RESEARCH: Studies from 9 to 15 Jun 25
Sharing research and insights from coaches, scientists and athletes to help us improve endurance performance.
This week’s quick summary:
Effects of 6-week sprint interval training on running performance
Accuracy of self-reported foot strike pattern among endurance runners
Exploring the use of digital technology for injury prevention
Short-term supplemental breathwork and performance of recreational runners
Effects of a single dose of a betalain-rich concentrate on running performance
TRAINING: Effects of 6-week sprint interval training compared to traditional training on the running performance of distance runners
Previous research has shown that sprint interval training (SIT) can improve endurance performance, but few studies have examined its effect in already well-trained runners. In this study, the authors aimed to "compare the effects of sprint interval training versus traditional training on running performance in well-trained male distance runners".
STUDY DETAILS
20 well-trained male distance runners (VO2 Max: 67.4±4.5mL/kg/min; 5000m PB: 14'38″47±00'23″46) were randomly assigned to either a sprint interval training group or a traditional training group.
Both groups trained twice weekly for 6 weeks, continuing their usual training otherwise.
Performance tests included VO2 Max, oxygen cost, time to exhaustion (TTE), and running times for 100m, 400m, and 3000m.
The sprint interval group improved significantly in TTE and 100m, 400m, and 3000m performance.
The traditional training group improved only in 400m, while the sprint interval group had superior gains in 3000m performance and greater effect sizes in physiological metrics.
PRACTICAL TAKEAWAY
This study showed that adding sprint interval sessions twice a week over six weeks can enhance time to exhaustion and short-to-mid-distance running performance in well-trained distance runners. My recommendation for athletes is to include sprint interval training for 6 weeks as the first phase in their training plan after returning from an off-season or a race. The protocol used in this study was 2 sessions per week of 10 x 30” sprint with 3.5’ recovery.
RELATED RESEARCH
PHYSIOLOGY: Accuracy of self-reported foot strike pattern detection among endurance runners
Foot strike pattern is commonly linked to running-related injuries (RRI) and is often a focus in athlete rehabilitation and performance training. Previous research suggests that runners must first be aware of their strike pattern to successfully modify it, and misperception may hinder gait retraining and shoe transitions. In this study, the authors set out to “determine the accuracy of self-reported foot strike pattern among endurance runners to identify what factors were predictive of accurate foot strike detection and recent RRI”.
STUDY DETAILS
710 endurance runners (51.5% female, average age 35.4 years) participated; about half were training competitively.
Participants self-reported foot strike pattern (rearfoot, non-rearfoot, or unknown) and completed a treadmill run at self-selected speed while their actual strike was verified using 3D motion capture and video.
Only 42.7% accurately identified their foot strike; non-rearfoot runners were more accurate (69.5%) than rearfoot runners (34%).
The highest injury prevalence (73%) was seen in runners who did not know their strike pattern.
Footwear heel-to-toe drop and recent shoe changes were significant predictors of both strike detection accuracy and recent injury.
PRACTICAL TAKEAWAY
This study showed that many endurance runners misidentify their own foot strike pattern, particularly rearfoot strikers. Runners unaware of their strike had higher injury rates, and shoe characteristics—especially heel-to-toe drop and recent changes—were linked to both injury and misidentification. My recommendation for athletes who are struggling with injuries is to film their running. This can help to identify foot strike pattern and any other issues that may be present in their stride. Sometimes this can lead to better shoe choices and it can also be useful information to share with a physio.
RELATED RESEARCH
EQUIPMENT: Exploring the use of digital technology for injury prevention and self-management among recreational runners
Recreational runners increasingly rely on digital tools like running watches and smartphone apps to track training. While these technologies are widely adopted, their use for injury prevention and self-management remains limited. In this study, the authors aimed "to “explore digital technology use among recreational runners and assess attitudes toward a proposed digital intervention for running-related injury (RRI) prevention and self-management”.
STUDY DETAILS
The study surveyed 232 recreational runners in Wales using an online questionnaire distributed over 7 weeks.
97% of participants used digital technology for training, mainly running watches (45.1%) and smartphone apps (37.6%).
Younger (18–24 years) and less experienced runners (3 months–2 years) were more likely to use multiple apps.
Most runners did not find their current technologies helpful for injury prevention or management.
