Most of us don't really get to choose whether we work out in the morning or the evening. Mr. Willoughby, your boss, is the one that gets to make that decision and if he wants your butt in that ergodynamically piss-poor chair from 8 to 5, well, you're likely stuck with working out in the evening.
Hell, the only people who really get to choose are those that lie at either end of the economic scale, meaning rich bastards and unemployed bastards. Both are captains of their fate, one the captain of a really nice, 150-foot fate with a helicopter pad, and the other the captain of a little faded, rubber dinghy of a fate, but captains nonetheless. They both get to work out whenever the hell they want.
But let's say you got to make a choice. Which would you choose, the early workout or the late workout? More importantly, which does science say is the better choice? Some Finnish scientists decided to figure it out and they say that working out in the evening is the better, long-term choice for muscle.
The scientists rounded up 42 healthy men who weren't lifters and devised a training program for them that consisted of a combination of strength exercises and endurance exercises.
The purpose was to see whether time of training (morning or late afternoon/evening) and order of training (strength exercise first or endurance exercise first) made any difference on outcome. The men were divided into 5 groups:
- A group that worked out between 7:30 and 10:00 in the morning and did cardio before weight training.
- A group that worked out between 7:30 and 10:00 in the morning and did weight training before cardio training.
- A group that worked out between 5:30 and 8:00 in the evening and did cardio before weight training.
- A group that worked out between 5:30 and 8:00 in the evening and did weight training before cardio.
- A group that did not exercise at all, preferring instead to frolic in sun-kissed fields of wheat.
The weight lifting program involved leg presses, leg curls, leg extensions, dumbbell flies, military presses, lat pulldowns, curls, triceps pushdowns, and crunches. The workouts became progressively harder, using more weight and more weekly training sessions.
The cardio program consisted of 30-50 minute sessions of either steady-state cardio or high-intensity interval training.
Subjects were assessed repeatedly for 1 RM in the leg press and time to exhaustion in an incremental cycle ergometer test. The scientists also measured the cross sectional area (CSA) of the subjects' vastus lateralis and took repeated measurements of serum testosterone and cortisol concentrations.
Cortisol and testosterone levels didn't change, regardless of time of workout or exercise order.
As for whether morning or evening workouts were better for muscle size, it didn't matter at all, but only for the first 12 weeks. After that period, it mattered a lot. The evening workout led to greater gains compared to the same program done earlier in the day.
Furthermore, as far as building up stamina through cardio, the subjects made more progress when they did their endurance training before their strength training.
The sequence didn't seem to affect strength training, though. Subjects who lifted weight first and then followed it up with cardio gained just as much muscle as subjects who did cardio first and then followed it up with lifting.
Raw novices, as usual, get off scot-free; they can work out whenever they want and still make progress.
However, after about 12 weeks, it looks like evening training is the best. And, if you like to combine endurance training with strength training, it only matters (according to the parameters of this study) which you do first if you're interested in focusing on cardio.
In that case, do cardio first. If strength and bodybuilding is your concern, it doesn't matter whether you do cardio first or strength training first.
Unlike most studies, the researchers didn't have any guesses as to why things turned out the way they did in this study: "The mechanisms for these dissimilar gains after morning and evening combined training, however, are unclear."
- Küüsmaa M et al. Effects of morning versus evening combined strength and endurance training on physical performance, muscle hypertrophy, and serum hormone concentrations. Appl Physiol Nutr Metab. 2016 Dec;41(12):1285-1294. PubMed.