RESEARCH: studies I shared this week: 19 to 25 December 2022

All of the studies I've shared (~600 studies) are available on the RESOURCES PAGE.

This weekly summary is also available in my Substack newsletter - Endurance: Ideas + Implementation.


  • drinks, gels, chews can all be used interchangeably at 120g/hr.
  • low-glycaemic, high-CHO diet may be optimal for performance.
  • maintaining downhill pace late in ultras results in better performance.
  • one in five people meet minimum exercise guidelines
  • exogenous ketosis may cause suppressed diuresis.

NUTRITION: CHO - 13C-glucose-fructose labeling reveals comparable exogenous CHO oxidation during exercise when consuming 120 g/h in fluid, gel, jelly chew, or coingestion


  1. We examined the effects of carbohydrate (CHO) delivery form on exogenous CHO oxidation, gastrointestinal discomfort, and exercise capacity.
  2. Nine trained males ingested 120 g CHO·h−1 from fluid (DRINK), semisolid gel (GEL), solid jelly chew (CHEW), or a coingestion approach (MIX).
  3. Participants cycled for 180 min at 95% lactate threshold, followed by an exercise capacity test (150% lactate threshold).
  4. Exercise capacity was also not significantly different between conditions.
  5. We conclude that 120 g·h−1 CHO (in a 1:0.8 ratio of maltodextrin or glucose to fructose) is a practically tolerable strategy to promote high CHO availability and oxidation during exercise.

PRACTICAL TAKEAWAY - I've seen previous research using 2:1 glucose: fructose at a rate of 108g/hr which showed that bars, gels and drinks can be mixed and matched (see Asker Jeukendrup's post). This study proves that relationship holds up at even higher rates of CHO/hr. Therefore, use the type of CHO that you find most palatable and easy to use.

CHO: A high carbohydrate diet with a low glycaemic index improves training effects in male endurance athletes


  1. The present study investigated the effect of a 4-week high-fat low-carbohydrate (HFLC-G) versus high-carbohydrate low-glycaemic (LGI-G) or high-glycaemic (HGI-G) diet on power output at lactate thresholds, peak oxygen uptake and peak performance during an incremental cycle test in 28 male endurance athletes.
  2. All participants showed improved levels of power output at the lactate thresholds with a more pronounced effect in the HFLC-G and LGI-G.
  3. In the HFLC-G peak performance decreased, while in the LGI-G and HGI-G peak performance increased.
  4. To our best knowledge, this is the first study comparing a high-fat nutrition and carbohydrate-rich diets with different GI on performance-related outcomes.
  5. In contrast a low-glycaemic diet seem to be of advantage in both endurance scenarios: submaximal and high intensity.

PRACTICAL TAKEAWAY - it appears that aiming for a low-glycaemic, but high-CHO diet may be an optimal diet for performance.

PACING: Downhill Sections Are Crucial for Performance in Trail Running Ultramarathons


  1. Pacing strategy, i.e., how athletes modulate running speed for managing their energies during a race, appears to have a significant impact on overall performance.
  2. The aims of this study were to investigate whether performance level, terrain (i.e., uphill or downhill) and race stage affect pacing strategy and whether any interactions between these factors are evident.
  3. Better finishers (i.e., athletes ranking in the best positions) tend to run downhill sections at higher relative speeds and uphill sections at lower relative speeds than slower counterparts
  4. In the later race stages, the relative speed decrease is larger in downhill sections than in uphill one and in downhill sections, slower finishers perform systematically worse than faster ones.
  5. In conclusion, running downhill sections at higher relative speeds, most likely due to less accentuated fatigue effects, as well as minimizing performance decrease in the later race stages in downhill sections, appears to be a hallmark of the better finishers.

PRACTICAL TAKEAWAY - this study complements the research I shared last week that showed that conservative uphill pacing results in better performance. The descents are a critical aspect of a race and the ability to hold the pace later in a race appears to result in superior performances. Together, conservative uphills and fast downhills, appear to be best way to pace mountainous races.

HEALTH: Adherence to aerobic and muscle-strengthening activities guidelines


  1. To estimate the global prevalence of meeting the WHO guidelines for both aerobic and muscle-strengthening activities (MSA) in populations aged ≥5 years, and whenever possible to explore this prevalence according to sociodemographic and lifestyle factors.
  2. Twenty-one studies comprising 3 390 001 individuals from 32 countries were included.
  3. Overall adherence to the aerobic and MSA guidelines was 17.12% in adults ≥18 years.
  4. Among adolescents aged 12–17 years, adherence to both guidelines was 19.74%.
  5. Only one out of five adolescents and adults met the recommended combined aerobic and MSA guidelines.

PRACTICAL TAKEAWAY - most readers of this newsletter are athletes, however, not all athletes train forever and we all have family members who don't train seriously. It's important to make sure that we know what the minimum exercise guidelines are and that we still meet them for our long-term health.

NUTRITION: Exogenous ketosis suppresses diuresis and atrial natriuretic peptide during exercise


  1. We investigated whether acute exogenous ketosis by oral ingestion of ketone ester (KE) during a simulated cycling race (RACE) affects the hormonal pathways implicated in fluid balance regulation during exercise.
  2. In a double-blind crossover design, 11 well-trained male cyclists participated in RACE consisting of a 3-h submaximal intermittent cycling (IMT180') bout followed by a 15-min time trial (TT15') in an environmental chamber set at 28°C and 60% relative humidity.
  3. Before and during RACE, the subjects received either a control drink (CON) or the ketone ester (R)-3-hydroxybutyl (R)-3-hydroxybutyrate (KE), which elevated blood β-hydroxybutyrate to ∼2-4 mM.
  4. Urine output during IMT180' was ∼20% lower in KE (1,172 ± 557 mL) than in CON and KE also raised plasma noradrenaline concentrations during RACE.
  5. Exogenous ketosis suppresses diuresis and downregulates NT-pro ANP secretion during exercise.

PRACTICAL TAKEAWAY - research papers I've shared in the past do not support the use of ketones (ketone ingestions impaires cycling TT performance, has no benefit for running time trial, increases cardiovascular stress, and impairs race walk performance). I'm not yet sure what the implications of suppressed diuresis are, however, it's important to be aware of any potential disruptions when taking ketones and this impact would be an important one to consider.

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