RESEARCH: studies shared from 27 to 31 Mar 23

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

This week's quick summary:

• Nutritional elements in sleep
• Training characteristics of elite cyclists
• Hydration state on thermoregulation during an ultramarathon
• Monitoring heart rates to evaluate pacing
• Dietary observations of ultra-endurance runners

NUTRITION: Nutritional elements in sleep

Sleep is critical for multiple functions of the body (search for "sleep" on my resources page to see studies on sleep and recovery, muscle protein synthesis, testosterone levels, and more). In this article the authors set out to explore the impact of various nutritional factors on sleep. My notes and highlights from the article are below.

STUDY DETAILS

1. Chrono-nutrition: closer proximity of dinner time to sleep time, especially if less than two hours, leads to poor sleep quality.
2. Melatonin-boosting foods: significantly improves sleep quality and decreases sleep onset latency.
3. Melatonin-boosting foods: fresh tart cherry juice effectively reduced sleep latency and improved insomnia.
4. Serotonin: consuming two kiwifruits an hour before bedtime improved serotonin levels, thus helping to increase total sleep time and sleep quality.
5. Tryptophan: consumption of tryptophan-rich food items like cereals and a high-protein diet containing tryptophan can assist in improving sleep outcomes.
6. Fatty fish and seafood: a high intake of fish and vegetables has a positive effect on sleep. Fatty fish is rich in vitamin D and omega-3 fatty acids.
7. Milk: the intake of enriched milk and dairy products leads to anti-inflammatory and antioxidant changes in the brain-gut-microbiome axis and thus promotes good sleep.
8. Caffeine: shown to reduce total sleep time by more than one hour, even when consumed six hours before bedtime/
9. Alcohol: alcohol consumption within four hours of bedtime leads to increased sleep fragmentation and awakenings; therefore, its use should also be curtailed at least four hours before bedtime.

PRACTICAL TAKEAWAY

In addition to good sleep hygiene, consideration of diet is an important factor in ensuring good sleep. I would suggest starting by avoiding elements that impair sleep: avoid caffeine within six hours of sleep and alcohol within four hours of sleep. Then try some of the potential sleep promoting foods such as tart cherry juice, kiwifruits, fatty fish, and milk.

TRAINING: Training periodization, intensity distribution, and volume in trained cyclists

I believe that periodisation of training and intensity distribution are important considerations when preparing an athlete's training plan. There are multiple different approaches to both of these and a good coach and good athlete can use different prescriptions that are most appropriate for each athlete depending on their goals, experience, and current training needs. This study is interesting because it looks at the actual training of elite cyclists which can show how they implement these protocols.

STUDY DETAILS

1. The participants were simply described as competitive male cyclists, male well-trained cyclists, male trained cyclists, and male and female trained cyclists.
2. Five studies reported data describing block periodization (BP) models performed by well-trained, and competitive cyclists. The intervention period varied from 8 to 58 weeks in all studies.
3. Four studies reported data describing TP performed by competitive and well-trained cyclists. The intervention period varied from 8 to 12 weeks.
4. Training volume ranged from 7.5 to 10.76 hours per week in the TP and from 8.75 to 11.68 hours per week in the BP.
5. Time-intensity distribution (TID) was pyramidal in 4 studies, 2 of them implemented a BP while only one study used the TP model. Two studies described a polarized TID during BP model, while Hebisz et al described a polarized TID using a day-by-day program.
6. The main finding of the present review is that there is currently no preponderance of evidence that a specific periodization model (TP or BP), or day-by-day programming model is generally more effective in trained road cyclists.
7. On the other hand, 5 studies reported data described as BP performed by well-trained and competitive cyclists.
8. Regarding training volume, the total volume per week ranged from 7.5 to 10.76 hours per week) in the TP, and from 8.75 to 11.68 hours per week in the BP groups evaluated. It seems reasonable to assume a weekly training volume between these ranges for improving the physiological determinants of cycling performance.
9. Both polarized and pyramidal TID training have been found to be a very effective TID approaches to improve performance in endurance athletes.
10. Ultimately, we recommend that the pyramidal and polarized TID approaches be combined and adjusted based on daily monitoring, depending on the training phase or cycle, to improve endurance performance in road cyclists.

