RESEARCH: Studies from 6 to 12 Jan 25
Sharing research and insights from coaches, scientists and athletes to help us improve endurance performance.
This week’s quick summary:
Delaying post-exercise carbohydrate impairs next-day exercise capacity
Self-paced field running test in monitoring fatigue and training adaptations
Performance-enhancing drugs in healthy athletes
The impact of stretching on running performance and running economy
Disparate mechanisms of fatigability in running versus cycling
NUTRITION: Delaying post-exercise carbohydrate intake impairs next-day exercise capacity but not muscle glycogen or molecular responses
Previous research has shown that post-exercise carbohydrate intake timing can affect muscle glycogen resynthesis and subsequent exercise performance. In this study, the authors aimed “to investigate the impact of delayed carbohydrate intake on muscle glycogen, molecular responses, and subsequent high-intensity interval exercise (HIIE) capacity".
STUDY DETAILS
9 recreationally active men performed HIIE cycling sessions on two occasions, with either immediate or delayed carbohydrate intake post-exercise.
Participants consumed either carbohydrates (2.4g/kg) or water during 0-3 hours post-HIIE, with total carbohydrate intake matched over 24 hours.
Skeletal muscle samples were analysed for glycogen, mRNA content, and signalling proteins at various time points up to 24 hours post-exercise.
After 24 hours, participants repeated the HIIE protocol to failure, with blood lactate, heart rate, and perceived effort measured.
Delayed carbohydrate intake reduced next-day HIIE capacity by 5 intervals and increased perceived effort, despite similar muscle glycogen levels and molecular responses between conditions.
PRACTICAL TAKEAWAY
The results of this study showed decreased performance in training the next day after limiting post-training carbohydrate consumption. It’s interesting that this decrease in performance occurred even though the participants’ muscle glycogen levels were the same as before the first day. My recommendation for athletes who are training consistently with high training loads each day is to ensure that they are eating enough carbohydrates after their sessions (this study used 2.4g/kg). There may even be a benefit from fueling all training sessions, even easy ones, to help maintain the quality of training each day.
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FATIGUE: Self-paced field running test in monitoring fatigue and training adaptations in recreational runners
Field-based running tests are more accessible and are typically easier to repeat than laboratory testing throughout a season for most athletes. In this study, the authors set out “to evaluate the reproducibility and sensitivity of a self-paced field running test (SFT) for monitoring changes in endurance performance”.
STUDY DETAILS
27 recreational runners (11 women) participated in a 6-week training intervention comprising a 3-week baseline, 2-week overload, and 1-week recovery period.
Participants performed an incremental treadmill test before baseline, 3000m running tests at four time points, and weekly SFTs consisting of submaximal and maximal sections.
SFT speeds showed significant correlations (r = .68–.93) with peak and lactate threshold speeds from the incremental treadmill test.
Intraclass correlations for SFT parameters ranged from .77 to .96, with the highest for average speed of 6 × 3-minute intervals.
Repeated-measures correlations between 3000m speeds and corresponding SFT speeds were significant but low (r = .24–.29) for submaximal and maximal sections.
PRACTICAL TAKEAWAY
The results of this study suggest that field tests appear to be a reproducible method for estimating endurance performance. My recommendation for athletes and coaches is to include field tests every 4 to 6 weeks to help track progress and assess how athletes are responding to their training plans. Ideally, these tests will be in similar conditions and within the same place each time they are performed. I like to use a 4km time trial on the track the day after a rest day as an easily repeatable test.
RELATED RESEARCH
SUPPLEMENTS: Performance-enhancing drugs in healthy athletes: An umbrella review of systematic reviews and meta-analyses
Anyone who follows sports knows of cases of athletes using performance-enhancing drugs. However, we often wonder how much those drugs actually improve performance. The authors explained that the purpose of this review “was to compile data reported in high-quality systematic reviews (SRs) and meta-analyses (MAs) on common PEDs used by athletes to provide an evidence-based overview of the reported changes in biological and sport-dependent parameters that affect athletic performance".