84.5% expressed strong interest in a trustworthy, evidence-based intervention with injury advice, strength exercises, and diagnostic tools.
PRACTICAL TAKEAWAY
This study showed that although recreational runners frequently use digital tools to monitor training, these tools are not perceived as helpful for preventing or managing injuries. My recommendation for athletes is to think carefully about what data they track to ensure that it is useful and actionable and not just a distraction. Understanding a simple set of metrics - for example weekly distance, time, and vertical gain - can provide insight that support subjective measures and sensations. Many training load metrics and recovery scores appear useful, but do not reflect the reality of the training state of the athlete.
RELATED RESEARCH
BREATHING: The effects of a short-term supplemental breathwork protocol on the aerobic performance of recreational runners
Recent research has highlighted the potential of breathing interventions, such as nasal or functional breathing, to support endurance performance by influencing respiratory efficiency, oxygen utilisation, and carbon dioxide tolerance. In this study, the authors aimed to “determine whether a four-week functional breathing protocol improves VO2 Max, time to exhaustion, and breath-hold time in recreational runners”.
STUDY DETAILS
16 recreational runners were randomly assigned to either a functional breathing protocol group (FBP, n=8) or a control group (CON, n=8).
Over four weeks, both groups followed an aerobic endurance training plan, but only the FBP group performed daily breathwork exercises and nasal-only breathing during low-intensity sessions.
Outcomes measured before and after included resting breath-hold time, time to exhaustion and VO2 Max during nasal-only breathing, and VO2 Max with unrestricted breathing.
The FBP group improved their breath-hold time significantly more (+11.7s) than the CON group (+1.9s).
No significant differences were found between groups for time to exhaustion or VO2 Max under either breathing condition, though both groups had a small (~3.0%) increase in VO2 Max over time.
PRACTICAL TAKEAWAY
This study showed that adding daily breathwork and nasal-only breathing to endurance training did not lead to meaningful improvements in VO2 Max or running performance beyond what standard training alone achieved. My recommendation to athletes is to follow their natural breathing patterns during running and not to force any specific breathing pattern or protocol.
RELATED RESEARCH
SUPPLEMENT: Effects of a single dose of a betalain-rich concentrate on determinants of running performance and recovery muscle blood flow
Previous research has suggested that betalains—phytonutrients found in beets and other plants—may offer antioxidant and anti-inflammatory benefits that could influence exercise performance and recovery. While some studies have shown promise in multi-dose supplementation protocols, the acute effects of a single dose remain unclear. In this study, the authors aimed to “examine the effects of a single dose of a betalain-rich concentrate (BRC) on determinants of running performance and recovery lactate clearance”.
STUDY DETAILS
17 male recreational runners (mean age 19.0 years; VO2 Max: 58.9ml/kg/min) participated in a randomised, triple-blind, placebo-controlled, crossover trial.
Participants consumed 100mg of either BRC or a placebo and completed running at 60% and 80% of VO2 Max, followed by a VO2 Max test.
Muscle oxygenation during and after exercise was measured using near-infrared spectroscopy; recovery blood lactate was also analysed.
Compared to placebo, BRC resulted in lower heart rate at 80% VO2 Max and at HRmax, and a lower rating of perceived exertion at 60% VO2 Max.
BRC improved post-exercise muscle oxygenation at 3–5 minutes but had no effect on running economy, VO2 Max, or lactate clearance.
PRACTICAL TAKEAWAY
This study showed that a single dose of betalain-rich concentrate may modestly reduce heart rate and perceived exertion during submaximal running, and improve early post-exercise muscle oxygenation. While it did not enhance VO2 Max or lactate clearance, it may support cardiovascular efficiency and recovery. My recommendation for athletes is to test beetroot and related betalain-rich products to see if they provide any benefit for them. The research is not clear on the benefit of these products yet, so each individual needs to test them and see if they can feel any benefit before using them prior to races.
RELATED RESEARCH
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 (655 studies and practical takeaways). Last week, the newsletter covered studies on the following topics:
Protein nutrition for endurance athletes
Do compression garments enhance running performance?
Effect of strength training methods on runners’ athletic performance
Differences in cardiac adaptation among male and female marathon runners
Nutritional intake and timing of marathon runners
