I had a question from Benson a while back that caught my interest. I haven't done much actual research on the topic and what I knew was just from anecdotal evidence. So I looked into the issue a little deeper.
The question deals with workout timing. Specifically, when is the best time to train (for endurance sport/triathlon)? In Benson's case, as with many full-time employees or people with jobs, school, etc, it's either train early morning right out of bed before breakfast OR late afternoon/evening after work. It's a very interesting topic that could affect performance on race day, or could even affect your susceptibility to injury.... let's look at the deets...
Here are the pros and cons to each (AM = hop out of bed and go, usually without food; PM = after work, late afternoon/evening):
AM TRAINING PROS:
1. This is close to the time you'll be racing (if we're talking triathlon and most endurance events), so your body will be familiar with exercise at the right time of day for the race and your circadian rhythm will adapt to this as well.
2. You become a better fat burner/more efficient with fuel utilization. You're exercising in a fasted state assuming your last meal was dinner or a snack the night prior, so this teaches your body to become more efficient with burning fat as fuel. Great if your goal includes weight loss too.
3. Gets your body revved up for the day. You increase your metabolic rate and will continue burning more calories as compared to no morning workout. You might even be more productive during the day's work!
4. You get it done and taken care of, so you don't have to worry about work or life issues interfering later on, i.e. those things that could end up canceling the training session altogether.
AM TRAINING NEGATIVES
1. Your BBT (basal body temp) is lower when you first wake up, meaning your body is cold, stiff and lacking ideal mobility/flexibility. That makes it essential to get in a long, quality warmup to get the body temp up and muscles warm and lose. Failure to do so can make your more susteptible to tweaking, pulling or injuring something, or just have crappy form/technique. No bueno.
2. If you train pre-breakfast you're exercising in a fasted state and therefore might not be able to reach higher intensities or last as long, i.e. quality of workout suffers. If you incorporating nutrition during (gels, etc) that may help, but even then you don't have that "base meal" of 500+ breakfast calories to keep you going.
3. Nutrient timing post-exercise is extra vital. This isn't necessarily a bad thing, but you do have to be more careful to ensure that you get in adequate calories RIGHT AFTER you finish the workout to start the recovery process and prevent your body from going into a catabolic state.
4. Rising and working out so early may cause that major afternoon slump and/or state of hunger in which you need a nap or start binging on snacks, especially if you're post-workout meal wasn't adequate. Be careful of this! And don't grab for that 5-Hour Energy bottle ;)
PM TRAINING PROS:
1. Body temp (BBT) is up by 1-2 degrees (it peaks in the afternoon 2-5 p.m.ish) so you're warmer and muscles, connective tissues are in a good state for working out. Thus, you may perform better and be at lower risk of injury (as opposed to working out "cold" in the AM). Plus, you've likely eaten a couple meals so you'll have good energy and glycogen availability for increased endurance and less bonking potential/running on empty.
1a. Muscle strength and endurance may be at its peak so you kick ass.
1b. Warming up is still important but not as crucial as it is first thing out of bed.
2. Afternoon workouts can improve sleep -- fall asleep faster + better quality sleep -- as long as it's not too close to bedtime, which can leave you feeling too pumped up and unable to get to sleep.
3. If you're free from work and the day's obligations, you might have more time than in the AM so you can get in a well-rounded workout. Thus, there's a good chance you'll get a better quality workout than doing a rushed AM session. Quality rules all!
PM TRAINING CONS:
1. This is not the time of day when you'll be racing (generally), and if you only train in the later hours, doing an AM race may shock your system and negatively affect race performance. (Specificity is key!)
2. GI issues? Some people don't do as well training after eating meals and snacks throughout the day. Most commonly this is seen in running. (I've suffered from this on occasion.)
3. More likely to ditch it? Motivation levels may be lower because you're tired from a long day at work or whatever, and all you want to do is rest/eat/watch the game/have a beer or you're still busy with other stuff so a) you speed through the workout and it's not as quality or b) you hurt yourself for being careless/rushing or c) you might end up skipping the workout all together.
I know this is shocking, but the real answer: It comes down to personal preference. There's no overwhelming scientific data to prove one time is better than the other, except to say the science tells us it's highly individual: Certain people do better at certain times of day based on their circadian rhythms/biorhythms. The best time of day for you also depends on your goals: weight loss, just fitting it a workout at all, consistency, time/duration/intensity of the session, race specificity, etc.
I recommend four things:
1) Experiment with timing. Try the AM thing at varying intensities, and then do the same with PM. See what happens both physically and mentally, compare performances, etc.
2) Based off #1, generally do your KEY workouts at the time during which your body feels most "on" and peppy, and when motivation is the highest! If you have to train 2x a day, do your secondary workout during your "off/blah" time.
3) No matter your best time, schedule some morning workouts around the time your race will be starting so you're not totally shocked on race day. This can include the whole production of a super-early pre-workout breakfast at least 1-2 hrs prior to exercise to ensure that all goes well GI-wise, etc.
4) Another alternative: Do lunchtime workouts!!! I am a huge fan of lunchtime training (before you eat lunch that is). You're likely to have good energy from brekkie/mid-morning snack, you haven't hit the mid-afternoon slump, and you're probably on a time limit so you'll go hard to get in the most bang for your buck. The reward: a big lunch right after and extra energy for the rest of the day!
As for me...
Personally, I truly enjoy the occasional first-thing-in-the-morning workout where I hop out of bed and go. It's really a great way to start the day. But I can usually only last for an hour in that unfed state, and though I can attempt high-intensity stuff, it's not as good as when I'm fueled from a meal.
My ideal/typical workout situation: Mid-morning training. I get up at 6 a.m. and start working, eat a big breakfast at 6:30-7 a.m. and let that settle while working more, then I get going around 9-10 a.m. before lunchtime. Usually have some gel/nutrition during depending on workout length/intensity. Thankfully, with my job(s), I have the luxury of starting training mid-morning on most days so I don't have to eat brekkie at ungodly hours:)
I do evening workouts, too, especially since two-a-days are common. I can get evening sessions done in decent fashion and feel good, but generally as the hours in the day go on, my motivation levels tend to drop, especially if I've already done a morning workout. Overall, I don't really prefer PM workouts and truthfully getting started at 4-7 p.m. is hard for me, so I usually make those workouts my "secondary" workouts.
All that said, I do my best to get in the training that needs to get in, no matter what time of day.
*Last note: I'm going to continue looking for scientific studies on this subject and see if I discover anything more worth sharing.
So what works best for you as far as training and time of day? Any thoughts and insights on your ideal time of day to workout? Is it dictated by your other life duties or do you call the shots?