PRACTICAL TAKEAWAY

While the results of this study seem frustrating at first, that there is no evidence for an optimal training approach across a range of cyclists, it in fact suggests that there are multiple paths to achieve the same performance goals. This provides flexibility for coaches and athletes to find and use the most appropriate training plan for each athlete based on their characteristics and goals. I like the authors' recommendation of using different periodisation and time-intensity distribution approaches based on daily monitoring of the athletes and would recommend following this advice.

HYDRATION: The influence of hydration state on thermoregulation during a 161-km ultramarathon

Previous research I've shared suggested that dehydration of up to 3% did not impair performance, but that dehydration can negatively impact cognitive performance and mood. In this study the authors "sought to assess whether a loss of >2% body mass leads to elevations in core temperature during an ultramarathon".

STUDY DETAILS

1. Thirty runners agreed to take part in the study.
2. Body mass and core temperature were measured at the start, at three locations during the race and the finish.
3. Core temperature was not correlated with percent body mass change or finish time.
4. Percent body mass change was directly associated with finish time, such that the fastest runners lost the most mass.
5. It appears that a loss of >3% body mass does not contribute to rises in core temperature.
6. An emphasis on fluid replacement for body mass losses of this magnitude during prolonged exercise is not justified as a preventative measure for heat-related illnesses.

PRACTICAL TAKEAWAY

This is further evidence that dehydration of ~3% does not lead to impairments in performance. Hydration is important to allow for nutrient absorption in a race so it is still important to have a hydration plan in a race. However, athletes do not have to be concerned about dehydration if impacting performance if they don't manage to achieve their race hydration plan.

PACING: Monitoring heart rates to evaluate pacing on a 75-km MUM

Less fluctuations in pace result in faster times in a 161km ultramarathon, while uneven but conservative pacing in uphill and downhill running, and running downhills at higher relative speeds result in superior performance on trail races. In this study the authors set out to examine "pacing among twelve males on a 75-km mountain ultra marathon (MUM) and to determine whether pacing relates to final performance".

STUDY DETAILS

1. Speed and heart rates (HR) were measured continuously using a HR monitor and a global position system device.
2. An Index of Pacing (IP) was calculated by dividing the average race speed by the speed on the first race segment.
3. Performance time was correlated with IP, % of HRres, and coefficient of variation (CV) in % of HRres, but not with CV in speed.
4. On the entire race, evolution of HR was not dependent on the elevation gain.
5. Tracking HR is a safer way to rate pacing than speed tracking on a hilly course.

PRACTICAL TAKEAWAY

Pacing is important, but also challenging to achieve effectively in a hilly race. This study suggests that using heart rate as a guide can be a useful metric to control pacing. My recommendation would be to use heart rate and also to look at previous performances and splits on a race course (or if possible to run the race route) to create and execute a pacing strategy.

Thanks to Jem Arnold for sharing this additional study that provides another means of monitoring intensity: "[NIRS] may offer a more accurate alternative than HR to monitor running intensity for training and competition in hilly terrain."

NUTRITION: Dietary observations of ultra-endurance runners in preparation for and during a continuous 24-h event

I've shared studies that show athletes underfuel their training and racing (indoor cycling and Australian football). In this study the authors set out to assess "the dietary intake of amateur (males: n=11, females: n=7) ultra-endurance runners prior to, and during a 24-h ultra-endurance event".

STUDY DETAILS

1. Analysis revealed that runners did not meet the majority of CHO intake recommendations.
2. CHO intake over 24–48h pre-race was lower than recommended (4.0±1.4g·kg−1; 42±9% of total energy), although pre-race meal CHO intake was within recommended levels (1.5±0.7g·kg−1).
3. In-race CHO intake was only in the 30–60g·h−1 range (mean intake 33±12g·h−1) with suboptimal amounts of multiple transportable CHO consumed.
4. Indeed, strong to moderate positive correlations were observed between distance covered and both CHO and energy intake in each of the three diet periods studied.
5. In 24-h ultra-runners, studies examining the performance enhancing benefits of getting closer to meeting pre-race and in-race carbohydrate recommendations are required.

PRACTICAL TAKEAWAY

Fueling training and racing is important and there are many studies supporting this and providing recommendations to improve performance (search for "nutrition" on my resources page). This study shows that ultramarathon runners in 24 hours events are under-fueling and have an opportunity to improve performance through higher pre-race and in-race nutrition intakes.

An interesting case study that shows the benefits of adequate fueling is Robbie Britton's recent 24hr British record where he consumed 97g/hr.