🔥Upside Guest Writer Series: “Impact of Time of Day on Athletic Performance”, By Arthur Weltman, PhD, Professor of Kinesiology, Professor of Medicine, University of Virginia

Aug 18, 2022

This week our guest writers is Arthur Weltman, PhD , Professor of Kinesiology, Professor of Medicine, at the University of Virginia.

This week Arthur, in his piece entitles “Impact of Time of Day on Athletic Performance”, he gave us his insights on a study that he conducted on the impact of time of the day on athletic performance.

Title: Impact of Time of Day on Athletic Performance

By Arthur Weltman

Before we discuss our study focusing on the impact of time of day on athletic performance , let’s go over a couple of definitions.

What are Circadian Rhythms?

According to the NIH “Circadian rhythms are physical, mental, and behavioral changes that follow a 24-hour cycle. These natural processes respond primarily to light and dark and affect most living things…”, including humans. One prominent example of a circadian rhythm is the light dark rhythm, where you sleep at night and are awake during the day.

Biological Clocks and Circadian Rhythms

Circadian Rhythms are regulated by biological clocks which are the body’s natural timing device. Biological clocks are composed of specific proteins that interact with cells within nearly every tissue and organ within the body.

The Brain has a Master Clock

A master clock in the brain coordinates all the biological clocks in a living thing, keeping the biological clocks in sync. In humans, the master clock is a group of about 20,000 neurons that forms the suprachiasmatic nucleus, located within the hypothalamus part of the brain.

Circadian Rhythms and Exercise

Skeletal muscle has an extensive network of genes that control its molecular clock and data suggest that dysregulation of this molecular clock can lead to deleterious metabolic consequences and impaired physical performance. Several studies show that exercise modifies the rhythm of the skeletal muscle biological clock, however the timing of exercise to favorably modify the rhythm of the clock machinery in skeletal muscle is not fully known.

Athletic Performance and Circadian Timing. More world records are broken by athletes competing in the early evening

Although the interaction between the health benefits of exercise and optimal diurnal timing have not been extensively studied, there is a body of emerging data that exist with regard to diurnal training and exercise performance.

For example, more world records are broken by athletes competing in the early evening, disruption of diurnal rhythm by eastward trans-meridian travel has a greater negative impact on performance and indicator of fatigue than westward travel.

Resistance exercise/training appears to be the most susceptible to changes in diurnal timing with peak strength/force almost always highest in the afternoon and evening with the average difference being somewhere around 8%.

Similarly, high-intensity exercise demonstrates a similar daily pattern of performance as observed with resistance training, with peak performance in the afternoon and evening and diminished performance in the morning.

Although chronic training studies are limited, two well controlled studies indicate that training in the evening resulted in greater adaptations than training in the morning [Kuusmaa, M. et al. Effects of morning versus evening combined strength and endurance training on physical performance, muscle hypertrophy, and serum hormone concentrations. Appl. Physiol. Nutr. Metab. 41, 1285–1294 (2016); Sedliak, M. et al. Morphological, molecular and hormonal adaptations to early morning versus afternoon resistance training. Chronobiol. Int. 35, 450–464 (2018)]

Training using Time of Day as a Factor to Maximize Performance

As mentioned above, time of day can be a key factor that influences the optimization of athletic performance. However, Intercollegiate coaches oftentimes hold early morning strength and conditioning training sessions for a variety of factors including convenience. As mentioned few studies have specifically investigated the effect of early morning vs. late afternoon training on performance indices of fatigue. This is athletically important because circadian/ultradian rhythms, player readiness, and alterations in sleep patterns can affect training ability and may be affected by time of day. We conducted a study that examined the effects of morning vs. afternoon strength and conditioning training on an acute performance index of fatigue, player readiness, and self-reported sleep quantity in a group of highly competitive intercollegiate basketball players. In addition, we matched training sessions for player load (PL) and duration to isolate the effect of time of day on player readiness and performance outcomes. We hypothesized that afternoon training sessions would be associated with increased levels of performance, player readiness, and increased quantity of self-reported sleep (Heishman et al. Comparing performance during morning vs. afternoon training sessions in intercollegiate basketball players; Journal of Strength and Conditioning Research, 31: 1557-1562, 2017).

