RESEARCH: studies reviewed this fortnight - 1 June 2022 to 12 June 2022

CHO: Muscle glycogen storage after different amounts of carbohydrate ingestion

The purpose of this study was to determine whether the rate of muscle glycogen storage could be enhanced during the initial 4-h period postexercise by substantially increasing the amount of the carbohydrate consumed. This is important to consider for post-training recovery and also for stage race nutrition strategies. I've shared a couple of resources on post-exercise nutrition in the past so this builds on some of those topics (glucose vs glucose/fructose; importance of CHO for recovery).

After cycling for 2hrs, the participants consumed either 3g/kg CHO (H), 1.5g/kg CHO (L), and 0g/kg (P). Blood glucose and muscle biopsies were taken at 0, 2 and 4hrs post-exercise. The authors found that:

[Markers] remained below the preexercise concentrations during recovery in the P treatment but increased significantly above the preexercise concentrations during the L and H treatments.
Muscle glycogen storage was significantly increased above the basal rate after ingestion of either glucose polymer supplement.
The rates of muscle glycogen storage, however, were not different between the L and H treatments during the first 2 h or the second 2 h of recovery.

PRACTICAL TAKEAWAY - replensishing glycogen post-exercise is important, but high doses do not appear to increase the rate of restoration.

CHO: What Should I Eat before Exercise? Pre-Exercise Nutrition and the Response to Endurance Exercise

Pre-exercise nutrition is important and I've shared a number of studies in the past that show that being aware of your CHO intake before exercise can impact pacing, athletes do not follow nutrition guidelines, fat oxidation may increase after protein rich breakfast or in a fasted state, sleep-low and train-low CHO strategies may not be as effective as advertised. This review set out "to highlight the current knowledge of the influence of pre-exercise nutrition ingestion on the metabolic, physiological, and performance responses to endurance training".

Some highlights from the paper include:

Acutely, carbohydrate ingestion reduces fat oxidation, but there is little evidence showing enhanced fat burning capacity following long-term fasted-state training.
Performance is improved following pre-exercise carbohydrate ingestion for longer but not shorter duration exercise, while training-induced performance improvements following nutrition strategies that modulate carbohydrate availability vary based on the type of nutrition protocol used.
Contrasting findings related to the influence of acute carbohydrate ingestion on mitochondrial signaling may be related to the amount of carbohydrate consumed and the intensity of exercise.

PRACTICAL TAKEAWAY - in general pre-exercise CHO ingestion will enhance your training performance especially for longer exercise durations.

BREATHING: A Synthesis of Evidence-Based Breathing Strategies to Enhance Human Running

This is a detailed and comprehensive paper of breathing strategies for runners. I highly recommend reading it in full.

A few potential takeaways include:

Several studies report that locomotor-respiratory coupling (LRC) decreases VO2, increases running economy, and reduces dyspnoea.
At lower intensities, we hypothesize that most runners could benefit from slower, deeper, nose breathing, which reduces the risk for respiratory limitations.
The use of resistive breathing devices such as the Training Mask® and POWERbreathe® stress the respiratory system, resulting in positive changes in ventilatory efficiency, muscle recruitment patterns, oxygen delivery, and reduced WOB and dyspnoea.

PRACTICAL TAKEAWAY - rhythmic breathing (LRC) and strengthening the inhalation muscles may be beneficial for performance.

EQUIPMENT: A systematic review of the effectiveness of kinesio taping for musculoskeletal injury

This systematic review examines the evidence for the effectiveness of KT in improving patient outcomes following musculoskeletal injury. The authors found that:

Two of these studies examined musculoskeletal injuries in the lower extremity and reported that the use of KT did not affect outcome measures.
Treatment with KT significantly improved pain levels and range of motion in patients with acute whiplash-associated disorders of the cervical spine both immediately and 24 hours after injury; however, the long-term results did not differ between the 2 groups.
Two studies examined musculoskeletal injuries in the shoulder. The first of these found insufficient evidence to indicate that KT decreases pain and disability in young patients with shoulder impingement/tendinitis, while the second suggested that KT may provide short-term pain relief for patients with shoulder impingement.

PRACTICAL TAKEAWAY - there is "insufficient evidence to support the use of KT following musculoskeletal injury".

CGM: Concurrent Validity of a Continuous Glucose-Monitoring System at Rest and During and Following a High-Intensity Interval Training Session

The studies I've seen in the past suggest that CGM data is not accurate enough for athletes, that there is still work to be done to understand the data from a CGM during an ultramarathon, and that minimally and non-invasive monitoring systems are not sufficiently accurate for detecting hypoglycaemia in routine use. This study set out to "assess the concurrent validity of a continuous blood-glucose-monitoring system (CGM) postbreakfast, preexercise, exercise, and postexercise".

The authors found that:

Overall, mean bias was trivial to small at postbreakfast, preexercise, and postexercise, while moderate during exercise.
A higher median absolute relative difference was observed during exercise (13.6% vs 7%–9.5% for the other conditions).

PRACTICAL TAKEAWAY - "Using CGM to monitor blood glucose concentration during exercise is not recommended. "

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