Catherine O’Brien

Are you a night owl or a morning lark? Most people tend to fall into one of two groups: morning person vs. night owl. It turns out that there is a name for these categorizations and recent research suggests that knowing your sleep type may be important when planning your exercise. Depending on what type you are, the time of day you are doing your workout could be affecting your quality of sleep and vice versa. Sleep quality is a huge factor in our athletic performance and prolonged periods of poor quality sleep will inhibit our workouts. Here we will examine how night owls respond to morning HIIT and how early risers respond to evening HIIT.

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Sleep Chronotype

Sleep chronotype is determined by circadian rhythmicity. The Morningness-Eveningness Questionnaire (MEQ) determines whether you are a Morning Type, Evening Type or Neither Type. Morning types go to bed and rise earlier and are most productive at the beginning of the day. They have more energy then and start to wind down their days and feel more relaxed and less productive in the afternoon. Evening types go to bed and rise later and are most productive later in the day. They have a slower start to their mornings and find themselves ramping and being more active later in the afternoon. Recently, researchers investigated how sleep chronotype may relate to one’s response to physical activity during the day. Specifically, does sleep quality differ based on time of workout and sleep chronotype? In order to test this, they measured sleep quality leading up to and following a HIIT (high-intensity interval training) workout. This was a randomized crossover design in which all participants, regardless of sleep chronotype, experienced both early and late exercise conditions. The study proves an interesting one as your quality of sleep can also affect how good your workout is. The correlation between the two is worth noting.

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Related Article: 5 Exercises To Improve Your Sleep

The Study:

A group of collegiate soccer players took the MEQ to determine sleep chronotype. (They weren’t informed of the results until study completion). Individuals categorized as Neither Type were excluded. Participants were randomly assigned to either Group 1 or 2. The study design is outlined below.

Week 1: Preliminary measurements, fitness testing

Week 2: First HIIT Session

Group 1 8:00 am HIIT

Group 2 8:00 pm HIIT

Week 3: Wash out – maintained a typical lifestyle without exercise

Week 4: Second HIIT Session

Group 2 8:00 am HIIT

Group 1  8:00 pm HIIT

The HIIT workout included a 10-minute warm up and concluded with a 3-minute cooldown. The session was a 4×4 model in which participants sprinted on a treadmill at 90-95% of max heart rate for 4-minutes and then recovered for 3-minutes. They repeated this sprint 4x.

Recoup Fitness Roller

Related Article: 4 Tips for Balancing Sleep & Exercise

Sleep activity was recorded via an Actigraph Actiwatch for 1-day before and 2-days after the HIIT sessions. Actigraphs measured Actual Time Asleep (AST), Actual Wake Time (AWT), Sleep Efficiency (SE), Sleep Latency (SL), Immobility Time (IT), Moving Time (MT), Mean Activity Score (MAS) and Movement and Fragmentation Index (MFI).

The Findings:

Baseline measurements showed no significant differences between participants in terms of age, height, weight, BMI, fitness level or sleep quality.

  1. For both Morning and Evening Types, morning workouts did not affect sleep quality.
  2. Morning Types, engaging in evening workouts resulted in reduced sleep quality (increased moving time, decreased immobility time, increased actual wake time). Since morning people are most productive earlier in the day, they found that they were having troubles winding down after the stimulation of an evening HIIT and it affected their ability to fall and stay asleep.
  3. For Morning Types, sleep quality was similar to pre-test levels 2 days after engaging in the evening HIIT workout suggesting the negative effects were not long lasting. They were able to resume previous sleeping patterns after the effects of their evening HIIT wore off.

The Takeaway:

So what does this mean for you? If you are a morning type, stick with morning exercise sessions whenever possible. If you do an evening workout, your sleep that night may suffer. The interference with restful sleep could also hinder recovery for morning person athletes as your body is using sleep time to recover your body from you the workout. Fortunately, the dip in sleep quality doesn’t seem to last long. Lucky for evening types, sleep quality isn’t affected workout time. If overall you are someone who has troubles sleeping regardless of workout, small changes in sleep duration, to the magnitude of two hours, can affect athletic performance over time. Whether other measures of performance such as endurance and muscular strength are responsive to small changes in sleep duration remains to be elucidated. If you are a morning person or an evening, the quality of sleep you get affects your workout and day to day endurance. You feel bogged down when you are not getting quality sleep and won’t be able to get the most out of your workout no matter what time you’re doing HIIT! Make sure you are addressing troubles sleeping and your workouts will benefit.

Still having trouble sleeping? Meditation can really help relax your mind and keep your stress levels in check. We recommend utilizing the Muse Headband, which is a great meditation aid that guides you to a calm mind. Melatonin is also a really great sleep aid.







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