Ten elite male NCAA Division 1 basketball players (age 20.9 + 1.2 years, height 188.0 + 7.9 cm, mass 100.8 + 9.2 kg, body mass index 25.2 + 0.6 kg.m-2, and body fat 10.3 +2.2% [BodPod, Life Measurement Instruments, Concord, CA, USA]) were included in this study. Each athlete met individually with the Athletic Department Sport Nutritionist and was provided with nutrition guidelines designed to enhance performance. Before each strength and conditioning session, each athlete was provided a drink that contained a combination of Gatorade, maltodextrin, and amino acids (amino acids included per athlete’s ability to purchase independently). Each drink varied between athletes based on the nutritional needs of the individual (determined by the Sport Nutritionist) but did not vary within an individual athlete.

Data were collected over the 5-week preseason training period just before the beginning of competitive season practice. During this time frame, the National Collegiate Athletic

Association (NCAA) allows for 8 hr/wk of strength and conditioning activities (16 sessions total) and 2 hr/wk of basketball-related activities. All basketball-related activities (e.g., skill development, practice etc.) were performed in the afternoon, whereas strength and conditioning sessions were performed either in the morning or in the afternoon based on facility availability and class schedules of the student athletes. For the men’s basketball team, the first 8 strength and conditioning sessions were performed in the afternoon and the last 8 strength and conditioning sessions were performed in the morning.

We measured the following parameters:

Internal Load Monitoring was measured using Omegawave technology to evaluate each athlete’s functional state of readiness before training. Each athlete was provided a personal mobile unit for testing and Omegawave measurements were made upon arrival to each strength and conditioning session.
External Load Monitoring was measured using Catapult Optieye S5 units. Athlete monitoring and load accumulation were collected during all basketball-related training sessions.
Sleep was measured using a subjective sleep questionnaire and was defined as the hours from bedtime to wake time.
Time of Day. Athletes performed strength training sessions in small groups. Morning strength training sessions took place between 0700 and 0900 hours. Afternoon strength training sessions took place from 1345 to 1600 hours. Basketball skill development activities always took place in the afternoon, with a start time ranging from 1500 to 1700 hours.
Performance Assessment. Power output was determined by the maximal countermovement vertical jump (CMJ), as it is known to identify neuromuscular fatigue.

Subjects performed testing immediately after the Omegawave assessment before their strength training sessions 3 times per week. A standard warm-up was performed before each testing session. Subjects started tall with hands akimbo and performed a CMJ to their maximal ability. Two measurements for vertical jump were taken via The Just Jump System. The highest height achieved for the day was defined as maximal vertical jump.

Table 1 (see below) shows the difference in morning vs afternoon training performance whereas Table 2 (see below) shows morning vs afternoon sessions with matched training intensity and duration during the previous exposure.

Countermovement Jump (CMJ), Power Output (Power), Overall Readiness (Overall), CNS Readiness (CNS), PlayerLoad™ (PL), and Duration when comparing the morning training value to the afternoon training value with matched training intensity during the previous exposure. Data are mean ± SEM.

The major findings of our study were (a) decreased performance during morning compared with afternoon sessions when PL and duration were matched, (b) reduced self-reported sleep associated with morning training sessions, and (c) decrements in performance during morning training despite no differences in player readiness.

Practical Applications

The results of this study are consistent with the aforementioned discussion of Circadian Rhythms, Biological Clocks and Diurnal Timing, and have several practical applications for designing training. Athlete performance is compromised during morning training. In addition, the reduced quantity of sleep associated with early morning practice, although not necessarily affecting player readiness, is associated with impaired performance. Strength and conditioning and sport coaches should consider avoiding morning training sessions and practices, as athlete performance adaptations can be compromised during this time of day.

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