RESEARCH: Studies reviewed this week: 19 July 2021 to 25 July 2021

SUPPLEMENT: Iron Metabolism: Interactions with Energy and Carbohydrate Availability

Iron is a critical nutrient for everyone. For endurance athletes, and especially those going to altitude, it is even more important as a nutrient that allows for improved hematological values and therefore great performance. This study investigated the impact of different CHO availabilities on iron metabolism. In particular, the authors "assessed the impact of both acute and chronic carbohydrate (CHO) restriction on iron metabolism, with relevance to contemporary sports nutrition approaches, including models of periodized CHO availability and ketogenic low CHO high fat diets".

The key findings were that:

With regard to CHO availability, acute manipulation of muscle glycogen content, which causes the athlete to “train low”, appears to increase hepcidin levels[this reduces iron availability and absorption] during the recovery from exercise.
Athletes who wish to integrate this specialized training strategy into a periodized training/nutrition program should focus the nutrient manipulation on training sessions that are low in intensity and short in duration to minimize any potential influence on hepcidin concentrations and iron regulation.

PRACTICAL TAKEAWAY - low CHO availability will reduce the absorption of iron from the diet. Therefore be careful at altitude and don't restrict CHO during this phase of training.

HRV: Heart Rate Variability in Psychology: A Review of HRV Indices and an Analysis Tutorial

This paper "aims to provide an overview of the most up-to-date and commonly used HRV indices, as well as common research areas in which these indices have proven to be very useful, particularly in psychology". A few useful notes from the conclusion of the paper are:

Time-domain indices have a long history of usage in HRV research, with RMSSD being arguably the most robust measure of vagal tone.
Although the use of LF/HF has also been quite popular amongst researchers, definitive conclusions about sympathovagal balance based solely on this parameter are ill-advised due to the unclear sources of LF.
Finally, other considerations influence the choice and interpretation of HRV indices, such as recording length, quality of the recorded signal, breathing methods and participant variables (e.g., age, gender, cardio-related medication, etc.).

PRACTICAL TAKEAWAY - this is a useful guide to HRV metrics if you want to understand them better.

EQUIPMENT: The effect of shoe cushioning on injury risk, landing impact forces and spatiotemporal parameters during running

I've shared a few different studies on shoe weight in the past:

In this study the authors tested shoes with different cushioning properties to indentify the impact on injury risk. The key findings were that:

The overall injury risk was lower in runners who had received the shoe version with higher cushioning properties.
In contrast with popular belief, only lighter runners benefitted from higher cushioning.
These results show that the beneficial effect of greater cushioning cannot be explained by a decrease in [Vertical Impact Peak Force] or vertical loading rate.

PRACTICAL TAKEAWAY - cushioning in shoes is a good thing! Don't sacrifice cushioning and comfort for shoe weight.

COACHING: Best-Practice Coaches: An Untapped Resource in Sport-Science Research

The introduction to this paper clearly identifies the role and value of coaches:

An individual’s performance development is regulated by a complex interaction of multiple factors. Our understanding of this interaction is far from complete, something that is likely part of the reason why intuition, experience, and tradition underpin the training and coaching of elite athletes to a greater extent than research-based evidence.

The author goes on to explain the gap between research and coaching. He outlines some vital points that provide a justification for working more closely with coaches in research:

A review of all original investigations and brief reports published in IJSPP from 2015 to 2021 (more than 1100 studies) reveals that coaches have been recruited as participants in less than 0.5% of the cases.
The training science community should therefore strive to describe and verify what the best coaches claim to have known for a long time, and at the same time embrace coaches who have the guts to question research work in their field. This approach provides an effective means of establishing mechanistic connections between training, competitive performance, and underlying physiological determinants.

PRACTICAL TAKEAWAY - optimal performance may come from a combination of good coaching and good sports science. However, there is a gap between these two points and for athletes it is important to find sources that you trust.

FAT & CAFFEINE: Short-Term Influence of Caffeine and Medium-Chain Triglycerides on Ketogenesis

"Bulletproof" coffee which combines coffee with some for of fat (usually butter and MCT) is a popular "hack" for fat loss. This study set out to determine if there is an "increased mobilisation of free fatty acids and release of catabolic hormones by caffeine [that] suggest an influence of caffeine on ketogenesis".

The results showed that:

The interventions with caffeine caused an increase in ßHB levels-in particular, the interventions with C8 highly impacted ketogenesis.
All interventions showed a continuous increase in hunger and diminishing satiety. Mild side effects (total = 12) occurred during the interventions.
The addition of caffeine showed an additive effect on the ketogenic potential of MCT and coconut oil.

PRACTICAL TAKEAWAY - caffeine and MCT increase ketone levels and promote fat metabolism.

ALTITUDE: Psychophysiological Responses to Repeated-Sprint Training in Normobaric Hypoxia and Normoxia

I've shared a wealth of resources on altitude training (see resources page). There are a few researchers whose work I always follow closely: Franck Brocherie, Grégoire P Millet, Olivier Girard. In this paper they investigated "psychophysiological responses to 6 repeated-sprint sessions in normobaric hypoxia (RSH) and normoxia (RSN) in team-sport athletes during a 2-wk "live high-train low" training camp".

The results showed that:

During the 1st session, HR increased across sets independently of the conditions, while SpO2 was globally lower for RSH
Thereafter, SpO2 and HR remained similar across sessions for each condition. While 1st-sprint time remained similar, last-sprint time and fatigue index significantly decreased across sets and sessions.
Despite higher hypoxia-induced physiological and perceptual strain during the 1st session, perceptual responses improved thereafter in RSH so as not to differ from RSN. This indicates an effective acclimation and tolerance to this innovative training.

PRACTICAL TAKEAWAY - athletes can adapt quite quickly to training at altitude and their perceptual responses change in just a few sessions.

No comments: