RESEARCH: Studies from 30 Sep to 6 Oct 24
Sharing research and insights from coaches, scientists and athletes to help us improve endurance performance.
This week’s quick summary:
Effect of sodium bicarbonate on prolonged running performance
Isometric calf-strength training to improve running economy
Deviation of individual response for VO2 Max following intervention
Effects of non-nutritive sweeteners on body weight and BMI
HR does not reflect the %VO2 Max during the marathon
SUPPLEMENT: Effect of sodium bicarbonate on prolonged running performance
Sodium bicarbonate has traditionally been used for athletes in shorter events. However, athletes in longer races such as cycling stage races, marathons, and ultra-marathons have been using it before and sometimes even during races. In this study, the authors set out to “assess the ergogenic effects of an oral sodium bicarbonate (BICA) substitution upon exhaustive intensive endurance running performance”.
STUDY DETAILS
18 trained runners (VO2 Max 61.2 ± 6.4 ml/min/kg) participated in a double-blind, randomised cross-over study.
Participants ingested either BICA (0.3g/kg) or a placebo (4g NaCl) before completing two graded exercise tests and two constant-load tests until exhaustion.
Time to exhaustion did not differ significantly between BICA (39.6min) and placebo (39.3min).
Maximum running speed (Vmax) increased with BICA (17.4km/h vs. 17.1km/h placebo), though VO2peak differences were not statistically significant.
BICA caused significant increases in maximum blood lactate and maintained normal pH post-exercise but led to gastrointestinal side effects in 15 participants.
PRACTICAL TAKEAWAY
The results of this study suggest that for endurance runners, BICA supplementation may improve maximum running speed but does not significantly affect endurance performance or time to exhaustion. Additionally, while it buffers pH levels during exercise, the gastrointestinal side effects could outweigh its marginal benefits. My recommendation for athletes in longer events is to be cautious with bicarbonate. If they want to try it, make sure to test it in training to determine if they have any GI issues and whether or not it is beneficial for them.
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STRENGTH: Exercise-induced changes in triceps surae tendon stiffness and muscle strength affect running economy in humans
Strength training has benefits for running economy. Most research shows that heavy lifting and weights provide the best benefit, however, in this study the authors looked at isometric strength exercises. They set out “to understand how tendon stiffness and muscle strength impact oxygen consumption and running efficiency”.
STUDY DETAILS
The study included 26 participants: 13 in the exercise group (EG) and 13 in the control group (CG).
The EG completed a 14-week resistance training programme, while the CG maintained their usual training.
Researchers measured maximum isometric voluntary contractile strength, TS tendon-aponeurosis stiffness, running kinematics, and gastrocnemius medialis fascicle length.
The EG saw a 7% increase in muscle strength and a 16% increase in tendon stiffness, leading to a 4% reduction in oxygen consumption during running at 3.0 and 3.5ms−1.
No changes in running kinematics, fascicle length, or series-elastic element (SEE) elongation were found in either group.
PRACTICAL TAKEAWAY
The results of this study suggest that resistance training that increases tendon stiffness and muscle strength in the triceps surae (calf muscles) can improve running economy by reducing oxygen consumption. My recommendation is to try the protocol used in this study (4 sessions a week of 5 sets of 4 repetitions of 3” isometric load / 3” recovery) as it requires minimal time and could provide very a large benefit in running economy.
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PHYSIOLOGY: Standard deviation of individual response for VO2 Max following exercise intervention
VO2 Max is often used as an outcome measure to test the effectiveness of an intervention is sports science research. Many athletes and coaches also use it as a means to check progress and evaluate an athlete. In this review, the authors set out “to evaluate inter-individual differences in VO2 Max trainability across aerobic exercise training protocols”.
REVIEW DETAILS
A total of 24 studies were included from an initial search of 32,968 articles.
Participants were from studies that used standardised, supervised aerobic exercise protocols.
Exercise interventions were compared against non-exercising control groups, with VO2 Max measured pre- and post-intervention.
Researchers calculated the standard deviation of individual response (SDIR) to assess variation in VO2 Max changes.
Findings showed most of the observed differences were due to measurement error, and there was no strong evidence for inter-individual differences in trainability.
PRACTICAL TAKEAWAY
The results of this review suggest that personal variability in response to aerobic exercise may not be as significant as previously thought. In addition, VO2 Max measurements may not be the most valuable way to measure any improvement in fitness. The outcome suggests that most people will see relatively consistent results from structured training programmes. My recommendation for athletes is to follow the best-practice for training (plans and protocols that have been effective for many athletes) and to measure their progress through races or field tests.
RELATED RESEARCH
Eager to set a record in a vertical race? Test your VO2 Max first!
VO2 Max and velocity at VO2 Max play a role in ultradistance trail-running performance
SUPPLEMENT: Effects of non-nutritive sweeteners on body weight and BMI in diverse clinical contexts
One of the options people can use when trying to lose weight is to switch to the “diet” version of drinks or foods. These typically contain a non-nutritive sweetener to provide sweetness without the sugar content. In this review, the authors set out “to assess whether non-nutritive sweeteners (NNS) can aid in weight management, particularly in individuals with overweight or obesity”.
REVIEW DETAILS
The review included 20 studies with 2914 participants, both healthy-weight and overweight/obese, across various age groups.
The intervention was the use of NNS for a minimum of 4 weeks, with comparisons to caloric and noncaloric alternatives, including water, placebo, and sucrose.
Weight and BMI differences were measured as the primary outcomes of interest.
Significant weight/BMI reductions were observed in participants consuming NNS compared to those using sucrose, particularly in unrestricted energy diets.
No significant effects were found when NNS were compared to water, placebo, or when used in weight-reduction diets.
PRACTICAL TAKEAWAY
The results of the review suggest that replacing sugar with NNS could help reduce weight, especially for individuals with overweight/obesity who are not following strict calorie-restricted diets. My recommendation for athletes trying to lose weight is to follow a diet plan and carefully manage their calories ingested and used. One of the methods that can help to reduce calories ingested while maintaining a similar taste or keeping a certain “treat” in a diet is to use artificially sweetened options. This should be a small part of controlling calories ingested, but can be a useful psychological option to maintain consistency and to control cravings.
PACING: Heart rate does not reflect the %VO2 Max in recreational runners during the marathon
Managing pacing in a marathon is a difficult challenge as it requires balancing a desired outcome which is pace-based with physiology which is based on an athlete’s ability. Using heart rate could be one way to control pacing and ensure an optimal outcome in a marathon. In this study, the authors set out “to evaluate whether heart rate is a reliable indicator of oxygen uptake during a marathon”.
STUDY DETAILS
10 male endurance runners participated, each with a marathon finish time goal.
The participants performed a pre-test to determine VO2 Max, HR Max, and anaerobic threshold using a road-based incremental test.
Two weeks later, they ran a marathon while wearing a portable gas exchange system to measure continuous HR and oxygen uptake.
The %HR Max remained stable after the 5th km, staying between 88%-91%.
The %VO2 Max significantly decreased from 81% at 5km to 74% at 42km, while the ratio of %HR Max to %VO2max increased between the 5th and 42nd km.
PRACTICAL TAKEAWAY
The authors of this study suggest that heart rate alone is not a reliable tool for pacing during a marathon. Their recommendation is that runners should focus on perceived effort and training with a rating of perceived exertion (RPE) scale to better align effort with oxygen demands over the course of the race. I agree with this recommendation and would add that learning more about pacing through race-pace training sessions is the optimal way to identify which metrics to follow and how to assess whether or not a pace is ideal for an athlete in a marathon.
When I shared this study on X, there was plenty of input from athletes and coaches. One important note was that 88-91% of HR Max is probably too high a target for a marathon which may have led to poor pacing. Another note I appreciated from Derek Griffin was that “the best marathoners intuitively run off perception of effort”.
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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 (455 studies and practical takeaways). Last week, the newsletter covered studies on the following topics:
Milk protein addition to a CHO-electrolyte rehydration solution
Muscle activity and fascicle behavior during running in supershoes
Physiological and performance outcomes following a 3-week altitude camp
Role of kicking action in front crawl
Hypohydration influences key renal functions during stress