Interesting article findings. I have more challenges getting my HR up in the morning. I wonder if cortisol/adrenal function plays a role also.
There is a normal curve of hormonal function noted with ASI (Adrenal stress index testing) that shows the highest circadian levels of cortisol with am (yes, mornings) and tapering as the day progresses. This does not appear to take into account exercise but is normative reference points based upon a 4x/day sampling of saliva and corresponding cortisol levels.
So, is there a relationship between elevated cortisol levels and depressed HR with exercise?
There are a variety of really good studies on this topic. I put up a post back in forum 3.0. Basically, our bodies perform about 5% better in endurance tasks in the late afternoon/early evening vs early morning. This is true not only in terms of HR, but also in terms of FTP, maximal force, etc. It seems hardwired into us and while there is almost certainly person to person variability appears to affect all of us to about the same degree. Even folks who consider themselves "morning people" can perform relatively better objectively vs themselves on afternoon efforts vs early AM. The studies were well controlled for wakefulness, etc. Doesn't mean exercising in AM vs PM is better/worse/or indifferent just that you will be faster in the PM than in the AM. Among the more interesting statistics backing this up is that essentially most all endurance world records, particularly in track and swimming, have been set between 4-6PM. Theories abound as to the reason for the variation, including cortisol, etc; but bottom line is that no one really knows what causes it. The good news is that your competition is just as susceptible to it as you are. It also doesn't seem to be something you can "train away." In that the delta between AM and PM performances seems to persist despite gains in fitness or changing the time of daily workouts.
Bottom line is train when its best for you scheduling wise and don't worry about it too much.
“Most components (strength, power, speed) of athletic performance are worst in the early hours of the morning,” he wrote in an e-mail message. “Ratings of perceived exertion during exercise have generally been found to be highest in the early morning.”
Amen. My 5:30 am weekday workouts have a much higher RPE than even the ones that start at 9 on the weekend. If I get up really early on the weekends, and have several hours before going out the door, the workout always seems to go better. I have quietly thought that was true for me for the past couple of years. Might actually be so. Interesting article.
The study makes sense to me. I'm not always awake enough in the morning to get my heart rate up. Also, studies have long shown that folks who run in the morning are more likely to be injured than those who run in the evening because the body temperature is lower and you just aren't as warmed up as you are when you've been up all day. But regardless, my training schedule is often driven by things I can't control...e.g., Masters Swim is M-W-F morning. r/Paul
I would also guess that if we test FTP and vDot in the evening on loads of carbs/caffeine then it makes sense that hitting our numbers in the early morning might be a challenge. Of course we all race in the morning so I would think that our final test prior to an "A" race should be a morning test. I know I'm splitting hairs but as Rich would say: "I'm just sayin...".
Thank you for sharing this article! I commute into New York city every day for work and as such roust myself out of bed at 4:30 am to get on the bike at 4:45 or so. Many mornings after my first interval at 95 to 100% z4-z5 power I struggle in my second and third intervals to stay even close to 95%. Then on the weekends I'll do an 8 am computrainer session and post an average power threshold 20% higher than what I'm doing during the week - daylight is definitely my friend!
Comments
Interesting article findings. I have more challenges getting my HR up in the morning. I wonder if cortisol/adrenal function plays a role also.
There is a normal curve of hormonal function noted with ASI (Adrenal stress index testing) that shows the highest circadian levels of cortisol with am (yes, mornings) and tapering as the day progresses. This does not appear to take into account exercise but is normative reference points based upon a 4x/day sampling of saliva and corresponding cortisol levels.
So, is there a relationship between elevated cortisol levels and depressed HR with exercise?
Vince
There are a variety of really good studies on this topic. I put up a post back in forum 3.0. Basically, our bodies perform about 5% better in endurance tasks in the late afternoon/early evening vs early morning. This is true not only in terms of HR, but also in terms of FTP, maximal force, etc. It seems hardwired into us and while there is almost certainly person to person variability appears to affect all of us to about the same degree. Even folks who consider themselves "morning people" can perform relatively better objectively vs themselves on afternoon efforts vs early AM. The studies were well controlled for wakefulness, etc. Doesn't mean exercising in AM vs PM is better/worse/or indifferent just that you will be faster in the PM than in the AM. Among the more interesting statistics backing this up is that essentially most all endurance world records, particularly in track and swimming, have been set between 4-6PM. Theories abound as to the reason for the variation, including cortisol, etc; but bottom line is that no one really knows what causes it. The good news is that your competition is just as susceptible to it as you are. It also doesn't seem to be something you can "train away." In that the delta between AM and PM performances seems to persist despite gains in fitness or changing the time of daily workouts.
Bottom line is train when its best for you scheduling wise and don't worry about it too much.
That's what I'm hearing (reading) in this thread.
From the article:
“Most components (strength, power, speed) of athletic performance are worst in the early hours of the morning,” he wrote in an e-mail message. “Ratings of perceived exertion during exercise have generally been found to be highest in the early morning.”
Amen. My 5:30 am weekday workouts have a much higher RPE than even the ones that start at 9 on the weekend. If I get up really early on the weekends, and have several hours before going out the door, the workout always seems to go better. I have quietly thought that was true for me for the past couple of years. Might actually be so. Interesting article.
The study makes sense to me. I'm not always awake enough in the morning to get my heart rate up. Also, studies have long shown that folks who run in the morning are more likely to be injured than those who run in the evening because the body temperature is lower and you just aren't as warmed up as you are when you've been up all day. But regardless, my training schedule is often driven by things I can't control...e.g., Masters Swim is M-W-F morning. r/Paul
Vince
Thank you for sharing this article! I commute into New York city every day for work and as such roust myself out of bed at 4:30 am to get on the bike at 4:45 or so. Many mornings after my first interval at 95 to 100% z4-z5 power I struggle in my second and third intervals to stay even close to 95%. Then on the weekends I'll do an 8 am computrainer session and post an average power threshold 20% higher than what I'm doing during the week - daylight is definitely my friend!