RESEARCH: Studies reviewed this week: 04 January 2021 to 10 January 2021

ALTITUDE: Red cell volume expansion at altitude

I have shared a number of resources on altitude in the past and I believe that it is a useful training tool to improve performance. There are general guidelines on what altitude dose is necessary for acclimation with some rules of thumb including 11 days for each 1000m or a more generic 3-4 weeks recommendations for most training camps. This meta-review looked at both the time course and elevation for altitude responses.

The authors found:

Exposure time must exceed 2 wk at an altitude of more than 4000m to exert a statistically significant effect.

At lower altitudes, longer exposure times are needed with altitudes lower than 3000m not yielding an increase within 4 wk.

PRACTICAL TAKEAWAY - These altitudes and exposure periods are higher than those typically recommended for endurance athletes (~4wks at ~2500m). It may be worth keeping that in mind if you're not seeing the response you want from altitude training.

TRAINING: Calculation of Critical Speed from Raw Training Data in Recreational Marathon Runners

The idea of being able to calculate metrics that can be used to guide training from data collected in training appeals to me. Each athlete has a large set of data already available and it is current (rather than a test from months ago). This study set out to determine whether or not critical speed (CS) could be determined from runners' training data.

The authors found that:

CS and D′ determined from a large data set of raw training data may be useful to predict marathon performance and pacing.

PRACTICAL TAKEAWAY - while these types of calculations are not yet perfect, it's worth noting when this kind of analysis is available in your training log software and making the most of it.

HEAT: Running at Increasing Intensities in the Heat Induces Transient Gut Perturbations

One of the primary performance-limiting issues in ultramarathon running is nausea and vomiting and this often seems to be even worse in hot conditions. This study set out "to quantify...changes in gut permeability and lipopolysaccharides (LPS) translocation during...exercise under heat stress".

The testing protocol used quite high intensities which is not that common in studies:

2 treadmill runs of 2 × 15-minutes at 60% and 75% VO2max and up to 8 × 1-minutes at 95% VO2max in HOT (34°C, 68% relative humidity) and COOL (18°C, 57% relative humidity) conditions.

The findings of the study were that:

Both LPS and intestinal fatty acid-binding protein increased in hot conditions leading the authors to conclude that these results indicate a capacity to tolerate acute, transient intestinal disturbance in well-trained endurance runners.

PRACTICAL TAKEAWAY - While the study does not look at changes over time, it does appear that well-trained runners can handle the heat when it comes to stomach issues. Therefore, make sure you're a "well-trained" runner and practice running in hot conditions if you expect those on race day.

TRAINING: Does polarized training improve performance in recreational runners?

I have shared a couple of studies previously about polarized training: this one comparing polarized and pyramidal training, and, this one looking at the same think in half-ironman athletes. In my notes for both of those studies I suggested that the key point was to perform large amounts of training below VT1 and smaller amounts at higher intensities (the intensity here is dependent on the demands of the event being prepared for).

One question that often comes up when talking about polarized training is whether or not it applies to recreational runners who do a much smaller training load. This study set out to test a polarized or a between-thresholds training intervention on recreational runners. The test protocols and results showed:

The polarized group performed their 10 weeks of training with a distribution of 77%, 3%, 20% while the between-thresholds group had a distribution of 46%, 35%, 19%.

In a 10km TT both groups improved with the polarized group doing slightly better: 5.0% vs 3.6%.

PRACTICAL TAKEAWAY - While the difference in improvement was not significant between the two approaches, it does show that polarized training is not detrimental in that group of athletes. Therefore a polarized approach can be applied to athletes doing a smaller volume of training.

HEAT: Gastric emptying during exercise: Effects of heat stress and hypohydration

In the study above I noted the effect of heat on stomach issues. In this study the authors looked at the impact of heat on gastric emptying. The key outcomes of the study were that:

1. Exercise in a hot (49 degrees C) environment impairs gastric emptying rate as compared with a neutral (18 degrees C) environment;
2. Exercise in a warm (35 degrees C) environment does not significantly reduce gastric emptying before or after heat acclimation, but
3. Exercise in a warm environment (35 degrees C) when hypohydrated reduces gastric emptying rate and stomach secretions.

Reductions in gastric emptying appear to be related to the severity of the thermal strain induced by an exercise/heat stress.

PRACTICAL TAKEAWAY - it's important to understand the impact heat has on your performance and account for it in your race nutrition plans.

NUTRITION: International society of sports nutrition position stand: caffeine and exercise performance

I have shared multiple different papers on caffeine (see the Resources page) and it is clearly an ergogenic aid for endurance athletes. This superb position paper includes everything you need to know about caffeine.

A few points that I highlighted from this paper were:

• Aerobic endurance appears to be the form of exercise with the most consistent moderate-to-large benefits from caffeine use.
• Caffeine has consistently been shown to improve exercise performance when consumed in doses of 3–6 mg/kg body mass.
• The most commonly used timing of caffeine supplementation is 60 min pre-exercise.
• Caffeine may improve cognitive and physical performance in some individuals under conditions of sleep deprivation.
• The use of caffeine in conjunction with endurance exercise in the heat and at altitude is well supported when dosages range from 3 to 6 mg/kg and 4–6 mg/kg, respectively.

PRACTICAL TAKEAWAY - clearly caffeine is a supplement that you should be considering for sports performance. I highly recommend reading this position paper to learn the mechanisms and best practices.