RESEARCH: Studies reviewed this week: 9 November 2020 to 15 November 2020

SLEEP: The effect of sleep restriction, with or without high‐intensity interval exercise, on myofibrillar protein synthesis in healthy young men

I've shared a few papers in the past about detraining which often seens decreased rates of myofibrillar protein synthesis. In this study the authors investigated the effects of sleep restriction and interval training on myofibrillar protein synthesis (MyoPS). They found that:

Participants undergoing a sleep restriction protocol (five nights, with 4 h in bed each night) had lower rates of skeletal muscle MyoPS.

Rates of MyoPS were maintained at control levels by performing HIIE [cycle intervals of 10 x 60"/75"] during the period of sleep reduction.

This led the authors to conclude that:

Our observation that those participants performing HIIE during the SR intervention were able to maintain their rates of MyoPS at levels comparable to the NS group could have important implications for a range of populations experiencing inadequate sleep and lends support to the idea that HIIE could be a viable intervention to mitigate certain detrimental effects associated with sleep loss.

PRACTICAL TAKE AWAY - sleep restriction has a negative impact on protein synthesis and associated impacts on performance. Try not to go through periods of sleep restriction, but if you do then HIIE can help to mitigate the impact of sleep restriction.

DOWNHILLS: Exercise-induced muscle damage and potential mechanisms for the repeated bout effect

In previous papers on downhill running (effects of downhill running, exercise induced muscle damage) the authors have concluded that the best way to prepare for downhills is through running downhills. The "repeated bout" effect allows us to become used to the descents and lowers the impact of future descents.

In this paper the authors propose that the mechanisms of repeated bout effect are:

It is possible that the repeated bout effect occurs through the interaction of various neural, connective tissue and cellular factors that are dependent on the particulars of the eccentric exercise bout and the specific muscle groups involved.

PRACTICAL TAKE AWAY - make sure to include downhill training at race pace in your training plan to create all the adaptions from the repeated bout effect.

NUTRITION: Comparable Exogenous Carbohydrate Oxidation from Lactose or Sucrose during Exercise

I've seen ultramarathon runners using yoghurt and other dairy products as fuel (usually in European and in aid stations). I've always wondered how beneficial this is and whether it is a good source of nutrition mostly because in the past I have avoided dairy in the days leading to a race and during a race too. However, in this study the authors showed that:

Lactose and sucrose exhibited similar exogenous CHO oxidation rates during exercise at moderate ingestion rates. Compared with sucrose ingestion, lactose resulted in higher fat and lower endogenous CHO oxidation.

PRACTICAL TAKE AWAY - lactose can be an effective source of fueling for endurance activity [note the low intensity of the trial though].

NUTRITION: Impaired Cardiac Autonomic Functions in Apparently Healthy Subjects with Vitamin D Deficiency

Vitamin D deficiency is quite common among the general population and especially in the northern hemisphere over the winter months. I've tested low for vitamin D in the past despite spending considerable time outdoors in the sunlight so I find this topic quite interesting and relevant. This study set out to "assess the cardiac autonomic functions by using heart rate recovery index (HRRI) and heart rate variability (HRV) in apparently healthy subjects with VitD deficiency". The authors found that:

Cardiac autonomic functions are impaired in patients with VitD deficiency despite the absence of overt cardiac involvement and symptoms.

PRACTICAL TAKE AWAY - make sure that you're getting enough vitamin D (here are notes on the vitamin D content of food).

NUTRITION: Cardiac autonomic dysfunctions are recovered with vitamin D replacement in apparently healthy individuals with vitamin D deficiency

Following on from the previous study above, you may be wondering how easy it is to recover from low vitamin D levels or a deficiency. This study "aimed to evaluate the impact of VitD replacement on cardiac autonomic dysfunction". The authors found that:

Cardiac autonomic dysfunction improved after VitD replacement [VitD deficiency group received 300,000 IU vitamin D3 at once, per oral] in otherwise apparently healthy individuals.

PRACTICAL TAKE AWAY - if you are vitamin D deficient it is possible to recover you cardiac autonomic function through replacement strategies.

NUTRITION: Achieving energy balance with a high‐fat meal does not enhance skeletal muscle adaptation and impairs glycaemic response in a sleep‐low training model

Training low has been shown to help improve performance in endurance athletes (my notes from a previous study here). How exactly to go about this process provides a number of different options to an athlete. This study investigated whether or not "achieving energy balance mainly with ingested fat in a ‘sleep‐low’ model of training with low muscle glycogen affect the early training adaptive response during recovery. The protocol followed in the study was:

  • On day 1 they cycled to deplete muscle glycogen while reaching a set energy expenditure (30 kcal (kg of fat free mass (FFM))−1).
  • Post‐exercise, low carbohydrate, protein‐matched meals completely (EB‐HF, 30 kcal (kg FFM)−1) or partially (ED‐LF, 9 kcal (kg FFM)−1) replaced the energy expended, with the majority of energy derived from fat in EB‐HF.
  • In the morning of day 2, participants exercised fasted, and skeletal muscle and blood samples were collected and a carbohydrate–protein drink was ingested at 0.5 h recovery.

The authors found that:

Replenishing energy after glycogen‐depleting exercise with a low‐carbohydrate high‐fat meal in a ‘sleep‐low’ model does not enhance skeletal muscle adaptation and metabolic response in comparison to a low‐carbohydrate low‐fat (low energy) meal.

PRACTICAL TAKE AWAY - trying to replace energy using a high-fat meal while maintaining low levels of glycogen does not provide any benefit over a low-energy meal.

No comments: