RESEARCH: studies shared from 2 to 8 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:

• exercise intensity during different distances in mountain running races
• chronic CHO restriction improves ultra-endurance capacity
• long intervals followed by short intervals to accumulate time close to VO2max
• running uphill on a trail vs. a treadmill significantly elevates oxygen cost of running
• right ventricular changes in highly training athletes

PACING: Physiological demands of mountain running races

STUDY DETAILS

1. The aim of this study was to analyze the exercise intensity and competition load (PL) based on heart rate (HR) during different mountain running races.
2. Seven mountain runners participated in this study. They competed in vertical (VR), 10-25 km, 25-45 km and >45 km races.
3. The exercise intensity below ventilatory (VT) and between VT and respiratory compensation threshold (RCT) increased with mountain running race distance.
4. Likewise, the percentage of racing time spent above RCT decreased when race duration increased. However, the time spent above RCT was similar between races (~50 min).
5. This result was consistent with that found by Ramos-Campo et al. (2016) during a mountain ultramarathon (~50 min, ~13% of racing time) when analyzed an intensity zone >90% of HR reserve, which might be considered similar to zone 3.
6. We believe that runners regulated their effort at high-intensity in order to opti-mize their performance.

PRACTICAL TAKEAWAY

The change in the time in different zones as a percentage of total duration for each race is a result which I expected. However, the fact that athletes spent a similar amount of time (~50') above the second threshold for each races is an interesting outcome. I think this can fit in quite well with the analogy of "having matches to burn" during a longer race. Each "match" is a period of time above the second threshold and we can only sustain this for ~50'. Therefore, it's important to use these "matches" wisely during your races.

In response to this tweet, Jason Koop replied: "I have consistently observed (since 2005!) that many of the elite athletes I work with can have ~120 min of time above LT hr in a ~80k race. Much of this is dependent on how the climbs/descents are broken up." This provides additional support of the study results and suggests that time above threshold of > 50' is possible.

CHO: Chronic carbohydrate restriction improves endurance capacity and body composition in men and women

STUDY DETAILS

1. This study was designed to test whether adaptation to a CHO-restricted diet affects physical capacity during prolonged exercise.
2. Thirteen highly trained endurance athletes consumed a high (more than 5 g CHO/kg/day) or low (less than 2 g CHO/kg/day) carbohydrate training diet for four weeks in a randomized cross-over design.
3. Performance was measured after a 24 h high carbohydrate “loading” regime, through a self-paced time trial to complete a fixed workload equivalent to five hours at a workload calculated to elicit 55% VO2max.
4. Although time to completion was not significantly different between diets, the average absolute (watts) and relative (W/kg) power outputs were significantly better on the carbohydrate restricted diet.
5. Results from this study highlight that when carbohydrate is restricted during training, trained endurance athletes show improved ultra-endurance performance relative to their body mass.

PRACTICAL TAKEAWAY

A low CHO training diet appeared to improve performance during very low intensity endurance exercise (55% of VO2 Max). This diet may be beneficial for ultra-marathon runners who race at a low intensity. However, don't forget the pre-race CHO loading regime as this was an important part of the intervention.

INTERVALS: High-intensity interval training: optimizing oxygen consumption and time to exhaustion taking advantage of the exponential reconstitution behaviour of D’

STUDY DETAILS

1. The aims of this study were: (1) to verify whether postponing the first recovery interval improves time to exhaustion during a high-intensity interval training (HIIT) test, and (2) to verify whether a HIIT protocol with decreasing interval duration (HIDIT) is more effective in accumulating time near VO2max.
2. The subjects performed three trials with a single recovery interval after 30 s (Rec30s), after 3 min (Rec3min) and after exhaustion (RecTlim) to verify whether postponing the first recovery interval enhances the time to exhaustion.
3. Finally, the subjects performed the three HIIT protocols mentioned above.
4. The time to exhaustion was significantly greater in RecTlim than in Rec3min and Rec30s.
5. The time accumulated near VO2max was significantly longer in HIDIT than in SIHIIT and LIHIIT.
6. Training protocols starting with long intervals followed by short intervals could be useful to accumulate time close to VO2max and consequently improve it.

