RESEARCH: studies shared from 3 to 9 Apr 23

All the studies I've shared are available on the RESOURCES PAGE.

This week's quick summary:

• Intervals and cognitive function
• Restricting carbohydrate intake and its impact on physical activity
• Brain training and endurance performance
• Longitudinal haematological responses to training load and heat acclimation
• To nap or not to nap?

INTERVALS: High intensity and sprint interval training, and work-related cognitive function in adults

A previous study I shared showed that aerobic exercise training increases the size of the anterior hippocampus. This study looked at the benefit of intervals for cognitive function and work performance.

STUDY DETAILS

1. Mean quality scores were “fair-to-good” for acute and chronic training studies.
2. Eighteen from 36 studies evidenced significant improvements in aspects of cognitive function related to work performance (i.e., attention, inhibition, memory, information processing speed, cognitive flexibility, intelligence, reaction time, and learning).
3. Only four studies tested the impact of HIIT/SIT on cognitive function in a work-based setting (e.g., the office or home).
4. Based on these findings, we posit that the evidence base shows promise in support of the benefits of high intensity, short duration exercise for cognitive function in adults.
5. While there is promising evidence, particularly from acute training studies, to indicate that high intensity, short duration exercise benefits cognitive function in adults, there is very limited evidence of application in workplace contexts.

PRACTICAL TAKEAWAY

Running intervals are important for developing as an athlete, but there also appears to be a benefit for cognitive function. When I shared this study a few runners responded that they felt more focused at work after an interval session at lunch time so that adds some anecdotal support to this work. Overall, combined with the benefits for brain size that come from aerobic exercise, I would recommend including at least one interval session in a week's training to make the most of these cognitive benefits that derive from training.

NUTRITION: Restricting sugar or carbohydrate intake does not impact physical activity level or energy intake over 24h despite changes in substrate use

STUDY DETAILS

Restricting carbohydrates or sugar can be a strategy for weight loss or part of a train-low strategy to improve fat metabolism. In this study, the authors set out to determine "the effects of dietary sugar or carbohydrate restriction on physical activity energy expenditure, energy intake, and physiological outcomes across 24h".

1. Twenty-five healthy men and women consumed three diets over a 24-h period: moderate carbohydrate and sugar content (MODSUG=50% carbohydrate [20% sugars]); low sugar content (LOWSUG=50% carbohydrate [<5% sugars]); and low carbohydrate content (LOWCHO=8% carbohydrate [<5% sugars]).
2. Postprandial metabolic responses to a prescribed breakfast (20% EI) were monitored under laboratory conditions before an ad libitum test lunch, with subsequent diet and physical activity monitoring under free-living conditions until blood sample collection the following morning.
3. All diets resulted in similar mean rates of both physical activity energy expenditure and energy intake.
4. The LOWCHO condition elicited the lowest glycaemic and insulinaemic responses to breakfast but the highest 24-h increase in LDL-cholesterol concentrations, with no differences between the MODSUG and LOWSUG treatments.
5. When energy density is controlled for, restricting either sugar or total dietary carbohydrate does not modulate physical activity level or energy intake over a 24-h period despite substantial metabolic changes.

PRACTICAL TAKEAWAY

Reducing carbohydrate or sugar without reducing total calorie intake does not appear to affect energy expenditure or energy intake within the first 24 hours. Athletes aiming to use a train-low protocol do not need to worry about reduced physical activity due to compensation after reduced carbohydrate or sugar intake. Additionally, for athletes trying to lose weight, it is more important to focus on a calorie deficit rather than just reducing carohydrate or sugar to see any significant benefit.

TRAINING: Prior brain endurance training improves endurance exercise performance

Mental fatigue affects performance which is why I've shared studies in the past that show ways of tackling mental fatigue and the benefit of performance feedback in reducing mental fatigue. In this study, the authors looked at brain training prior to exercise to see if it would build resilience to mental fatigue and thereby improve endurance performance.

