Does Food and Sleep Effect Exercise This Much?!

Just before we started the session, Brittany said she got hardly any sleep and she hadn't eaten much of anything that day (she found a guy). So what. What has lack of sleep and lack of food got to do with exercise?

high intensity training

What do people think when they walk into a gym and "workout" without a thought of what their body has been through, what it needs, or if it can even handle the workout?

They do it anyway – to the detriment of their body. The workout, in essence, is worse than not doing any good, it may make everything a lot worse.

So we take a look at Brittany on a Wednesday. Her HIIT workout was a 20 second burst, 4 intervals. She did not tell me anything other than her usual, dating a guy and probably going to get married this year and that she is motivated to trim up. There’s nothing wrong here.

So we began the session Wednesday as usual. Each of her intervals  are either in the orange zone or red zone; her lowest high heart rate was almost 130 and her highest high 171. Take a look here…

The Best Exercise

However, she showed up Friday afternoon close to the same time with a different story. She sat on the Myoride exercise machine and the first thing she said was that she barely had any sleep Thursday, the night before and that she hadn't eaten anything all day. What could have happened? I wasn’t that interested in what had happened, only interested in what was going to happen for this session.

She started out full blast in her first 20 second burst but just as quick as she started, she slowed. She struggled. The first 20 seconds seemed to her like forever. The angst was all over her face. She did not let that deter her. She struggled through the next interval and the next. I saw what was going on in real time - her heart rate was struggling right along with her.

This is her heart rate profile for Friday, the disaster-session…

The Best Exercise


Wednesday - all four bursts were high, either in the high orange zone or in the red zone. Her maximum heart rate reached 171 bpm. I won't discuss any other factors but only to show you how her heart rate responded to the burst intervals.

Friday - all four bursts were low, two didn't make it out of the yellow zone so she didn't crack 120 bpm in these. Her maximum heart rate reached 138, far less than the previous session. And she was completely exhausted at the end of the fourth interval.


One of the important factors about exercise is the personal profile of the exerciser. If the person has had a bad night or bad previous day then maybe they should not exercise or their workout should be minimal. Is this taken into account very often?

Exercising when the body is not capable of the exercise stress is not a good idea and may in fact, be a detriment to continued progress in fitness or performance. And more importantly, the exercise may be worsening their body function during the exercise event. If a person continues exercising through the stresses of the workout they are causing catabolic damage.

If a person is not feeling well and is thinking about exercising, how can you:

  1. Show evidence that they should not begin?

  2. Show evidence during the workout that they should stop?

The answer to both of these questions is the same. The question is, what biomarkers can be used to gauge stress or the parameters of progress that you can follow and make wise decisions with?

Like Brittany. She said before we even began that she had just a few hours of sleep and hadn't eaten anything all day. She had a sense that this exercise session was different before she even started. Yet, she wanted to continue because she had a goal in mind to: get in shape, lose several pounds, improve her %body fat and improve her BMI scores. But more importantly to her, she had found a guy and this fact clouded any rational thinking.

I was all game to put her through the entire HIIT session but I was cautious because of what she said. And we see the results of her heart rate monitor and her HIIT sprint intervals. They were not normal for her. I was observing each of these intervals in real time and could tell her output was not typical.

I would not have believed that her lack of sleep and lack of food would cause such responses. Because of this I'm in the process of monitoring even more biometrics during a HIIT session and recording the important information such as:

  1. Asking how they're feeling before we begin a session. A person will offer information that may preclude them from engaging in an exercise session. Will they listen to themselves?

  2. Taking a forehead temperature with an infrared thermometer. This is going to take awhile to calibrate. First we need to establish a baseline. Then, if the forehead temperature is either higher or lower than baseline we have a conversation about what may be going on and if we wish to continue.

  3. Heart rate monitoring. If the heart rate falls well below normal like in this case, when no other factors have changed (intensity, duration, velocity) then the user and I have a conversation.

  4. Rate of Perceived Exertion (RPE). This is a subjective question that the exerciser will be asked at the end of the session; "on a scale of 1-10, how difficult was this session?" While this is after the exercise, it won't be helpful for the current session but may offer information for the upcoming session. Such as, if the RPE is the same from session to session, it may be time to alter one of the variables (Intensity, duration, velocity).

  5. Heart rate variability. This is a newer biometric that will shed a light into the influence of the autonomic nervous system and its response to stress.

Monitoring biometrics is only going to improve. And with it, so shall the helpful influence they will have on the maintenance of health or the progression of human performance.

Even though Brittany told me she wasn't feeling great she wasn't going to not exercise and I let her without a lot of validity as to why she shouldn't. But with all the biometrics pointing to why she shouldn't exercise, she probably wouldn't listen to them and me anyway. Her goal was the guy and nothing was going to stand in her way.