RESEARCH: Studies reviewed this week: 13 December 2021 to 19 December 2021

NUTRITION: Nutritional approaches to counter performance constraints in high-level sports competition

Louise Burke has done incredible research on sports nutrition for years. It's always valuable to read her thoughts and to learn from her. The goal of this paper is to highlight that:

A range of nutritional strategies can be used by competitive athletes, alone or in combination, to address various event-specific factors that constrain event performance. Evidence for such practices is constantly evolving but must be combined with understanding of the complexities of real-life sport for optimal implementation.

PRACTICAL TAKEAWAY - read this paper!

NUTRITION: Caffeine Increases Exercise Performance, Maximal Oxygen Uptake, and Oxygen Deficit in Elite Male Endurance Athletes

I've shared multiple papers of the benefit of caffeine on performance (search for caffeine on my resources page). This study set out to test "the hypothesis that caffeine increases maximal oxygen uptake (V˙O2max) and to characterize the physiological mechanisms underpinning improved high-intensity endurance capacity".

In a quite thorough test protocol where athletes ran to exhaustion during an incremental test (running 10.5° incline, start speed 10.0 km·h−1, and 0.5 km·h−1 increase in speed every 30 s) after either taking caffeine (4.5 mg·kg−1) or placebo 45 min before standardized warm-up. The results showed that:

Caffeine increased time to exhaustion from 355 ± 41 to 375 ± 41 s. Importantly, caffeine increased V˙O2max from 75.8 ± 5.6 to 76.7 ± 6.0 mL·kg−1·min−1.
The increase in time to exhaustion after caffeine ingestion was reduced to 11.7 s after adjustment for the increase in V˙O2max.
Caffeine did not significantly increase V˙O2max after adjustment for VEpeak and HRpeak.

PRACTICAL TAKEAWAY - while it appears unclear that the caffeine is specifically improving VO2 Max (see this comment shared by Derek Ball on Twitter), there is clearly a benefit to caffeine and performance which is worth considering.

HYPOXIA: Adaptations in muscle oxidative capacity, fiber size, and oxygen supply capacity after repeated-sprint training in hypoxia combined with chronic hypoxic exposure

I'm fascinated by altitude training and I love diving into the details of the different protocols. On my resources page you can find lots of studies and different options for altitude and simulated altitude training. This study the authors "adaptations in muscle oxidative capacity, fiber size and oxygen supply capacity in team-sport athletes after six repeated-sprint sessions in normobaric hypoxia or normoxia combined with 14 days of chronic normobaric hypoxic exposure". This is a live-high-train-low-and-high (LHTLH) protocol vs a live-high-train-low (LHTL) protocol. The test protocol included hockey players followed protocols of:

simulated altitude (≥14 h/day at 2,800-3,000 m) and performed regular training plus six repeated-sprint sessions in normobaric hypoxia (3,000 m; LHTLH; n = 6) or normoxia (0 m; LHTL; n = 6) or lived at sea level with regular training only (LLTL; n = 6)

The results showed that:

Our novel findings show that elite team-sport athletes were able to substantially increase the skeletal muscle oxidative capacity in type I and II fibers (+37 and +32%, respectively), while maintaining fiber size after only 14 days of chronic hypoxic residence combined with six repeated-sprint sessions in hypoxia.
This increase in oxidative capacity was superior to groups performing chronic hypoxic residence with repeated sprints in normoxia and residence at sea level with regular training only.

PRACTICAL TAKEAWAY - a LHTLH protocol is more effective than just LHTL or LLTL protocols.

SLEEP: Sleep as a Major Determinant for Mental Health Outcomes in Elite Australian Football League (AFL) Athletes

This study set out "to identify whether sleep and mental health outcomes are associated in elite athletes, and if so, what measures of sleep were the most predictive of mental health outcomes". This is an interesting extension of research into sleep and the mental health in the general population and provides useful insights for athletes.

The results showed that:

Poor sleep predicted 51% of the variation in clinical depression, 42% of the variation in stress, and 31% in clinical anxiety.
Self-reported insomnia symptoms (using the Insomnia Severity Index), were the strongest predictors of poor mental health outcomes, followed by objective sleep monitoring via actigraphy.
Sleep diary measures were the weakest predictors of mental health.

PRACTICAL TAKEAWAY - poor sleep is a major determinant of impaired mental health.

SHOES: Metabolic cost of level, uphill, and downhill running in highly cushioned shoes with carbon-fiber plates

Supershoes are now used by almost all runners top-performing marathon runners. We know that they can offer up to 4% benefit for marathon runners and most marathons are on level ground. "The reduction is attributed to their lightweight, highly compliant, and resilient midsole foam and a midsole-embedded curved carbon fiber plate". In this study the authors set out to determine whether "whether these shoes also reduce the metabolic cost of moderate uphill (+3°) and downhill (–3°) grades".

The authors found:

Compared to the conventional shoes (Streak 6), the metabolic power in the Vaporfly 4% shoes was 3.83% (level), 2.82% (uphill), and 2.70% (downhill) less.
The percent of change in metabolic power for uphill running was less compared to level running but was not statistically different between downhill and level running.
On a running course with uphill and downhill sections, the metabolic savings and hence performance enhancement provided by Vaporfly 4% shoes would likely be slightly less overall, compared to the savings on a perfectly level race course.

PRACTICAL TAKEAWAY - supershoes provide a benefit on moderate uphill and downhill courses too!

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