REVIEW DETAILS
The study included 27 papers evaluating five pharmacological interventions: androgenic anabolic steroids (AAS), growth hormone (GH), creatine, recombinant human erythropoietin (rHuEPO), and cannabis.
AAS led to a 5% to 52% increase in strength and a 0.62 standard mean difference in lean body mass, but also caused lipid derangements.
GH altered body composition without providing strength or performance benefits and carried risks such as soft tissue oedema, fatigue, arthralgias, and carpal tunnel syndrome.
Creatine use during resistance training safely increased total and lean body mass, strength, and performance in high-intensity, short-duration, repetitive tasks.
rHuEPO showed limited evidence of performance benefits despite increases in VO2 Max and maximal power output, and was associated with severe cardiovascular risks.
PRACTICAL TAKEAWAY
This study showed that there are significant benefits to using performance-enhancing drugs (up to 52% increase in strength from using anabolic steroids!). However, the authors also shared the significant health consequences these drugs can have and the issues in the list above are very serious. Interestingly, they also included creatine in the review (it’s not a banned substance) and reported both performance benefits and a lack of side effects. My recommendation is to avoid illegal performance-enhancing drugs as they are unethical and can have serious health consequences.
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PHYSIOLOGY: The impact of a single stretching session on running performance and running economy
Most athletes stretch before practice or training, however its impact on running economy (RE) and performance remains ambiguous. In this scoping review, the authors set out “to investigate the effects of a single bout of stretching on RE and running performance”.
REVIEW DETAILS
The review included 11 studies with 111 healthy adult participants, assessing acute effects of stretching on 44 parameters (14 performance-related and 30 metabolic).
Static stretching up to 90 seconds per muscle group showed minor improvements in RE (1%) but negatively affected running performance (-1.4%).
Dynamic stretching resulted in negligible changes in RE (-0.79%) but significantly improved running performance (9.8%) when performed for ≤220 seconds overall.
Stretching effects varied by technique and duration, with shorter static stretches (<60 seconds) being less detrimental.
Less flexible runners benefited more from stretching, suggesting that optimising flexibility enhances RE.
PRACTICAL TAKEAWAY
This review showed that static stretching before running could negatively impact performance. My recommendation is to use dynamic stretching for short durations (≤220”) before running, and to use static stretching for after training or as part of a mobility routine. Any static stretches should be brief (<60” per muscle group) to avoid adverse effects on running performance.
RELATED RESEARCH
FATIGUE: Disparate mechanisms of fatigability in response to prolonged running versus cycling of matched intensity and duration
Running and cycling often feel different in how demanding they are and, in practice, cyclists are able to do far greater training volume than runners. In this study, the authors aimed to “examine the differences in neuromuscular function alterations induced by matched-intensity and duration cycling and running exercise".
STUDY DETAILS
17 endurance-trained male participants performed 3-hour cycling and running sessions at 105% of gas exchange threshold.
Neuromuscular assessments included maximal voluntary contractions, voluntary activation, high- and low-frequency doublets, potentiated twitches, and motor evoked potentials.
Both running and cycling reduced maximal voluntary contraction by approximately 25%.
Running caused greater reductions in voluntary activation and thoracic motor evoked potentials compared to cycling.
Cycling led to greater reductions in high-frequency doublets and low- to high-frequency doublet ratios compared to running.
PRACTICAL TAKEAWAY
This study showed that running may cause more significant impairments in nervous system function, especially at the spinal level, while cycling may lead to greater contractile function impairments. My recommendation for runners is to focus on performing their key sessions (speed sessions, long runs, race simulations) as runs, then consider how the rest of their training volume can be done in a less demanding way. This might be running on a treadmill or on trails, or shifting some volume to other sports such as cycling or cross-country skiing.
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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 (545 studies and practical takeaways). Last week, the newsletter covered studies on the following topics:
The pleasure and displeasure people feel when they exercise
Alcohol ingestion impairs maximal post-exercise rates of protein synthesis
Consumption of a BCAA-containing sports beverage during 21km of running
Optimising performance through AI nutrition strategies
Peaking for the Olympic Games
I think you meant to say 25 in the title... You can delete this comment after!