1. Brain endurance training (BET) describes the systematic repetition of mentally-fatiguing cognitive tasks designed to build resilience to mental fatigue (MF) and improve endurance performance.
2. The current study evaluated the effects of mental training before physical training (prior BET) on exercise performance.
3. During the pre-test and post-test sessions, participants performed a 5-min rhythmic handgrip task requiring the generation of as much force as possible, a 20-min 2-back working memory task, and another 5-min rhythmic handgrip task.
4. The BET group also completed 20-min cognitive training (2-back working memory task, incongruent colour-word Stroop task) before each submaximal exercise training session.
5. Endurance performance improved more following BET (24%) than physical training alone (12%). Compared to the control group, the BET group showed higher prefrontal oxygenation during the post-test exercise tasks.
6. Mental training before physical training improves endurance performance greater than physical training alone.

PRACTICAL TAKEAWAY

There appears to be a significant and worthwhile benefit from brain training before exercise to improve endurance performance. While it is possible to perform brain training in a controlled environment while exercising (such as during on an indoor trainer), this study suggests that the same benefits can be incurred by doing the brain training prior to endurance training.

When I shared this study on Twitter, I learned from some replies of the Rewire Fitness platform for brain training. I haven't had the opportunity to investigate this fully yet, but it appears to be a useful way to start brain training for athletes. It would also be possible to try creating a protocol using the Stroop task which can be found online.

HEAT: Longitudinal haematological responses to training load and heat acclimation preceding a male team pursuit cycling World Record

I'm particularly interested in heat acclimation both for the performance benefits and for adapting to conditions that may occur on race day. I have shared a broad range of protocols and research studies on this topic on my resources page. In this study the authors looked at the training, heat acclimation, and physiological metrics of world-class cyclists over a significant time period (9 months) which provides useful insights into the benefits of heat acclimation.

1. Haemoglobin mass (Hbmass) and concentration ([Hb]), plasma volume (PV) and blood volume (BV) were assessed in nine male track endurance cyclists (3 occasions per month) training in temperate conditions (247 to 142 days prior to the WR) to establish responses to differing acute (ATL) and chronic (CTL) training loads
2. In temperate conditions, CTL was associated with Hbmass and BV but not [Hb].
3. During HA, PV increased 8.2%, while Hbmass, CTL and ATL were unchanged.
4. Hbmass and [Hb] were associated with all performance outcomes, except V̇O2max.
5. Both CTL and ATL were associated with changes in PV, but HA was associated with increased PV and maintainenance of Hbmass without increasing ATL or CTL.
6. In practical terms, maintaining high CTL and high Hbmass might be beneficial for improving endurance performance.

PRACTICAL TAKEAWAY

Heat acclimation may be a useful means of adding training load without increasing training time or intensity. This could be particularly useful during a taper where an athlete wants to reduce training load, but maintain plasma volume to achieve an optimal performance. Athletes who are interested in heat acclimation can follow a few different protocols which I've shared before (phased approach to heat acclimation, short-term heat acclimation, heat alleviation strategies for Tokyo 2020).

SLEEP: To nap or not to nap? A systematic review evaluating napping behavior in athletes and the impact on various measures of athletic performance

This systematic review investigated the current research on napping and provides insights into best practice for napping.

1. Napping may be beneficial for a range of outcomes that benefit athletes (eg, physical and cognitive performance, perceptual measures, psychological state and night-time sleep).
2. In addition, napping presents athletes with the opportunity to supplement their night-time sleep without compromising sleep quality.
3. Athletes may consider napping between 20 to 90 min in duration and between 13:00 and 16:00 hours.
4. Finally, athletes should allow 30 min to reduce sleep inertia prior to training or competition to obtain better performance outcomes.

PRACTICAL TAKEAWAY

There is a benefit to napping and athletes who have the opportunity to do so should follow the guidelines found in this review (20-90' between 13h00 and 16h00). For athletes who cannot regularly nap, there may be benefit for sleep extension in race week especially when preparing for ultramarathon races. My recommendation would be to nap when it's possible and for athletes who are training at a high level to include naps every day.