PRACTICAL TAKEAWAY

If your goal is to accumulate time close to VO2 Max, interval sessions that start a longer interval and then followed with shorter intervals appear optimal. Examples include:

• HIDIT intervals
• 3' fast / 2' easy; 12 x (30" fast / 15" easy)

After I shared this study on Twitter there was some good discussion on different was to manipulate intervals and a few good sessions mentioned by coaches in the thread. I'd encourage you to go there to read more.

ENVIRONMENT: Effect of ground technicity on cardio-respiratory and biomechanical parameters in uphill trail running

STUDY DETAILS

1. Ten experienced male trail-runners ran ∼10.5 min at racing pace on two trails with different (high and low) a priori technicity levels.
2. These two runs were replicated (same slope, velocity, and distance) indoor on a motor-driven treadmill.
3. Oxygen cost of running (O2Cr) (+10.5%), minute ventilation (V̇E) and the range and variability of feet medio-lateral accelerations, were significantly greater when running on trail compared to the treadmill, regardless of the a priori technicity level.
4. Despite perceived technicity being lower on treadmill, RPE was not different between trail and treadmill runs.
5. It is concluded that running uphill on a trail vs. a treadmill significantly elevates both O2Cr and magnitude/variability of feet medio-lateral accelerations but no difference could be identified between trails of different a priori technicities.

PRACTICAL TAKEAWAY

There is a significant cost to running uphill on technical trails (~10%) compared to running on the treadmill. It is important to consider this when calculating the demands of a trail race to design your training protocol and also to consider it when creating a race strategy. Additionally training on trails, regardless of how technical they are, is vital to prepare for trail races.

PHYSIOLOGY: Right Ventricular Changes in Highly Trained Athletes

STUDY DETAILS

1. Exercise causes structural, functional, and electrical changes of the heart which are physiological responses to the hemodynamic demands of increased cardiac output during exercise.
2. The main changes are represented by cardiac enlargement with preserved compliance and contractility such that, according to the law Laplace, “the larger heart can fill and empty larger volumes more efficiently.”
3. Indeed, while the reversibility of the changes induced by sport after detraining was considered a typical feature of athletes heart, several studies showed that recovery might be incomplete, in particular for RV changes and this is particularly true in more practiced athletes.
4. Right sided-valves (pulmonary and tricuspid) present a higher prevalence of regurgitation in athletes, possibly as a result of chambers enlargement due to the long-term overload caused by training.
5. Studies of endurance athletes following competitive events in different disciplines and of different durations have shown evidence of acute myocardial injury based on the transient elevation of biomarkers (Troponin and B-type natriuretic peptide) following these events.
6. There is now reasonably compelling evidence that some cardiac arrhythmias are associated with long-standing endurance training.
7. Biffi et al. reported that ventricular ectopic beats were common among athletes but was a benign and potentially reversible phenomenon so long as underlying cardiac disease was excluded.
8. The degree to which many years of intense endurance exercise promotes ventricular arrhythmias is yet to be determined.
9. It is unknown to what extent these issues are caused by sports practice in its own right as opposed to being an expression of an underlying familial predisposition such as ARVC.

PRACTICAL TAKEAWAY

Endurance exercise will definitely have an impact on an athlete's heart. There is evidence that athletes have some cardia arrhythmias and there can be acute myocardial injury following competitive events. However, the authors note that "there are a multitude of health benefits from exercise and these are very unlikely to be outweighed by any small risk of arrhythmias."

My suggestions would be to ensure that you do annual medical check-ups that are thorough (many races require a medical certificate now, so you may as well do a proper check-up) and that you give yourself time after big events to allow for recovery of any acute myocardial injuries.