RESEARCH: Studies reviewed this week: 01 November 2021 to 07 November 2021

TRAINING: HRV - The use of heart rate variability monitoring for exercise prescription and performance

I've shared studies in the past about using HRV to guide training. This study wanted to investigate whether or not the same principles could be applied to strength training. This is a useful link as there are multiple studies included under this one overall research topic. The author found that:

We observed that the use of daily HRV to guide high-intensity functional training (HIFT) training resulted in similar cardiovascular, body composition and fitness improvements outcomes with fewer days training at high intensity than predetermined HIFT.
When an individual’s daily HRV was outside their normal variation, decrements in peak power and peak speed were observed during simulated 40-minute cycling time trials.
We show that HRV is an effective tool for the guidance of HIFT, expanding upon the success of HRV to guide aerobic-based training.

PRACTICAL TAKEAWAY - HRV can be used to guide strength training effectively.

NUTRITION: Effects of 30 days of ketogenic diet on body composition, muscle strength, muscle area, metabolism, and performance in semi-professional soccer players

This study investigated the effects of a ketogenic diet (KD) on semi-professional soccer players. The authors wanted to test the impacts on sports performance of following this diet. Over 30 days the players either followed a KD of less than 30g CHO / Day or a convetional Western diet (WD). The results showed that:

There was a significantly higher decrease of body fat, visceral adipose tissue (VAT), waist circumference and extra-cellular water in KD compared to WD group.
Lean soft tissue, quadriceps muscle area, maximal strength and REE showed no changes in both groups.

This led the authors to conclude that:

In our study KD athletes lost fat mass without any detrimental effects on strength, power and muscle mass. When the goal is a rapid weight reduction in such athletes, the use of a KD should be taken into account.

PRACTICAL TAKEAWAY - there are circumstances when a ketogenic diet may be appropriate to achieve weight-loss and fat-mass loss without negatively impacting performance.

NUTRITION: CHO - Overtraining Syndrome (OTS) and Relative Energy Deficiency in Sport (RED-S): Shared Pathways, Symptoms and Complexities

This is such a critical topic that it's worth investigating very thoroughly and the authors involved in this work all have well-respected credentials indicating the importance of their findings. In this narrative review the authors set out to show:

Many of the negative outcomes of training-overload (with, or without an OTS diagnosis) may be primarily due to misdiagnosed under-fueling, or RED-S, via low EA and/or low CHO availability.

The findings based on previous work showed that:

Eighteen of the 21 studies (86%) that met our criteria showed indications of an EA decrease or difference between two cohorts within a given study (n = 14 studies) or CHO availability decrease (n = 4 studies) during the training-overload/OTS period, resulting in both training-overload/OTS and RED-S symptom outcomes compared to control conditions. Furthermore, we demonstrate significantly similar symptom overlaps across much of the OTS (n = 57 studies) and RED-S/Female Athlete Triad (n = 88 studies) literature.
Herein we have demonstrated that OTS and RED-S have many shared pathways, symptoms, and diagnostic complexities.

PRACTICAL TAKEAWAY - overtraining syndrome and RED-S have similar pathways and are both caused by lack of energy availability. Ensure that you are eating enough to fuel the work you're doing otherwise you won't see the adaptations and benefits of all your training (and potentially have even worse outcomes for your health).

Also see this note from Raul Celdran and his experience with overtraining and underfueling.

SLEEP: The effects of evening high-intensity exercise on sleep in healthy adults

Does it matter if you do high-intensity exercise (HIE) before sleep? This systematic review set out "to determine if acute or regular (chronic) HIE performed before bedtime disrupts nighttime sleep of healthy adult, good sleepers compared with a no-exercise control". A useful premise to help us plan our training.

The authors found that:

Acute evening HIE ending 0.5-4 h before bedtime decreased rapid eye movement sleep (-2.34%; p = 0.002) compared with a no-exercise control. No other significant sleep changes occurred.
A regular evening HIE did not disrupt nighttime sleep.
Overall, acute evening HIE performed 2-4 h before bedtime does not disrupt nighttime sleep of healthy, young and middle-aged adults.

PRACTICAL TAKEAWAY - high-intensity exercise close to bed time does not appear to disrupt sleep.

TAPERING: Skeletal Muscle Adaptations and Performance Outcomes Following a Step and Exponential Taper in Strength Athletes

Tapering is well studied in endurance athletes, however, "it is unknown which taper model is most effective for peaking maximal strength and positively augmenting skeletal muscle". The authors of this study worked with powerlifters and compared two taper protocols:

(a) 1-week overreach and 1-week step taper or (b) 1-week overreach and 3-week exponential taper.

The results showed that:

Increases in powerlifting performance following the step and exponential tapers appeared to be mediated by whole muscle, single muscle fiber, and myocellular adaptations.
Specifically, increases in mCSA, fCSA, and MHC-IIA fCSA favored the step taper. Increases in MHC-IIA content with concomitant decreases in MHC-I and -IIX content were also observed following the step taper.

This led the authors to conlude that practically:

Planning an overreach close to competition, followed by a short, step taper may support a more favorable environment to induce fast-twitch fiber adaptations compared to an overreach planned further from competition followed by an exponential taper.
Nonetheless, it is possible that the 1-week step taper did not provide sufficient recovery time for some athletes following the overreach, particularly for deadlift and squat jump performance.

PRACTICAL TAKEAWAY - both tapers worked well, however, there is some nuance in the adaptions that occur and being aware of these is important in which taper protocol you choose. If you are concerned about recovering from the overreach period, then a longer, exponential taper is recommended. If not, a short step-taper may be just as effective.

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