PHYSIOLOGY: Gastrointestinal pathophysiology during endurance exercise: endocrine, microbiome, and nutritional influences
In this review, the authors "cover known factors that contribute to GI distress symptoms in athletes during exercise, while further attempting to identify novel avenues of future research to help elucidate mechanisms leading to symptomology". They note that GI issues are complex and multifactoral:
The etiology of gastrointestinal symptoms during endurance exercise is multi-factorial with neuroendocrine, microbial, and nutritional factors likely contributing to specific, individualized symptoms.
Recent work in previously unexplored areas of both microbiome and gut peptide secretion are pertinent areas for future work, and the numerous supplementation strategies explored to date have provided insight into physiological mechanisms that may be targetable to reduce the incidence and severity of gastrointestinal symptoms in athletes.
This supports the point raised in the introduction that:
Prolonged ischemia, mechanical damage to the epithelial lining, and loss of epithelial barrier integrity are likely contributors of gastrointestinal (GI) distress during bouts of endurance exercise.
PRACTICAL TAKEAWAY - take your time to identify and understand the causes of GI symptoms to develop your own nutritional strategy that accounts for these factors.
PACING: Fortune Favors the Brave: Tactical Behaviors in the Middle-Distance Running Events at the 2017 IAAF World Championships
This study set out "to assess tactical and performance factors associated with progression from qualification rounds in the 800-m and 1500-m running events at the 2017 International Association of Athletics Federations World Championships". The key findings were that:
Intermediate positioning and the ability to produce a fast final race segment are strongly related to advancement from qualification rounds in middle-distance running events.
The adoption of a more "risky" strategy characterized by higher speeds relative to season's best may be associated with an increased likelihood of qualification as fastest losers in the 1500-m event.
PRACTICAL TAKEAWAY - pacing is very dependent on the type of outcome being pursued: a fast race, qualification for the next round, winning. It's important to be aware of how your competitors may be pacing themselves and align your pacing strategy with your goal for each race.
In this study the authors "evaluated myonuclear distribution and organisation in endurance-trained wild-type mice and mice lacking PGC-1α in skeletal muscle (PGC-1α mKO)". This is important as PGC-1α is generally considered to be a critical component in adaptation to endurance exercise:
Endurance training triggers adaptive responses in skeletal muscle, including myonuclear accretion, decreased myonuclear domain (MND) sizes and increased expression of the transcription co-activator peroxisome proliferator-activated receptor-γ coactivator-1α (PGC-1α). Previous work has shown that overexpression of PGC-1α in skeletal muscle regulates mitochondrial biogenesis, myonuclear accretion and MND volume.
The authors explain their results as showing that:
Our findings suggest that PGC-1α is an important contributor to myonuclear accretion following moderate-intensity endurance training.
This may contribute to the adaptive response to endurance training by enabling a sufficient rate of transcription of genes required for mitochondrial biogenesis.
PRACTICAL TAKEAWAY - it can be useful to understand the mechanisms of adapation to help develop training protocols. In this case we have learned that PGC-1α is critical for endurance performance adaptations.
HEAT: A comparison of heat acclimation by post-exercise hot water immersion and exercise in the heat
This study set out "to compare heat acclimation adaptations after three and six days of either post-exercise hot water immersion (HWI) or exercise-heat-acclimation (EHA) in recreationally active individuals". The study methodology involved:
Post-exercise HWI involved a daily 40-min treadmill-run at 65% V̇O2peak in temperate conditions (19 °C, 45% RH) followed by HWI (≤40 min, 40 °C water; n = 9). Daily EHA involved a ≤60-min treadmill-run in the heat (65% V̇O2peak; 33 °C, 40% RH; n = 9), chosen to elicit a similar endogenous thermal stimulus to HWI.
The findings were that:
Compared with conventional short-term exercise heat acclimation, short-term post-exercise hot water immersion elicited larger thermal adaptations.
PRACTICAL TAKEAWAY - if you only have a short period to acclimatize to the heat then hot-water immersion is more effective than exercising in the heat.
NUTRITION: Common questions and misconceptions about creatine supplementation: what does the scientific evidence really show?
If you'd like to learn more about creatine supplmentation, this uesful paper aims to answer the questions:
- Does creatine lead to water retention?
- Is creatine an anabolic steroid?
- Does creatine cause kidney damage/renal dysfunction?
- Does creatine cause hair loss / baldness?
- Does creatine lead to dehydration and muscle cramping?
- Is creatine harmful for children and adolescents?
- Does creatine increase fat mass?
- Is a creatine ‘loading-phase’ required?
- Is creatine beneficial for older adults?
- Is creatine only useful for resistance / power type activities?
- Is creatine only effective for males?
- Are other forms of creatine similar or superior to monohydrate and is creatine stable in solutions/beverages?
PRACTICAL TAKEAWAY - creatine is a valuable supplement and has many use cases.
COACHING: "Opinion and Fact, Perspective and Truth": Seeking Truthfulness and Integrity in Coaching and Coach Education
An interesting paper pointing out some important considerations for new coaches and coaches susceptible to BS:
We consider some of the reasons why and argue that an emphasis on the development of critical and analytical thinking, as well as a scepticism towards the sources of information, would be a positive step against coach susceptibility to BS.
PRACTICAL TAKEAWAY - the authors' conclusion neatly sums up their thoughts: "we encourage more critical consumption of the “knowledge” available, we present a checklist to help coaches assess the veracity of claims and sift through the noise of the coaching landscape".