RESEARCH: Studies from 19 to 25 Feb 24
Sharing research and insights from coaches, scientists and athletes to help us improve endurance performance.
This week’s quick summary:
Ground contact time, footstrike, and their impact on running economy
Sports bra restriction on respiratory breathing mechanics
Carbohydrate hydrogel for delivery of sodium bicarbonate mini-tablets
Associations between sleep and in-race gastrointestinal symptoms
What is the effect of paracetamol ingestion on exercise performance?
PHYSIOLOGY: Longer ground contact time is related to a superior running economy in highly trained distance runners
Most of the previous studies I’ve shared on running economy have focused on the benefit of supershoes, and how strength training and hopping exercises can improve running economy. In this study, the authors were looking into running form through the metrics of ground contact time and footstrike pattern. They set out “to investigate the relationship between running economy (RE), ground contact time, and thigh muscle cross-sectional area (CSA) in highly trained distance runners, comparing two habitual footstrike patterns”.
STUDY DETAILS
Seventeen male distance runners participated in treadmill running to measure RE and gait parameters.
Thigh muscle CSAs were collected via magnetic resonance imaging.
RE showed a significant negative correlation with distance running performance (r = -0.50) and ground contact time (r = -0.51).
Ground contact time demonstrated a significant negative correlation with normalized CSAs of vastus lateralis (r = -0.60) and hamstrings (r = -0.54).
No significant differences were observed in RE, ground contact time, or normalized CSAs between midfoot (n = 10) and rearfoot (n = 7) strikers.
PRACTICAL TAKEAWAY
There are a couple of interesting findings in this study, the first of which is that there is a benefit to greater ground contact time as it appears to be related to greater running economy. This was a result I didn’t expect, and I’m not sure that it is a result that can lead to a practical takeaway as I’m unaware of any training intervention designed to increase ground contact time. Nevertheless, this is a useful new way to consider the metric that some runners get from their watches and which they may never known how to interpret before.
The second interesting outcome is that footstrike pattern appears to have insignificant effects on RE. This indicates that highly trained runners can continue to use their natural footstrike pattern without performance detriment and without any concern about trying to change their patterns.
EQUIPMENT: Sports bra restriction on respiratory mechanics during exercise
This is a topic that I have never seen any research on so it’s fascinating to see a study looking into the impact of wearing a sport bra on breathing. In this study, the authors set out “to understand how underband tightness or pressure of a sports bra relates to respiratory function and the mechanical work of breathing”.
STUDY DETAILS
Nine highly trained female runners participated in maximal and submaximal running wearing sports bras of varying tightness: loose, self-selected, and tight.
During maximal exercise, tighter bras resulted in significantly greater mechanical work of breathing compared to looser ones.
Tight bras led to a 5% increase in minute ventilation compared to loose ones.
The breathing pattern differed between conditions, with tighter bras causing higher breathing frequency and lower tidal volume.
Submaximal running in tight bras increased oxygen uptake by 1.3 ± 1.1% compared to loose bras.
PRACTICAL TAKEAWAY
This study suggests that loosening the underband of a sports bra may decrease the work of breathing, promote deeper breaths, and improve running economy. This obviously needs to be balanced with the functional purpose of a sports bra of providing support and I believe it highlights the importance of selecting a properly fitting sports bra to optimize respiratory function during exercise.
The author of the study, Shalaya Kipp, replied to my question about the same concern of breathing restriction applying to chest straps by explaining that they saw similar results with firefighters wearing backpacks. This leads me to suggest a takeaway of making sure that athletes’ clothing and equipment (sports bra, chest strap, backpack) fit appropriately and in particular athletes wearing multiple layers of these products during running need to be careful in impacting their breathing.
SUPPLEMENT: The effects of a carbohydrate hydrogel system for the delivery of bicarbonate mini-tablets on acid–base buffering and gastrointestinal symptoms in resting well-trained male cyclists
A previous study I shared on sodium bicarbonate showed that it is beneficial for muscular endurance training. However, another study I shared showed that it was only ergogenic when removing participants from the study who suffered GI issues. In my practical takeaway for this second study, I reported a few anecdotes and stories from athletes who struggled with these GI issues. For this reason, the Maurten Bicarb system which promises to remove these GI issues is promising. In this study, the authors set out “to investigate the effects of a new sodium bicarbonate (SB) supplement, marketed as the "Bicarb System," on acid–base balance and gastrointestinal (GI) discomfort in well-trained male cyclists”.
