RESEARCH: Studies reviewed this week: 21 December 2020 to 27 December 2020

HEAT: Changes in the physiological strain and graded exercise performance due to warming or cooling of the lower body in a temperate environment

How much does the temperature of exercising muscles affect the performance in a temperate environment. This study set out to determine this by putting subjects through a series of trials with muscle temperatures adjusted to 31C (cold), 33C (cool), 35C (warm) or 37C (hot) using water-perfusion pants. The authors found that:

No significant differences were observed in the V̇O2peak or TTE among the 4 conditions; however, the HR, Tb, and total sweat loss were significantly higher under warming conditions than cooling conditions.

PRACTICAL TAKE AWAY - these results suggest that even though the strain on the muscles is greater at higher temperatures, the muscle temperature does not affect performance. If you are racing in hot conditions, it is important to take this into consideration (for multiple reasons), but probably is unnecessary to try and artificial cool the legs for any other benefit other than RPE.

TRAINING: Session Rating of Perceived Exertion Combined With Training Volume for Estimating Training Responses in Runners

I've shared four different studies in the past looking at training load metrics (available on the resources page). This study looks at the topic again this time assessing "week-to-week changes in the training loads of recreational runners using different quantification methods".

The authors looked at a series of different metrics: running time, steps, cumulate shock as well as multiples of these metrics and corresponding RPE values. They found that:

Use of an internal training-load measure (sRPE) in combination with external load (training duration) provided a more individualized estimate of week-to-week changes in overall training stress.
We therefore recommend the regular use of sRPE and training duration to monitor training load in runners.

PRACTICAL TAKE AWAY - measuring load using session RPE and duration is a useful means of tracking training load.

NUTRITION: Lower nocturnal blood glucose response to a potato-based mixed evening meal compared to rice in individuals with type 2 diabetes

This is a simple and effective study trying to understand the blood glucose impact of different carbohydrates. The authors compared boiled, roasted, boiled and cooled potatoes, and rice to see the postprandial insulin impact and the nocturnal glucose impact. The authors found that:

No significant differences between CONTROL and BOIL or ROAST were detected for postprandial insulin concentrations. All potato meals resulted in lower nocturnal glucose than CONTROL.

PRACTICAL TAKE AWAY - potatoes may be a good option if you're looking to control your overnight glucose levels.

NUTRITION: Ultra-Processed Diets Cause Excess Calorie Intake and Weight Gain

In a clarification of a previous study, these authors highlighted the significant impact of an ultra-processed diet on calorie intake:

The ultra-processed diet resulted in increased energy intake at breakfast, lunch, and dinner as compared to the unprocessed diet. Carbohydrate intake was significantly increased during the ultra-processed diet at breakfast, lunch, and dinner. Fat intake was significantly increased during the ultra-processed diet at breakfast and lunch, and tended to be increased at dinner. Protein intake was significantly lower during the ultra-processed diet at lunch but was not significantly different from other meals.

PRACTICAL TAKE AWAY - an ultra-processed diet resulted in an increase in daily calories consumed of ~500kCal. Be very careful when choosing ultra-processed foods and when including them in your diet.

SLEEP: Reciprocal Associations Between Sleep, Mental Strain, and Training Load in Junior Endurance Athletes and the Role of Poor Subjective Sleep Quality

This study "investigates reciprocal associations between sleep, mental strain, and training load by utilizing a prospective, observational design". I appreciate that the idea is to understand how these components interact as it is generally accepted that sleep anxiety can reduce sleep quality, but there isn't much data available in the research.

Te authors found that:

The results show that increases in mental strain are associated with decreased total sleep time, light sleep, and sleep efficiency. Further, both mental strain and training load are associated with subsequent deceased rapid eye movement sleep. Increases in total sleep time, light, deep, and REM sleep are all associated with subsequent decreased training load.

PRACTICAL TAKE AWAY - training can have a negative impact on sleep quality and time. If you have a high training load and your sleep is of lower quality than usual, it may be worth reducing the load slightly to improve sleep quality and enhance recovery.

TRAINING: Deliberate practice in training differentiates the best Kenyan and Spanish long-distance runners

The aim of this study was to compare "the amount of systematic training and the different training activities undertaken by elite-standard long-distance runners during their first seven years of systematic training". Three different levels of athletes were examined with the authors identifying the following key factors of the highest level athletes:

As part of an overall higher accumulation of distance run, the Kenyans [the highest level athletes in the study] completed more tempo runs and short-interval training than the other groups, but did not complete more long intervals or races.

PRACTICAL TAKE AWAY - in addition to training higher volumes, the key features of the best runners' training is tempo runs and short intervals.

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