RESEARCH: studies shared from 10 to 16 Apr 23

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

This week's quick summary:

• Rapid carbohydrate loading
• Shoe stiffness and cost of running on steep gradients
• Elite vs experienced trail runners
• Moderate exercise and the pharmacokinetics of caffeine
• Caffeine taken immediately prior to the start of exercise

NUTRITION: Rapid carbohydrate loading after a short bout of near maximal-intensity exercise

Previous research that I've shared showed that the capacity for glycogen storage is greater than generally believed and that a high-carbohydrate meal prior to an event increased time to exhaustion. With this in mind, it's interesting to consider this study in which the authors set out "to examine whether a combination of a short bout of high-intensity exercise with 1d of a high-carbohydrate intake offers the basis for an improved carbohydrate-loading regimen".

STUDY DETAILS

1. Seven endurance-trained athletes cycled for 150s at 130% VO2peak followed by 30s of all-out cycling.
2. During the following 24h, each subject was asked to ingest 12g.kg-1 of lean body mass (the equivalent of 10.3g.kg-1 body mass) of high-carbohydrate foods with a high glycemic index.
3. Muscle glycogen increased from preloading levels of 109.1 to 198.2mmol.kg-1 wet weight within only 24h, these levels being comparable to or higher than those reported by others over a 2- to 6-d regimen.
4. Densitometric analysis of muscle sections stained with periodic acid-Schiff not only corroborated these findings but also indicated that after 24h of high-carbohydrate intake, glycogen stores reached similar levels in Type I, IIa, and IIb muscle fibers.
5. This study shows that a combination of a short-term bout of high-intensity exercise followed by a high-carbohydrate intake enables athletes to attain supranormal muscle glycogen levels within only 24h.

PRACTICAL TAKEAWAY

In the past, carbohydrate loading protocols of anywhere from 2-6 days were recommended. This study shows that a single day of loading may be sufficient which makes it both easier to achieve and to fit into a pre-race plan. It is important to note that the quantities of carbohydrate consumed are quite large and that athletes should probably weigh their food (at least the first time following this protocol) to ensure they eat enough. My recommendation would be to aim to eat 10-12g/kg body weight over three to four meals on the day before the race.

EQUIPMENT: Increasing shoe longitudinal bending stiffness is not beneficial to reduce energy cost during graded running

Research into supershoes has shown that they can be beneficial for level running (and small gradients up to 3%) and for slower runners. In this study, the authors set out to "to identify the effect of longitudinal bending stiffness (LBS) on cost of running (Cr) during uphill (UH) running" at much higher gradients (15%).

STUDY DETAILS

1. Twenty well-trained male runners participated in this study.
2. Cr was determined using gas exchange during nine 4-minute bouts performed using 3 different LBS shoe conditions at 2.22 and 4.44 m/s on level and 2.22 m/s UH (gradient: + 15%) running.
3. There was no significant effect of LBS and no significant LBS × grade interaction.
4. Results were characterized by a very large inter-individual variability in response to LBS changes.
5. The very large inter-individual differences in response to changes in LBS suggest that increasing shoe LBS may be beneficial for some runners.

PRACTICAL TAKEAWAY

The benefit of carbon-plated shoes for steep uphills is not as clear as it is for level running. The gradient used in this study is most likely to occur in trail races and therefore the benefit of carbon-plated shoes for trail runners is not as straight-forward as it is for road runners (who should definitely use supershoes if they're looking for the best performance). The large variability suggests that there could be some benefit for certain athletes so my recommendation would be to test different shoes to find the most comfortable and fastest for each athlete. For trail runners, this may or may not be a carbon-plated shoe.

PHYSIOLOGY: Elite vs. Experienced Male and Female Trail Runners

Trail running performance is determined by similar physiological traits to other endurance sports. In short trail races, combined VO2max and fat mass model explained 83.9% of the total variance. In longer races, differences in performance were uniquely significant for the second ventilatory threshold. This study investigates further with the aim "to compare cost of running (Cr) and biomechanical and neuromuscular characteristics of elite trail runners with their lower level counterparts".

