. different from controls; & sign. time-of-day main (TOD) effect | right figures: ¤ sign. between group differences as indicated; # sign. different from controls; $ sign. order main effect; sign. time-of-day (TOD) main effect (Küüsmaa. 2016).
The actual relevant messages of the study at hand have thus nothing to do with the T or C values or the T/C ratio. Rather than that, the present study "indicate[s] that combined strength and endurance training in the evening may lead to larger gains in muscle mass [in the 2nd part of the study, the PM training groups gained twice the amount of muscle the AM group did], while the E+S training order might be more beneficial for endurance performance development" (Küüsmaa. 2016). What is interesting, however, is that "training order and time seem to influence the magnitude of adaptations only when the training period exceeded 12 weeks (Küüsmaa. 2016; my emphasis) - that's an important observation from which I would like to segue right into the previously announced bottom line discussion of the few potential shortcomings of the study at hand.
Maybe, you don't have to choose between endurance and muscle gains! I am not sure if you looked close enough at Figure 2 to realize that, but the data from the study at hand shows that the PM cardio before weights group (eE+S) made both, the greatest CSA (muscle size) and Texh (exercise till you drop) gains of all groups... yes, I know the difference to the other PM group for CSA was as nonsignificant as the difference between the endurance gains in the AM vs. PM group, but overall that doesn't change the fact that the study at hand suggests that cardio before weights is the better way to go.
Does the study prove that everyone should do cardio first? Wtf!? Obviously not. Why do I even tell you about individuality and the influence of habits and training experience in the bottom line if you still think one study could prove everything you've been successfully for years wrong? Ah, and no, you don't have to start doing cardio and weights on the same day, if doing it on separate days works for you ;-)
Bottom line: I've already hinted at it at the top and in the the last line(s) of the main part of this article: compared to your average "Cardio or weights first?" and / or "AM or PM what's the best time to train?" experiments, the Küüsmaa study provides practically relevant outcome measures, unfortunately, it also provides evidence that its results may be subject specific and may not translate one-to-one from untrained beginners, as they were used in the study at hand to trained (semi-)professionals.

What does that mean? Well, if the influence of the time of the day (AM vs. PM) became significant only in the latter 12 weeks. That would suggest that (a) one's training experience and/or (b) the marginally increased training load determine the importance of AM vs. PM training - whether this relationship is linear, as in "the more training experience you have and / or  the higher your training volume, the more you will benefit from doing your workouts in the PM", however, requires future studies in better-trained individuals and with differences in training volume that go beyond the planned addition of one workout every other week that was used in the study at hand.

With that being said, the take-home messages of the study are still: (1) Do cardio first, if you want to increase your endurance performance, too; (2) Train in the PM (if you can choose freely and are not an extreme morning type) and benefit from a likely increase in size and a non-significant increase in 1RM gains; but (3) don't forget that our response to training may depend on (a) training experience (see previous elaborations), (b) habits and (c) individuality. If you find that doing (1)-(2) sucks for you, just return to what you've previously done | Comment on Facebook!
References:
  • Burley, Simon D., et al. "The Differential Hormonal Milieu of Morning versus Evening May Have an Impact on Muscle Hypertrophic Potential." PLOS ONE 11.9 (2016): e0161500.
  • Küüsmaa, Maria, et al. "Effects of morning vs. evening combined strength and endurance training on physical performance, muscle hypertrophy and serum hormone concentrations." Applied Physiology, Nutrition, and Metabolism ja (2016).
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