RESEARCH: Studies from 5 to 11 Feb 24
Sharing research and insights from coaches, scientists and athletes to help us improve endurance performance.
This week’s quick summary:
Ice slurry ingestion and half-marathon performance
Strategic self-talk and running performance
Glucose oxidation rates are impacted by starting glycogen status
Effects of ibuprofen during 42km trail running
Effects of time-restricted eating on aerobic capacity
HEAT: Ad libitum ice slurry ingestion and half-marathon performance in a hot environment
I have shared a number of studies on preparing for the heat (see the HEAT archives) with results showing that a combination of ice ingestion and head cooling and also neck cooling could be beneficial. In this study, the authors set out “to investigate the impact of ad libitum ice slurry ingestion on physiological variables and half-marathon performance in hot conditions compared to water at 37°C”.
STUDY DETAILS
Participants ran two half marathons while freely consuming either ice slurry (-1°C) or water (37°C).
Athletes ingested 45% less ice slurry than water during ad libitum trials.
80% of athletes reported gastric discomfort and headaches with ice slurry ingestion.
Physical performance, heart rate, and thermal perception were unaffected by beverage temperature or amount.
Lower beverage ingestion correlated with a 3-4% improvement in half-marathon performance.
PRACTICAL TAKEAWAY
The results of this study surprised me as I suspected that ingesting an ice slurry would help with cooling and performance. However, in this study that didn’t appear to be the case and it appeared that even drinking less and ingesting less ice slurry than recommended was beneficial for performance. I still believe that there is some benefit to using ice in hot conditions if it provides a perceptual benefit, however, I recommend testing out different strategies to see if they work and if the effort is worth the benefit before implementing these sorts of interventions into races.
PSYCHOLOGY: Strategic self-talk and running performance in a middle-distance race
Self-talk during endurance sports can help to improve performance (I have some specific studies to share on this topic in coming months). Most of the research that I have seen on this in the past was based on tests in the laboratory. In this study, the author set out “to bridge the gap between lab-based findings and real-world application in sport performance”.
STUDY DETAILS
22 runners (12 males, 10 females; mean age: 31.4 years) participated.
Participants underwent a 5-week self-talk intervention.
Performance was assessed via two time-trials, five weeks apart.
Both intervention and control groups showed improved performance.
The self-talk group demonstrated significantly better times in the final trial.
PRACTICAL TAKEAWAY
This study showed that implementing a structured self-talk intervention over five weeks can notably enhance running performance. My recommendation for athletes is to try self-talk in their training and to develop cues that they can use when racing. The best self-talk appears to be positive, in the third-person, and instructional rather than motivational. In this study the intervention group spent a few weeks trying different self-talk and refining the cues to the ones they found worked best for them. I recommend that anyone who wants to try this should follow a similar procedure noting which self-talk and cues they want to use in races.
NUTRITION: Reduced oxidation rates of ingested glucose during prolonged exercise with low endogenous CHO availability
I have shared many studies about moderating and controlling carbohydrate ingestion before and during training (see the Nutrition - CHO studies section). This study adds some more insight into the impact of starting glycogen stores on glucose oxidation rates during exercise. In this study, the authors set out “to explore the impact of endogenous carbohydrate (CHO) availability on glucose oxidation rates during moderate-intensity exercise”.
STUDY DETAILS
Seven well-trained cyclists completed two 120-minute cycling trials at 57% maximal O2 consumption.
Pre-exercise glycogen concentrations were manipulated: one trial with low glycogen (LG) and another with moderate-to-high glycogen (HG).
Ingestion of corn-derived glucose solution at the start (4ml/kg) followed by 2 ml/kg every 15 minutes.
Total CHO oxidation was lower in LG than HG during 60-120 minutes (84 +/- 7 vs. 116 +/- 8g).
Maximal exogenous oxidation rates were lower in LG (0.64 +/- 0.05g/min) than HG (0.88 +/- 0.04g/min).
PRACTICAL TAKEAWAY
This study suggests that manipulating glycogen levels through exercise and carbohydrate intake before exercise can influence glucose oxidation rates during moderate-intensity exercise. Athletes who start with lower glycogen stores appear to have lower glucose oxidation rates during exercise. I have two recommendations based on this study: 1) make sure to start important sessions where athletes are practicing race nutrition with full glycogen stores; 2) if athletes are performing low-CHO training sessions, then the in-training nutrition also needs to be moderated to lower intakes than normal.
SUPPLEMENTATION: Effects of ibuprofen during 42km trail running on oxidative stress, muscle fatigue, muscle damage and performance
This study’s introduction notes that “up to 75% of marathon runners ingest non-steroidal anti-inflammatory drugs (NSAIDs) during competition”. The authors wanted “to understand how NSAIDs affect endurance athletes during competition” for trail runners.
STUDY DETAILS
Twelve male trail runners were randomly assigned to either a placebo group or an ibuprofen group.
The IBU group took a 400mg capsule 15 minutes before the race and another after 5 hours, while the placebo group received no medication.
In intergroup analysis, the placebo group showed a significant 70.1% increase in thiobarbituric acid reactive substances (TBARS), indicating higher oxidative stress.
The IBU group exhibited a 31.46% increase in sulphhydryl groups (SH), suggesting reduced oxidative stress.
While the IBU group experienced a 55% improvement in squat jump (SJ), there was no significant effect on creatine kinase levels, pace, speed, or finish time.
PRACTICAL TAKEAWAY
In this study, the results showed that ibuprofen did not enhance physical performance or prevent muscle damage in trail runners. There are also significant potential downsides to taking NSAIDs during exercise, in particular risk of kidney damage. My recommendation is simple: don’t take ibuprofen during exercise.
PHYSIOLOGY: Effects of time-restricted eating on aerobic capacity, body composition, and markers of metabolic health in healthy male recreational runners
I have shared one study before on time-restricted eating (TRE) which showed that incorporating eight weeks of 16:8 TRE may aid in weight management through a reduction in body mass, attributed to a decrease in daily energy intake. In this study, the authors set out “to explore the impact of time-restricted eating (TRE) on aerobic capacity, body composition, and metabolic health in young male recreational runners”.
STUDY DETAILS
Sixteen male recreational runners participated in a randomized-crossover trial.
Participants followed either a 4-week TRE regimen or their habitual diet, with assessments conducted before and after each intervention.
TRE involved an 8-hour eating window, while non-TRE participants followed their regular dietary patterns.
No significant differences were observed in body composition or metabolic health markers between the two conditions.
Both groups showed improvements in aerobic capacity, including first ventilatory threshold, maximum oxygen uptake (VO2max), and velocity at VO2max.
PRACTICAL TAKEAWAY
In this study, time-restricted eating did not yield significant changes in body composition or metabolic health markers, and it also did not provide additional benefits for aerobic capacity compared to a habitual diet in young male recreational runners. My recommendation is that TRE is an intervention that needs to be used very cautiously and only for athletes who are intentionally looking to lose weight. It should probably be a last resort for athletes who are not able to achieve their race weight following their normal diet and training routine.
Quick summary from last week’s paid newsletter
Paid subscribers receive a newsletter every week and have full access to all newsletters listed in the archives (over 300 studies and practical takeaways). Last week, the newsletter covered studies on the following topics:
Impact of reduced pre-exercise glycogen on performance and adaptation
Effect of different strength training protocols on running economy
The use of hyperoxia in sports training
Ketone ingestion with and without CHO and its impact on running economy
Endurance athletes’ compliance with nutrition best practices