RESEARCH: Studies reviewed this week: 14 June 2021 to 20 June 2021

TRAINING: Endurance Is Improved in Female Rats After Living High-Training High Despite Alterations in Skeletal Muscle

I've shared a large range of studies on the benefits of altitude (available on the resources page). This study investigated a different component to the normal review of blood parameters as the authors "hypothesized that living and training at high altitude (LHTH) improves mitochondrial efficiency and/or substrate utilization". In a study looking at female rats living at altitude for 5 weeks, the authors found that:

Maximal aerobic velocity (MAV) improved with training, independently of hypoxia, whereas the time to exhaustion, performed at 65% of MAV, increased both with training and hypoxia, with an additive effect of the two conditions.
The hematocrit increased >20% with hypoxia.
The increases in mitochondrial mass and maximal oxidative capacity with endurance training were blunted by combination with hypoxia.

This led the authors to conclude that:

Our results show that mitochondrial adaptations are not involved in the improvement of submaximal aerobic performance after LHTH, suggesting that the benefits of altitude camps in females relies essentially on other factors, such as the transitory elevation of hematocrit, and should be planned a few weeks before competition and not several months.

PRACTICAL TAKEAWAY - altitude training should be designed to make the most of the transitory elevation of hematocrit which means going on a training camp for 3-5 weeks close to the period of competition.

NUTRITION: The effect of dietary nitrate supplementation on high altitude exercise performance and adaptation during a military trekking expedition

Beetroot juice has been show to reduce the oxygen cost of exercise so it is often recommended as a ergogenic supplement for endurance sport. In this study the authors extend the current research to "investigate the effect of dietary nitrate supplementation for 20 days on salivary nitrite, exercise performance and high altitude (HA) acclimatisation in field conditions".

The protocol for the study involved:

Participants received two 70 ml dose per day of BRJ. Participants ingested supplement doses daily, beginning 3 days prior to departure and continued until the highest sleeping altitude (4800 m) reached on day 17 of the expedition.

The authors found that:

There was no decline in fitness scores at 4800 m compared with baseline in the BRJ group [compared to significant declines in the control group].
Heart rate recovery speed following exercise at 4800 m was significantly prolonged in the control group but was unchanged in the BRJ group.

PRACTICAL TAKEAWAY - beetroot juice can be used to decrease the decline in fitness at altitude.

NUTRITION: Pre-Sleep Casein Supplementation, Metabolism, and Appetite

A previous study I shared showed that pre-sleep casein did not affect next-day appetite and metabolism in older men (available here). This review looks into a similar issue to determine "the effect of this nutritional strategy on non-muscular parameters such as metabolism and appetite in both healthy and unhealthy populations".

The result of the systematic review showed:

Limited to no effects on metabolism or appetite when ingesting 24–48 g of casein 30 min before sleep.

PRACTICAL TAKEAWAY - pre-sleep casein protein can be beneficial for muscle protein synthesis and it will not affect your next-day appetite or metabolism.

HYDRATION: Whole-body fluid distribution in humans during dehydration and recovery, before and after humid-heat acclimation induced using controlled hyperthermia

I haven't heard of the idea of plasma volume being defended before so I was interest in this study which set out "to test the hypothesis that the plasma volume is not selectively defended during exercise- and heat-induced dehydration following humid-heat acclimation". The authors used a thorough protocol:

Inter-compartmental fluid losses and movements were tracked (radioisotopes and Evans blue dye) during progressive dehydration (cycling) in these same conditions and also during a resting recovery without fluid replacement (28 °C)

The results showed that:

Plasma volume was not defended more vigorously following humid-heat acclimation.
Indeed, a greater fluid loss may well underlie the mechanisms for enhancing plasma volume recovery when heat acclimation is induced using the controlled-hyperthermia technique.

PRACTICAL TAKEAWAY - dehydration can cause decreases in plasma volume even after acclimation so ensuring that you are adequately hydrated may be beneficial to performance. [I believe that decreasing plasma volume may be one of the causes of cardia drift during endurance exercise.]

HEAT: The effect of seasonal acclimatization on whole-body heat loss response during exercise in a hot humid environment with different air velocity

As we are finally heading into summer here I've been thinking about heat acclimation for some summer races. It makes perfect sense that our bodies are able to adapt to the seasonality of temperatures, however, this study points out that "seasonal acclimatization from winter to summer is known to enhance thermoeffector responses in hot-dry environments during exercise whilst its impact on sweat evaporation and core temperature (Tcore) responses in hot-humid environments remains unknown". The authors set out to address this gap in the research.

They found that:

Seasonal acclimatization enhanced whole-body sweat rate (WBSR), unevaporated sweat rate, local sweat rate and mean skin temperature compared to pre-acclimatization state whilst sweating efficiency was lower until the 55-min of exercise.
Seasonal acclimatization enhances thermoeffector responses but does not attenuate Tcore during exercise in a hot-humid environment.

PRACTICAL TAKEAWAY - our bodies will become acclimated to seasonal changes in heat and humidity, however, it may be important to plan races carefully to ensure that enough time is provided for this acclimation to happen before key races (otherwise include a deliberate intervention in your training).

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