STUDY DETAILS
Twelve well-trained male cyclists participated in a randomised crossover study.
Participants ingested either the “Bicarb system” (M-SB) or vegetarian capsules sodium bicarbonate (C-SB) supplement in randomised order.
Blood samples were collected every 30 minutes for pH, bicarbonate (HCO3−), and electrolyte measurements for 300 minutes.
Peak HCO3− levels were significantly higher with M-SB, achieved earlier, and sustained for a longer duration compared to C-SB.
GI discomfort was significantly reduced with M-SB ingestion compared to C-SB, with reductions observed in stomach cramps, bowel urgency, diarrhoea, belching, and stomach-ache.
PRACTICAL TAKEAWAY
The results of this study suggest that the "Bicarb System" supplement demonstrated the ability to enhance buffering capacity while significantly reducing GI discomfort in well-trained male cyclists. The results do not necessarily show a performance improvement as the focus was on GI issues, but we can rely on previous research that suggests that sodium bicarbonate can be beneficial for performance (in particular during sprints or events including surges and sprints). My recommendation for athletes who are considering using sodium bicarbonate is to use the Maurten Bicarb System, but of course to test it in training before using it in a race.
SLEEP: Associations between sleep and in-race gastrointestinal symptoms: an observational study of running and triathlon race competitors
I have shared a number of studies showing the negative impact of sleep deprivation on training and performance (see SLEEP section in my archives). In this study, the author set out “to investigate the potential link between poor sleep and gastrointestinal (GI) issues in athletes”.
STUDY DETAILS
87 race participants completed questionnaires assessing sleep problems and reported GI symptoms severity during races.
Spearman's correlations showed a correlation between Sleep Problems Index-I (SPI-I) scores and in-race upper GI symptoms.
Controlling for anxiety weakened this association, with other variables having minimal impact.
Acute sleep quantity and quality didn't correlate with GI symptoms during races.
The study concluded that chronic sleep issues moderately correlate with in-race upper GI symptoms, suggesting a need for further investigation into potential mediating factors like anxiety.
PRACTICAL TAKEAWAY
I’m not sure I was aware of the potential link between sleep and GI issues, but the author pointed out that these findings agree with research in the general population that has found associations between chronic sleep problems and GI disturbances. While the link between the two is weakened when considering anxiety, it seems that there is enough association for athletes to consider sleep if they are suffering with GI during races. As the author explains, “perhaps the best explanation for these observations is that each GI symptom has multiple potential causes, and any single variable is likely to explain only a relatively small proportion of the observed variance in GI symptomology”. My recommendation is that when trying to resolve GI issues, athletes should perform a multi-factorial investigation which also includes looking at the quality of their sleep.
SUPPLEMENT: What is the effect of paracetamol (acetaminophen) ingestion on exercise performance?
I have shared one study on pain medication, a study on ibuprofen that showed no benefit for athletes. Given the potential risks of using ibuprofen during exercise, I do not recommend it. Another common pain medication that athletes take due to purported benefits for endurance is paracetamol. In this opinion piece, the author set out “to shed light on paracetamol's impact on endurance, sprinting, and resistance exercise performance”.
STUDY DETAILS
Paracetamol ingestion 45–60 minutes pre-exercise shows ergogenic potential for endurance performance.
Endurance benefits are more pronounced in time-to-exhaustion tests than time-trials.
Ingesting paracetamol 30 minutes pre-exercise increases mean power during repeated cycling sprints in interval training.
Initial data suggest paracetamol may enhance endurance in heat, improve single sprint performance post-fatigue, and attenuate strength decline during repeated maximum contractions.
A dose of 1500mg taken 30–60 minutes pre-exercise yields the most consistent ergogenic effects.
PRACTICAL TAKEAWAY
This study suggests that ingesting 1500mg of paracetamol 30–60 minutes before exercise may provide potential performance enhancement, particularly in endurance and interval training. I have highlighted the endurance benefits, but there are further details about resistance and sprint training in the review. It is important to note the author’s final recommendation which is what I would emphasize: “Despite these performance-enhancing effects, the aim of this article is not to promote paracetamol use, as side effects associated with its consumption and ethical aspects need to be considered before utilizing paracetamol as an ergogenic aid”.
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:
Overtraining syndrome and relative energy deficiency in sports
Hazard of deceptive advertising of footwear
Beta-alanine supplementation for cycling performance
Force production during maximal front crawl swimming
Regulation of muscle glycogen metabolism during exercise
Killer work as always.