RESEARCH: studies shared from 9 to 15 Jan 2023

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.

This week's quick summary:

  • threshold between the heavy and severe intensity domains
  • types of running shoes and prevention of running injuries
  • effects of capsaicin on endurance performance
  • psychological state during a period of overreaching
  • a one-day CHO loading protocol

PHYSIOLOGY: Grey Zone: a gap between heavy and severe exercise domain


  1. The aim of this study was to determine a critical threshold (CT) interpreted as “the highest exercise intensity where V̇o2 can be stabilized before reaching 95% of V̇o2max (V̇o2peak)” and compare it with commonly used anaerobic threshold indices.
    • Ventilatory threshold (VT) was determined from incremental tests.
    • Multisession constant-load trials were performed to reveal V̇o2max.
    • Mathematically modeled critical power (CP) was estimated through the best individual fit parameter method.
    • Maximal lactate steady state (MLSS) was detected by 30-minute constant-load exercises.
    • The individual CT load of each cyclist was tested by constant-load exercises to exhaustion with +15 W intervals until minimal power output to elicit V̇o2peak.
  2. The results showed that work rate corresponding to CT was significantly greater than that of the MLSS, VT, and CP, and CP overestimated both VT and MLSS.
  3. In conclusion, this study indicates that there is a “grey zone” between heavy and severe exercise domain.


There are multiple different thresholds that could be used to separate the heavy and severe exercise domains. In addition, there can be slight variations based on the testing protocols and also variations in the values from day to day. I would suggest using these thresholds as guidelines and not being too strict or concerned about the absolute values.
In general, I think it's best to focus on training based on the our physiology markers (such as these thresholds) during the base season and certain blocks of training, and then shifting focus to the demands of the race and race pace in season.

EQUIPMENT: Running shoes for preventing lower limb running injuries in adults


  1. To assess the effects (benefits and harms) of running shoes for preventing lower‐limb running injuries in adult runners.
  2. We included 12 trials in the analysis which included a total of 11,240 participants, in trials that lasted from 6 to 26 weeks and were carried out in North America, Europe, Australia and South Africa.
  3. Results showed that:
    • Neutral/cushioned shoes may make little or no difference compared with minimalist shoes.
    • It is uncertain whether or not motion control shoes reduce the number injuries when compared to neutral shoes.
    • Soft midsole shoes may make little or no difference when compared with hard midsole shoes.
    • It is uncertain whether or not motion control shoes reduce injuries when compared with neutral / cushioned shoes.
    • Soft midsole shoes may make little or no difference to injuries when compared with hard midsole shoes.
    • It is uncertain whether or not stability shoes reduce injuries when compared with neutral/cushioned shoes.
    • It is uncertain whether or not motion control shoes reduce injuries when compared with stability shoes.
    • There was no evidence that running shoes prescribed based on static foot posture reduced the number of injuries compared with those who received a shoe not prescribed based on foot posture.
  4. Most evidence demonstrates no reduction in lower‐limb running injuries in adults when comparing different types of running shoes.


There does not appear to be enough evidence to suggest that a certain type of running shoe will prevent lower-limb running injuries. I would recommend choosing the shoes that feel most comfortable for each runner.

SUPPLEMENT: Effects of capsaicin and capsiate on endurance performance

I have shared one study about the use of capsaicinoid as an ergogenic aid which showed benefits of 12 mg of capsiate ingestion on endurance and resistance exercise. This meta analysis aimed to provide an overview of the current research on this supplement.


  1. Most studies provided capsaicin or capsiate in the dose of 12 mg, 45 min before exercise.
  2. In the meta-analysis for aerobic endurance, there was no significant difference between the placebo and capsaicin/capsiate conditions.
  3. In subgroup meta-analyses, there were no significant differences between the placebo and capsaicin/capsiate conditions when analyzing only studies that used time-trials or time-to-exhaustion tests.
  4. In the meta-analysis for muscular endurance, a significant ergogenic effect of capsaicin/capsiate was found
  5. Capsaicin/capsiate ingestion reduced RPE following muscular endurance but not aerobic endurance tests.


Capsaicin supplementation appears to benefit muscular endurance training rather than aerobic endurance training. Therefore, it would be worth testing it for muscular endurance training session such as weighted vest climbs for trail runners, torque training for cyclists, and resistance training in the gym. The recommended does is 12mg of capsaicin 45' before exercise.

PSYCHOLOGY: Effect of intensified training on cognitive function, psychological state & performance in trained cyclists

Two studies I've shared in past (monitoring of psychological mood disturbances, and, stress of the competition could trigger a negative mood profile) which showed the importance of mood as one of the markers that can be used to assess adaptation and how athletes are coping with training load. This study looked at cognitive function and psychological state in an overreaching period before a taper.


  1. Twenty-three trained male cyclists were randomly assigned to an intensified training group or a control group for two-weeks, followed by a two-week taper period.
  2. At baseline, one-week, two-weeks and post-taper, participants undertook a series of cognitive, performance, mood and recovery-stress assessments.
  3. The training intervention significantly increased training volume, load and strain by 108%, 116% and 151% respectively.
  4. Peak and mean power output on a maximal test and time trial significantly decreased by 4.8% and 9.4% following the two-week training intervention compared to baseline, in addition to a 169% change in total mood disturbance and significant disruption to recovery-stress balance.
  5. Intensified training caused deteriorations in physical performance but did not influence cognitive measures.
  6. Mood and recovery-stress balance were negatively affected by intensified training but recovered back to baseline following a two-week taper at a reduced training volume.


A two-week overreaching period resulted in no impact on cognitive function and a significant impact on mood. This suggestions that mood (and perhaos motivation) can be a useful marker of overreaching status that needs to be followed by a taper period when leading into a race, or by a deload period if it occurs during a normal training cycle. A few days of irritability, lack of motivation, and general grumpiness may be an indication that some rest and recovery is required.

CHO: Carbohydrate loading in human muscle: an improved 1 day protocol


  1. It is generally acknowledged that even without a glycogen-depleting period of exercise, trained athletes can store maximal amounts of muscle glycogen if fed a carbohydrate-rich diet for 3 days.
  2. Eight endurance-trained male athletes were asked to eat 10 body mass of high-carbohydrate foods having a high glycaemic index over 3 days, while remaining physically inactive.
  3. Muscle biopsies were taken prior to carbohydrate loading and after 1 and 3 days of eating the carbohydrate-rich diet.
  4. Muscle glycogen content increased significantly from pre-loading levels of wet mass after only 1 day, and remained stable afterwards despite another 2 days of carbohydrate-rich diet.
  5. This indicated that only 1 day of high carbohydrate intake was required for glycogen stores to reach maximal levels in types I, IIa, and IIb muscle fibres.


A one-day carbohydrate-loading protocol appears to be sufficient to prepare for an endurance event. The amount of carbohydrate used in this study was 10g / kg.

When I shared this paper on Twitter there was a good discussion and plenty of useful input from coaches and nutritionists. I would recommend reading the thread to get some ideas of how this protocol has been applied practically.

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