STUDY DETAILS

1. Twenty elite (10 females; ELITE) and 21 experienced (10 females; EXP) trail runners participated in the study.
2. Cr and running biomechanics were measured at 10 and 14 km·h−1 on flat and at 10 km·h−1 with 10% uphill incline.
3. Athletes also reported their training volume during the previous year.
4. Despite no differences in biomechanics, ELITE had a lower Cr than EXP.
5. Despite nonsignificant difference in maximal lower-limb power between groups, ELITE displayed a greater relative torque and lower maximal velocity in the power-torque-velocity profile (PTVP).
6. Females displayed shorter contact times compared with males, but no sex differences were observed in Cr.
7. Strength training can be suggested to lower level trail runners to improve Cr and thus TR performance.

PRACTICAL TAKEAWAY

The difference in performance between experienced and elite athletes was primarily due to running economy. There are multiple ways to try and improve running economy which should be the aim of athletes hoping to improve their trail performance. These include increasing total running volume, running short running economy intervals, and strength training. While the training volume may be naturally addressed in a training plan that challenges an athlete, I would recommend ensuring that the other two elements of strength training and short intervals are deliberately considered each season.

CAFFEINE: Effects of moderate exercise on the pharmacokinetics of caffeine

I found this study when researching the half-life of caffeine to try and determine the doses needed during longer endurance events. The pre-event dose is clear from the literature (see the study below), but how much caffeine to take during a longer event is not as evident from the research I've seen. Therefore, understanding the "effect of moderate exercise on the kinetics of caffeine in 12 healthy volunteers-6 heavy coffee drinkers (HD) and 6 light coffee drinkers (LD)" is particularly useful.

STUDY DETAILS

1. Kinetics at Rest was measured first (R): the subjects remained at rest for 8h after a single 250mg dose of caffeine.
2. One week later, the Exercise Kinetics (E) was measured under the same conditions, but with the subjects performing moderate exercise (30% of VO2 max) during the first hour of the study.
3. Exercise raised the maximal plasma caffeine concentrations and reduced both the half-life (R 3.99h: E 2.29h) and the volume of distribution.
4. Both during exercise and at rest, HD had a greater half-life elimination and volume of distribution than LD.

PRACTICAL TAKEAWAY

Exercise does appear to shorten the half-life of caffeine. However, the half-life is still a significant amount of time (~2.5hrs) so a boosting dose of caffeine is probably only needed every two hours. I would suggest that the protocol I use and recommend fits well with this research. My recommendation is to take 3-6mg/kg body weight 60' before a race and then to supplement with an additional 100mg every two hours (i.e. at 1hr, 3hrs, 5hrs, etc into the race).

CAFFEINE: Caffeine ingestion during exercise to exhaustion in elite distance runners

There is a clear benefit for the use of caffeine for endurance performance. A good starting point to read about this is the international society of sports nutrition position stand: caffeine and exercise performance. However, many endurance athletes do not follow the recommendations of taking 3-6mg/kg body weight 60' before exercise. This paper is therefore very interesting as as it set out "to determine whether a large dose of caffeine (10 mg.kg-1) taken immediately prior to the start of endurance exercise would have the desired effect of increasing endurance performance"

STUDY DETAILS

1. Six males, who were not habitual caffeine users and who had performed at least two marathons, served as subjects in this experiment.
2. They ran on a treadmill at a speed which had been calculated would elicit 75% of their VO2max for 45 minutes, after which time the speed was increased by two miles per hour till exhaustion.
3. During the caffeine trial the athletes ran further than either the control or placebo conditions.
4. Blood triglycerides after the start of the test were always higher in the caffeine condition but this was only significant at the 45 minute and end of exercise collection periods.
5. The results suggest that endurance athletes can use caffeine just prior to exercise rather than one to three hours prior to exercise.

PRACTICAL TAKEAWAY

A caffeine dose taken immediately before the start of exercise appears to provide all the benefits of a more standard protocol of taking it 60' before exercise. However, it is worth nothing that this was a very large dose of caffeine that can probably only be achieved by taking caffeine pills. I would recommend following a more traditional approach of taking 3-6mg/kg an hour before a race and keeping this option as a back-up in case something happens and a last-minute dose is required.