RESEARCH: Studies reviewed this week: 27 September 2021 to 03 October 2021

NUTRITION: Commercially available carbohydrate drink with menthol fails to improve thermal perception or cycling exercise capacity in males

I've shared a consensus paper in past about the potential benefits of menthol in sports nutrition (available here). This study set out to test the hypothesis that "addition of menthol would improve indicators of thermal perception and improve endurance exercise capacity". The authors found that:

TTE did not differ between both conditions and neither did ratings of perceived thermal comfort or thermal sensation.
Rectal temperature at the end of TTE was comparable between Menthol and Placebo trials.
The present results demonstrate that the addition of menthol to commercially available sports drink does not improve thermal comfort or endurance exercise capacity during ∼65 min of intense virtual cycling.

PRACTICAL TAKEAWAY - there does not appear to be any ergogenic benefit to including menthol in your sports drinks. If you like it, then there's no negative effect to having it in your drink, but it doesn't seem to provide any benefit.

HRV: Season-Long Heart-Rate Variability Tracking Reveals Autonomic Imbalance in American College Football Players

This is a great study that gives us an idea of how heart rate and heart rate variability can change over the course of a season. The author, Andrew Flatt is one of the experts on HRV so it's always useful to see how he's working and to understand the results he's finding. This study showed that:

Relative to preseason, linemen exhibited suppressed LnRMSSD during camp-style preparation for the playoffs, the week of the national semifinal, and the week of the national championship.
For all linemen, RHR trended upward while LnRMSSD trended downward throughout the season.

Leading the author to conclude that:

Attenuated parasympathetic activation is a hallmark of impaired recovery and may contribute to cardiovascular maladaptations reported to occur in linemen following a competitive season. Thus, a descending pattern may serve as an easily identifiable red flag requiring attention from performance and medical staff.

PRACTICAL TAKEAWAY - long-term and season-long HRV trends are important metrics that can help to identify when training needs to be modified or load reduced.

HRV: Healthy Lifestyle and Cardiac Vagal Modulation Over 10 Years

This study looked at the link between healthy lifestyle and HRV. This was conducted over ten years which is a great insight into long-term HRV trends. The details of the study were that:

We prospectively examined associations between a comprehensive measure of 4 important lifestyle factors and vagal modulation, indexed by heart rate variability (HRV) over 10 years. Methods and Results The fifth (1997-1999), seventh (2002-2004), and ninth (2007-2009) phases of the UK Whitehall II cohort were analyzed.

The results showed that:

Compared with participants who reduced their healthy lifestyle scores, those with stable scores displayed higher subsequent high-frequency HRV and higher root mean square of successive differences of normal-to-normal R-R intervals.
Maintaining healthy lifestyles is positively associated with cardiac vagal functioning, and these beneficial adaptations may be lost if not sustained.

PRACTICAL TAKEAWAY - HRV can be a useful indication of vagal function and general health.

NUTRITION: Cocoa Flavanols Improve Vascular Responses to Acute Mental Stress in Young Healthy Adults

The impacts of stress on cardiovascular health are well known and these can measured by HRV as mentioned in some of the studies above. This study investigated the impact of cocoa flavanoals (available as supplements) as a potential way to mediated the impact of stress. The authors found that:

Brachial flow-mediated dilatation (FMD) was impaired 30 min post-stress, yet high-flavanol cocoa attenuated this decline and remained significantly higher compared to low-flavanol cocoa at 90 min post-stress.
High-flavanol cocoa increased Forearm blood flow (FBF) at rest and during stress. Stress-induced cardiovascular and BP responses were similar in both conditions.

This lead the authors to conclude that:

Flavanols are effective at counteracting mental stress-induced endothelial dysfunction and improving peripheral blood flow during stress. These findings suggest the use of flavanol-rich dietary strategies to protect vascular health during stress.

PRACTICAL TAKEAWAY - consider supplementing with cocoa flavanols when you under high levels of mental stress to protect your cardiovascular health.

EQUIPMENT: A Comparison of Running Economy Across Seven Carbon-Plated Racing Shoes

Carbon-plated shoes are prevalent in road races (and they're making appearances in more trail shoes now too) especially on the feet of the top athletes. However, which shoes is best? This study tested seven carbon-plated shoes and one control shoe

  1. Hoka One One – Rocket X (Hoka RX)
  2. Saucony – Endorphin Pro (Saucony EP)
  3. Nike – Air Zoom Alphafly Next% (Nike AF)
  4. Asics – Metaspeed Sky (Asics MS)
  5. Nike – ZoomX Vaporfly Next% 2 (Nike VF2)
  6. New Balance – Fuel Cell RC Elite (New Bal RC)
  7. Brooks – Hyperion Elite 2 (Brook HE2)
  8. Asics – Hyperspeed (Asics HS) -- as a control

The results were that:

RE was improved by 2.7% in the Nike VF2 relative to the traditional shoe in the present study. However, only the Nike AF (3.0%) and Asics MS (2.5%) resulted in similar improvements in RE.
And while other shoes in the lineup did perform statistically better than the traditional (Asics HS) shoe, none resulted in greater than 1.5% improvements on average.

PRACTICAL TAKEAWAY - if you're running a road race you should definitely choose one of these three shoes: Nike Alphafly, Nike Vaporfly 2, Asics Metaspeed Sky.

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