Coach Tip Tuesday: An Undervalued Training Consideration: Time of Day

Posted On:
Tuesday, June 7, 2022
Updated On:
Tuesday, July 18, 2023
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A silhouette of a woman running with the sun in the background!

When training for a race, the things to consider as you prepare for race day can be seemingly endless.  There’s gear, nutrition, hydration, recovery, workout structure, training plans - just to name a few!  While all of those things are very important, there’s one training consideration that I see devalued over and over and over again week after week after week: Time of day.

Why Does Time of Day Matter?

Taking note of the time of day that you will be racing is incredibly important.  Time of day impacts so many things - weather conditions, nutrition/hydration status, and fatigue levels are just three of those.  The idea of “nothing new on race day” is pretty well-known, but most athletes (age-group athletes especially) interpret this as meaning nothing new as far as gear, nutrition, or hydration goes.  And while that’s true, I am here to present the case that you cannot race at a new time of day and expect the same results you’ve been getting in training if you’ve been training at a different time of day.

A lot of races do take place at the beginning of the day.  But many races do take place later in the day.  Triathlons - no matter the distance - always end up taking place later in the day; even if the swim starts early, the bike and run are starting later just by virtue of how a triathlon is structured.  This is most especially true in IRONMAN triathlons due to their length; the bike won’t start until the middle of the morning and the run doesn’t start until the early to mid-afternoon for the majority of athletes.  However, even stand-alone cycling or running events can (and do!) take place later in the day depending on the race (Rock ‘n’ Roll Las Vegas - I’m looking at you).

As such, it’s really, really important to consider the time of day that you will be racing.  If you are training for a race where you will be racing later in the day and you always get your key workouts completed early in the morning before the sun is really up or before the conditions that may be in play on race day are a factor, you will never (and I mean never) reach your potential.  (Don’t make the mistake of thinking I’m being melodramatic here; this is the truth, even if it’s hard to hear. :) )

For example, if you are training for an IRONMAN (or any long-course triathlon, really) and you train like that, you will never (and I mean never) reach your potential in that type of race because your body will not be properly prepared for the demand being placed on it at that time of day on race day.  (I should have included this in my post about reaching your potential in an IRONMAN, but since this is a concept that extends to more than just IRONMAN racing, I decided to give it its own post. :) )

Weather Acclimatization

Completing key workouts (such as your longest workouts of the week) at the same time of day that you will be executing your race allows you to acclimatize as-needed to relevant weather conditions (such as sun/UV exposure, heat, humidity, and wind).  Getting your body properly acclimatized to heat is especially important; it takes a minimum of 10-14 days of continuous exposure to elicit the physiological changes needed to handle heat.  (10-14 days is the minimum; it actually takes 14-21 days in total, but 10-14 days definitely starts the process.)

When you acclimatize to the heat, two very important changes occur in your body.  The first is that your total blood volume increases.  (Specifically, your plasma (the watery part of your blood) and your red blood cell volumes increase.)  This enables your body to improve the blood flow to your skin and muscles as well as keep your heart rate, skin, and body temperatures lower, which enables you to exert yourself more in terms of time and intensity.  The second adaptation is that the composition of your sweat changes so that you lose fewer electrolytes as you sweat (up to 50% fewer!).  This enables your body to retain them and use them for muscle function.  

If you’ll be racing at a later time of day, your nutrition/hydration status is going to be much different than if you are racing relatively quickly after waking up (i.e. within a few hours of waking up).  Asking your body to put forth a hard effort later in the day will require you to dial-in very specifically on what fueling and hydration works best for you over the course of a day.  Some athletes have stomachs of steel and can handle anything they want to food and hydration-wise over the course of a day.  Other athletes have very sensitive GI systems and need to be very mindful about what they consume in the time period leading up to a workout or race.  Thus, training at the time of day that you will be racing will allow you to practice these important elements.

Adaptations to exercising in the heat cannot be gained any other way than frequently and consistently training at a particular time of day.  The same is true for nutrition over the course of a day.  That continuous exposure is what forces the body to physiologically adapt to the stimulus you are exposing it to.  6:30 a.m. just won’t cut it if what you’re doing in your race won’t be starting until 11:00 a.m. or later. 

Discomfort Yields Opportunity

One of the biggest pushbacks I get when I mention this concept is that it is uncomfortable - mentally, physically, or both.  And yes, that can definitely be true.  But while this may seem like an obstacle, it’s really an opportunity.  It’s an opportunity to train your body to adapt the way it needs to to support your goals.  It’s an opportunity to embark on some mental training to help prepare your mind to handle hard and challenging conditions.  In short, it’s an opportunity to grow - in a number of ways.

It’s true that age-group athletes are people living very busy lives outside of sport, and so it may not be logistically possible to train at the same time of day that one’s goal race is taking place.  If this is true, it becomes necessary to be honest and realistic about expectations for race day performance.  While mindset and mental training is incredibly important, no amount of positive thinking can overcome a lack of appropriate and necessary physiological adaptations.  If you are unable (or unwilling ;) ) to train at the same time of day that you will be racing, you need to modify your expectations for your race day performance to be in-line with how you have actually trained. 

The Bottom Line

The specificity here matters and it’s the only thing that will appropriately prepare you for your race and goals.  You can do it, or you can not do it, but it doesn’t change the fact that this is what it takes.  Don’t be part of the majority that doesn’t value (or even consider!) how important Time of Day is in training.  Take a good look at your training schedule and habits and see if you can’t accommodate a few adjustments to optimize your training Time of Day to help you reach success on race day.


Coach Laura Henry

Laura Henry is a Syracuse, NY-based coach who is a USA Triathlon Level II Long Course and Level II Paratriathlon Certified Coach, USA Cycling Level 2 Certified Coach, VFS Certified Bike Fitter, and has successfully completed NASM's Certified Personal Trainer course. Coach Laura is passionate about helping athletes of all ability levels reach their goals and has coached many athletes to success.

She can be reached at

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