RESEARCH: Studies reviewed this week: 07 December 2020 to 13 December 2020

TRAINING LOAD: Accelerometer Based Data Can Provide a Better Estimate of Cumulative Load During Running Compared to GPS Based Parameters

Monitoring training load is important to understand the demands training is making on your body. The simplest measures such as duration and distance are easy to track, but don't take account of intensity. Some metrics report a combination of duration and intensity to try and better estimate and compare training sessions (TSS, Relative Effort, TRIMP, etc). This study found that:

Only 70% of the cumulative loading per training session was explained by these spatiotemporal parameters [duration, distance, speed] and that using a generic program based on these parameters will result in a relative error of 26%.

The authors tested truck based accelerometers to measure ground reaction forces and the velocity of these forces to try and determine a more effective training load metric. They concluded that this is an interesting area to investigate, but that more work is needed:

Trunk based accelerometers could give a more accurate estimation of accumulated training load compared to more commonly used parameters such as speed, time, and duration. Using this wearable technology can increase insight in the role of change and progression of training load in the development of [running related injuries].

PRACTICAL TAKE AWAY - when you monitor and evaluate your training, be sure to consider additional loads and demands of training that may not be determined from typical GPS metrics. You may not be able to quantify these, but you can "feel" them and add this sensor input to how you evaluate training.

NUTRITION: In vitro ketone‐supported mitochondrial respiration is minimal when other substrates are readily available in cardiac and skeletal muscle

I'm quite interested in ketones as a potential fuel and I've shared a few previous studies that showed there wasn't any benefit to using them for performance (studies one, two, and three). This study set out to identify if the body can use ketones as fuel at the mitochondrial level.

The authors showed that:

We demonstrate in vitro that maximal mitochondrial respiration supported by ketone bodies is low when compared to carbohydrate‐derived substrates in the left ventricle and red gastrocnemius muscle from rodents, and in human skeletal muscle.
When considering intramuscular concentrations of ketone bodies and the presence of other carbohydrate and lipid substrates, biological rates of mitochondrial respiration supported by ketone bodies are predicted to be minimal.

PRACTICAL TAKE AWAY - it appears that ketones are not a preferential source of fuel especially when other nutrients are available. Right now, it doesn't seem like ketones are valuable for performance.

ALTITUDE: Cognitive Impairment During Combined Normobaric vs. Hypobaric and Normoxic vs. Hypoxic Acute Exposure

This study set out to understand the effect of simulated altitude versus actual altitude on cognitive performance. Hypobaric hypoxia (HH) is actual altitude, while normobaric hypoxia (NH) is simulated altitude. The authors explain that "exposure to hypoxia has a deleterious effect on cognitive function; however, the putative effect of hypobaria remains unclear".

The results showed that:

Cognitive performance was decreased similarly in acute NH and HH. The [Cerebral oxygen delivery] reduction in NH and HH implies insufficient [middle cerebral artery blood flow velocity] increase to ensure cognitive performance maintenance. The present study suggests negligible hypobaric influence on cognitive performance in hypoxia and normoxia.

PRACTICAL TAKE AWAY - while cognitive function is impacted by altitude, there are not particular impacts of simulated altitude.

NUTRITION: Dietary Adjustments to Altitude Training in Elite Endurance Athletes; Impact of a Randomized Clinical Trial With Antioxidant-Rich Foods

My favorite types of studies look at what elite athletes actually do (I know this is not necessarily the best scientific process, but it feels practical and useful to me). In this study the authors set out to investigate "whether athletes adjust their dietary intake according to the IOC's altitude-specific dietary recommendations, and whether an in-between meal intervention with antioxidant-rich foods altered the athletes' dietary composition and nutrition-related blood parameters".

The key findings of the paper were:

  • At altitude the athletes increased their energy intake by 35%, the provided snacks accounting for 70% of this increase.
  • Carbohydrate intake increased from 6.5 ± 1.8 g/kg body weight (BW) to 9.3 ± 2.1 g/kg BW.
  • Dietary iron, fluid, and antioxidant-rich food intake increased by 37, 38, and 104%, respectively, in the whole cohort.
  • Experienced elite endurance athletes increased their daily energy, carbohydrate, iron, fluid, and antioxidant-rich food intake during a 3-week training camp at moderate altitude meeting most of the altitude-specific dietary recommendations.

PRACTICAL TAKE AWAY - increase your nutrition at altitude following the the IOC's dietary recommendations.

EQUIPMENT: The Optimal Weight Carriage System for Runners: Comparison Between Handheld Water Bottles, Waist Belts, and Backpacks

This study set out to determine the optimal way to carry water. Using 1kg of water weight in either a hand-held bottle, a waist belt, or a backpack, the authors tested the running economy across a range of variables. They found that:

Our results showed that economy deteriorated over time across all systems; however, no one single system was more economic, suggesting that during a 60-min run, at submaximal running speed, with a load of 1.0 kg the choice of carriage system has no significant influence on economy, HR, lactate, or RPE.

This led the authors to conclude that:

We recommend that in the absence of significant differences in economy the runner selects the carriage system based on personal preference.

PRACTICAL TAKE AWAY - it appears that the modality of carrying water does not affect economy. I would suggest choosing a method that you're accustomed to and that fits your race demands.

EQUIPMENT: Running With Various Loads Causes Change in Subjective and Objective Physiological Variables: 875

This study from 2010 investigated all three hydration options: one hand-held bottle, two hand-held bottles and a hydration pack. The authors looked at the impact on heart rate, rate of perceived exertion, VO2 Max demand, ventilation rate, and respiratory exchange ratio. On all of the variables except for the respiratory exchange ratio, the two hand-held bottles option performed the worst. A useful note with regards to the pack used in the study was its weight which was 1.4kg greater than the two hand-held bottles options. With the newer packs there is definitely less cost for the weight of the pack now. This led the authors to the conclusion that:

In order to optimize racing an ultra marathon, participants should strive to carry light loads close to their body (i.e. mid section or center mass) and attempt to give up weight later in a long race if pacers are allowed.

PRACTICAL TAKE AWAY - this is a slightly different result to the previous study above, suggesting that packs are more optimal than hand-helds.

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