RESEARCH: studies reviewed this week - 26 October 2020 to 01 November 2020

NUTRITION: Nutritional intake and body composition changes in a UCI World Tour cycling team during the Tour of Spain

A fascinating study into what cyclists actually eat during a Grand Tour race. This study measured the cyclists parameters and there were two investigators who weighed and measured all of their food. The researchers found that:

  • Carbohydrate mean consumption of 12.5g/kg/day of body weight (65%).
  • Fat mean consumption of 1.5g/kg/day (18%).
  • Protein mean consumption of 3.3g/kg/day (17%).
  • All micronutrients, except for folate, vitamin D and potassium exceeded the RDA.
  • Generally, this sample of cyclists consumed more protein and less fat than the recommended amount.

PRACTICAL TAKE AWAY - Even with very large quantities of food intake it's possible miss some micronutrients. A careful, personalised diet may be useful in maximising performance.

TRAINING: Refuting the myth of non-response to exercise training: 'non-responders' do respond to higher dose of training

When working iwth athletes it's important to make sure that the training a coach provides is specific to the athlete, to their progress in a training plan, and specific to their race goals. This study looks at the starting point of newer athletes to see how they respond to different training loads. The authors tested the idea that there are some non-responders to cardiovascular exercise and tried to determine ways overcome this:

One in five adults following physical activity guidelines are reported to not demonstrate any improvement in cardiorespiratory fitness (CRF). Herein, we sought to establish whether CRF non-response to exercise training is dose-dependent, using a between- and within-subject study design.
Participants classified as non-responders after the endurance training (ET) intervention completed a successive 6-week ET period including two additional exercise sessions per week.

The results were very informative and showed the need for adding load if there is no response:

In conclusion, individual CRF non-response to exercise training is abolished by increasing the dose of exercise and primarily a function of haematological adaptations in oxygen-carrying capacity.

PRACTICAL TAKE AWAY - if you are not seeing a response or adaptation to your training it may be necessary to increase the stimulus before declaring yourself a non-responder.

PHYSIOLOGY: Changes in Running Economy During a 65-km Ultramarathon

I've mentioned it before, but these are my favorite types of studies even if they are not the most thorough in terms of control. I believe that it's hard to replicate a longer race especially with the terrain and technical variables in a lab so seeing studies looking at runners in ultramarathons are quite informative. I would have assumed that running economy declines during an ultramarathon, but it's useful to have work that backs this up. The authors found that:

The O2 cost, cost of running (Cr), and respiratort exchange rate (RER) increased significantly pre- to post-UM.
This is the first study to demonstrate a consistent increase in O2 cost and Cr among a range of different slopes, at individual running speeds and race-specific slopes giving further evidence that these measures of RE increase in UM running.

PRACTICAL TAKE AWAY - running economy declines during an ultramarathon so training and strategies to decrease the rate of decline could yield good results for improving performance.

PHYSIOLOGY: Exercise-induced muscle damage in humans

This is an older paper that investigated the effects of eccentric exercise on muscle damage. I believe that these effects are well known by now, but it is still valuable to review the authors' work and understand this important aspect of running. The authors found that:

Several indirectly assessed markers of muscle damage after exercise include increases in T2 signal intensity via magnetic resonance imaging techniques, prolonged decreases in force production measured during both voluntary and electrically stimulated contractions, increases in inflammatory markers both within the injured muscle and in the blood, increased appearance of muscle proteins in the blood, and muscular soreness.
Performance of one bout of eccentric exercise induces an adaptation such that the muscle is less vulnerable to a subsequent bout of eccentric exercise. Although several theories have been proposed to explain this "repeated bout effect," including altered motor unit recruitment, an increase in sarcomeres in series, a blunted inflammatory response, and a reduction in stress-susceptible fibers, there is no general agreement as to its cause.

PRACTICAL TAKE AWAY - training for eccentric exercise can reduce it's impact on subsequent exercise through the "repeated bout effect". Prepare for the downhills in a race!

NUTRITION: Natural Vitamin D Content in Animal Products

Vitamin D is mostly derived from the action of sunlight on skin. However, in winter and when wearing sunblock the ability of the body to generate vitamin D is reduced and we need to acquire more through the ingestion of food. This review investigated the vitamin D content of different foods.

  • The highest values of vitamin D are found in fish and especially in fish liver.
  • Offal also provides considerable amounts of vitamin D. The content in muscle meat is generally much lower.
  • Vitamin D concentrations in egg yolks range between the values for meat and offal.
  • If milk and dairy products are not fortified, they are normally low in vitamin D, with the exception of butter because of its high fat content.
However, as recommendations for vitamin D intake have recently been increased considerably, it is difficult to cover the requirements solely by foodstuffs.

PRACTICAL TAKE AWAY - it appears that getting enough vitamin D is very challenging and that it almost certainly needs to be supplemented (see this additional study on optimal vitamin D status).

TRAINING: Physiological Response Differences between Run and Cycle High Intensity Interval Training Program in Recreational Middle Age Female Runners

I have a few athletes who have substituted cycle training for running training due to injury. In that case the fact that they are able to train when they otherwise would not be training is clearly beneficial. However, I have wondered how effective this training is and how much cross-over effect there is (triathletes show that there clearly is some benefit). This study investigate the benefits of either HIIT running or HIIT cycling sessions on female recreational runners and found that:

Maximal oxygen consumption (VO2max) in treadmill running increased significantly after the HIIT run but remained unchanged in HIIT bike.
However, HIITbike improved average velocity in a 10 km running time trial (TTrun).
A regime of HIIT in cycling may evoke increases in female recreational runners' power, which may be related with improvements in a 10 km TTrun independent of changes in aerobic capacity.

PRACTICAL TAKE AWAY - there may be valuable substitution effects for HIIT cycling sessions for runners who cannot perform their HIIT running sessions.

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