RESEARCH: Studies reviewed this week: 06 December 2021 to 12 December 2021

STRENGTH: Compatibility of Concurrent Aerobic and Strength Training for Skeletal Muscle Size and Function

This review set out to determine "the compatibility of concurrent aerobic and strength training compared with strength training alone, in terms of adaptations in muscle function (maximal and explosive strength) and muscle mass". This is an important question to help athletes design their training week and work on certain components while understanding the impact on other concurrent training modalities.

The authors found that:

Attenuation of explosive strength was more pronounced when concurrent training was performed within the same session than when sessions were separated by at least 3 h.
No significant effects were found for the other moderators, i.e. type of aerobic training (cycling vs. running), frequency of concurrent training, training status (untrained vs. active), and mean age.
Concurrent aerobic and strength training does not compromise muscle hypertrophy and maximal strength development.

PRACTICAL TAKEAWAY - you can do strength and endurance training at the same time without reducing the impact of either.

PSYCHOLOGY: Chronic psychological stress impairs recovery of muscular function and somatic sensations over a 96-hour period

Managing stress is very important for creating the conditions for optimal adaptation to training (see all my articles on HRV here). This study set out to assess "whether chronic mental stress moderates recovery of muscular function and somatic sensations: perceived energy, fatigue, and soreness, in a 4-day period after a bout of strenuous resistance exercise".

The authors found that:

Life event stress significantly moderated linear and squared recovery of maximal isometric force (MIF). This relationship held even when the model was adjusted for fitness, workload, and training experience.
Perceived energy, fatigue, and soreness all were moderated by life stress.
In all analyses, higher stress was associated with worse recovery. Stress, whether assessed as life event stress or perceived stress, moderated the recovery trajectories of muscular function and somatic sensations in a 96-hour period after strenuous resistance exercise.

PRACTICAL TAKEAWAY - if you are experiencing high levels of life stress, it is important to consider this and modify your recovery (increase it) appropriately.

STRENGTH: Effect of concurrent strength and endurance training on run performance and biomechanics

In the study above looking at concurrent strength training and aerobi training they found that it was possible to do both without reducing the benefit of either. In this study they looked specifically at running, investigating "the effect of concurrent strength and endurance (CSE) training on running performance, biomechanics, and muscle activity during overground running". The findings were that the concurrent strength and endurance (CSE) group:

Improved 2-km run time and time to exhaustion during the V̇O2max running test.
Reduced total body fat while total body mass and lean body mass were unchanged.

This led the authors to conclude:

CSE training is beneficial for running performance, but changes in running biomechanics and muscle activity may not be contributing factors to the performance improvement.

PRACTICAL TAKEAWAY - concurrent strength and endurance training is beneficial for runners.

PHYSIOLOGY: Skeletal Muscle Ribosome and Mitochondrial Biogenesis in Response to Different Exercise Training Modalities

Continuing on the investigation into concurrent strength and endurance training, this review ivestigates the important pathways for the adaptation to each of these stimuli and discusses whether or not an interference effect takes place. A few of my highlights are:

Data from multiple studies suggest the existence of a competition between ribosome and mitochondrial biogenesis, in which the first adaptation is prioritized with resistance training while the latter is prioritized with endurance training. In addition, reports have shown an interference effect when both exercise modes are performed concurrently. This prioritization/interference may be due to the interplay between the 5’ AMP-activated protein kinase (AMPK) and mechanistic target of rapamycin complex 1 (mTORC1) signaling cascades and/or the high skeletal muscle energy requirements for the synthesis and maintenance of cellular organelles.

In contrast, the review mentions these two studies suggest there is no competition:

The first study (Fyfe et al., 2016) showed that compared with resistance exercise only, high-intensity interval training and resistance exercise enhanced ACC phosphorylation (Ser79; a readout of AMPK activity), PPARGC1A mRNA expression (suggestive of increased mitochondrial biogenesis), and mTOR phosphorylation [Ser2448; which may indicate enhanced mTOR activity, although this has been debated (Figueiredo et al., 2017)]. The second study by Fyfe et al. (2018) involved three groups of participants who undertook resistance training only, high-intensity interval training + resistance training, or moderate-intensity continuous training + resistance training for 8weeks. Following the training intervention, basal 45S pre-rRNA, 28S rRNA, and 5.8S rRNA expression were greater in the two groups that incorporated high-intensity interval training or moderate-intensity continuous training vs. resistance training alone.

The authors conclude that:

Given the evidence cited in this review, it is pragmatic for individuals who seek to enhance muscle hypertrophy and aerobic capacity to engage in concurrent training.

PRACTICAL TAKEAWAY - concurrent training seems to be ok, and although there is potential for interference there isn't enough evidence to advocate against concurrent training.

SLEEP: The impact of daytime napping on athletic performance

I've shared one study in the past (napping and total sleep time) which suggests that napping is a useful strategy to add to your total sleep hours. This review summarises "the available evidence regarding the influence of napping on exercise and cognitive performance as well as the effects of napping on athletes’ perceptual responses prior to or during exercise".

The authors found that:

Prevailing findings indicate that following a normal sleep night or after a night of sleep loss, a mid-day nap may enhance or restore several exercise and cognitive performance aspects, while concomitantly provide benefits on athletes’ perceptual responses.
Most, but not all, findings suggest that compared to short-term naps (20–30 min), long-term ones (>35–90 min) appear to provide superior benefits to the athletes.

PRACTICAL TAKEAWAY - napping can be beneficial and if you have the time then extend your nap to >35 minutes.

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