NUTRITION: The acute effect of fasted exercise on energy intake, energy expenditure, subjective hunger and gastrointestinal hormone release compared to fed exercise in healthy individuals
In this meta analysis the authors est out to determine "the acute effect of fasted and fed exercise on energy intake, energy expenditure, subjective hunger and gastrointestinal hormone release". This information could be useful to help determine the most appropriate way to manage calorie intake while maintaining a calorie deficit to help reduce body mass. The authors found that:
Within-lab energy intake was significantly lower during fasted exercise without a standardised post-exercise meal (FastEx + NoMeal) compared to fed exercise without a standardised post-exercise meal (FedEx + NoMeal). Similarly, 24-h energy intake following FastEx + NoMeal was significantly lower than FedEx + NoMeal.
Energy expenditure was however significantly lower during FastEx + NoMeal compared to FedEx+NoMeal.
This led the authors to conclude that:
FastEx + NoMeal appears to be the most effective strategy to produce a short-term decrease in energy intake, but also results in increased hunger and lowered energy expenditure.
PRACTICAL TAKEAWAY - fasted exercise and no standard post-exercise meal produced the largest calorie deficit (which seems obviously because those participants were eating the least), but it may impact energy expenditure during exercise. This suggests that depending on the type of session and it's goals, and your current calorie management goals, you would need to carefully choose between fasting and not fasting during the session and what type of recovery meal you use.
PHYSIOLOGY: Runners Employ Different Strategies to Cope With Increased Speeds Based on Their Initial Strike Patterns
Footstrike pattern is always an interesting topic because many runners have different opinions on what is optimal and whether it's worth changing or editing this to improve running form. In this study the authors tested the change in footstrike pattern (FSP) at a range of speeds to see if it would change. An important metric they considered was foot strike index (FSI) which shows a rear-foot strike (RFS) at low values and midefoot- or forefoot-strike (MFS) at higher values.
The findings showed that:
The majority of runners (77%) maintained their original FSP by increasing speed. However, we detected a significant (16.8%) decrease in the FSI in the MFS group as a function of running speed, showing changes in the running strategy, despite the absence of a shift from one FSP to another.
However, in the MFS runners we found a significant (16.8%) decrease in the FSI with increasing speeds, which resulted in smaller differences in the FSI between RFS and MFS. This highlights that while the overall FSP did not change, the modification of the FSI within the MFS pattern indicates changes in the running strategy.
There is evidence that the rate of metabolic energy consumption per body weight of running is inversely proportional to contact time. Therefore, the lower decrease of contact time in MFS could affect the energy cost of running.
PRACTICAL TAKEAWAY - footstrike pattern doesn't change much at different speeds, however, the variation in midfoot strike patterns may suggest that these runners have a relatively greater metabolic energy consumption as they speed up.
TRAINING: The effect of high-intensity interval training versus moderate-intensity continuous training on liver fat
This review set out to determine whether high-intensity interval training (HIIT) or moderate-intensity continuous interval training (MICT) would affect liver fat more. This could be a useful study to read in conjunction with last week's study about the impact of different interval types on muscle fibre types.
The authors found that:
Both HIIT and MICT elicited moderate reductions in liver fat % when compared to control. There was no difference between HIIT or MICT.
PRACTICAL TAKEAWAY - for the purposes of liver-fat reduction, both high-intensity and moderate-intensity training are effective.
PHYSIOLOGY: Relationship between respiratory muscle endurance and dyspnea during high-intensity exercise in trained distance runners
This study considered something I haven't thought about before: whether respiratory endurance or strength affects the sensation of breathless more during running. The authors hypothesized that:
The trained distance runners, who have a relatively high respiratory muscle endurance, but not high respiratory muscle strength, have lower dyspneic sensations during submaximal running.
There research tested this hypothesis in runners using incremental respiratory endurance tests (IRET) and maximal inspiratory mouth pressure (PImax) measurements. The results showed that:
The time to endpoint during the IRET was significantly negatively correlated with dyspnea during running at 18 km/h, but not at 16 km/.
There was no significant correlation between PImax and dyspnea during running at 16 km/h or 18 km/h.
PRACTICAL TAKEAWAY - These results suggest that dyspneic sensations during high-intensity running are related to respiratory muscle endurance, but not inspiratory muscle strength, in trained distance runners. This means it doesn't make sense to try and train respiratory strength to improve performance.
TRAINING: The Modifications of Haemoglobin, Erythropoietin Values and Running Performance While Training at Mountain vs. Hilltop vs. Seaside
This is the kind of study I like: a review of three different training camps to see which was the most effective and which environmental factor made the largest difference. The three different training protocols were as follows:
The athletes covered three training periods, as follows: In the first stage, the athletes carried out a training cycle for 21 days at Piatra Arsă, at an altitude of ~2000 m (HIGH). In the second stage, the same group of athletes carried out the same training routine at the seaside, on the Black Sea coast, at Mamaia-Constanța (~0 m) (SAND). Finally, the third training cycle took place in Blaj, at an altitude of ~600 m (CTRL).
The authors tested the athletes for the following measures:
Erythropoietin (EPO) and haemoglobin (Hb) concentration, body weight, VO2max and maximal aerobic velocity (VMA).
The results showed that:
Training during HIGH elicited a greater increase in VO2max and VMA compared with CTRL and SAND. While increases in VO2max and VMA following SAND were greater than those observed after CTRL.
Moreover, EPO increased to a greater extent following HIGH compared with SAND and CTRL with a greater increase following SAND compared with CTRL.
Furthermore, HIGH and SAND elicited a greater increase in Hb compared with CTRL.
This led the authors to conclude that:
While high-altitude training elicited greater relative increases in EPO, VMA, and VO2max, sand training resulted in comparable increases in Hb and may prevent hypoxia-induced weight loss.
PRACTICAL TAKEAWAY - prima facie, this study suggests that there may be some benefit to sand-training that is greater than normal training although not quite as positive as altitude training.
When I shared this on twitter there were a number of responses pointing some issues in the study and also that the benefits of sand training may not be possible to isolate from this work. I recommend that you read the original tweet and the replies to learn more about the topic. Note the the replies are from scientists and coaches that I respect and who have helped me tremendously in the past so they should not just be dismissed without considering their perspectives and knowledge.
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