In a previous study that I shared 100g of additional shoe mass increased 3000m time trial performance by ~1%. In this study the authors test the impact of 50g and 100g of additional shoe mass on running economy (RE) and time to exhaustion (TTE). The authors found that:
HR significantly increased with the addition of mass (50g) at 75% of VT2 and at 75%, 85%, and 95% of VT2 with the addition of 100g.
TTE was significantly longer in the Control condition vs. 100g condition, but not between Control vs. 50g.
PRACTICAL TAKE AWAY - shoe weight is an important factor, but even 50g of additional weight (which is quite a lot per shoe) only affected HR at higher speeds and had no impact on time to exhaustion. I would suggest prioritising comfort and appropriate cushioning over weight for most ultramarathon runners.
TRAINING: Session Rating of Perceived Exertion Combined With Training Volume for Estimating Training Responses in Runners
Measuring training load or training density is import to monitor and guide training presecriptions. The measurement of load needs to consider both the intensity and duration of exercise rather than just the duration. This study set out to "compare week-to-week changes in the training loads of recreational runners using different quantification methods". The authors found that:
The use of an internal training-load measure (sRPE) in combination with external load (training duration) provided a more individualized estimate of week-to-week changes in overall training stress.
PRACTICAL TAKE AWAY - using a measure of training load is preferrable to just looking at duration. There are many options available such as the one in this study (sRPE x duration), TrainingPeaks' TSS, Strava's Relative Exertion, or Polar's TRIMP. Each of them differ slightly so find the one that is most appropriate and most applicable to your training.
TRAINING: Effect of Aerobic Exercise Training and Deconditioning on Oxidative Capacity and Muscle Mitochondrial Enzyme Machinery in Young and Elderly Individuals
It is important for a coach to understand each of their athletes well and to distinguish between the training responses based on each individual. Therefore, studies like this that investigate the difference between training and detraining in young and old runners are useful. Interestingly, the authors found that:
The elderly have a physiological normal ability to improve aerobic capacity and mitochondrial function with aerobic training compared to young individuals.
The elderly had a faster decline in endurance performance and muscle mitochondrial enzyme activity after deconditioning, suggesting an age-related issue in maintaining oxidative metabolism.
PRACTICAL TAKE AWAY - older athletes will gain fitness at similar rates to younger athletes, however, they will lose it much more quicly. Make sure to keep the training of older athletes more consistent with less down-time and shorter off-seasons.
This is a strange study that I never would have thought about and in which I never would have expected the results. This study set out to explore "if exercise-associated intestinal damage was influenced by wearing compression garments, which may improve central blood flow". Using blood samples as a means to measure the impact of a marathon, the authors found that:
The magnitude of increase in postmarathon plasma intestinal fatty acid-binding protein (I-FABP) concentration was significantly greater in control group when compared with runners wearing compression socks.
Wearing compression socks during a marathon run reduced exercise-associated intestinal damage.
PRACTICAL TAKE AWAY - it seems that wearing compression socks may help with gastro-intestinal problems.
A previous study that I shared was a survey of the pre-exercise habits of endurance athletes. This study accompanied that previous study and asked the same survey participants about whether or not they performed fasted endurance training. The results showed that:
The use of fasted training was reported by 62.9% of athletes. The most common reasons for doing so were related to:
- utilizing fat as a fuel source (42.9%)
- gut comfort (35.5%)
- time constraints/convenience (31.4%)
The most common reasons athletes avoided fasted training were that:
- it does not help their training (47.0%)
- performance was worse during fasted training (34.7%)
- greater hunger (34.6%)
PRACTICAL TAKE AWAY - the athletes surveyed either used fasted training because they believed it helped their training, or, they avoided fasted training because they believe it was detrimental to their training. I think that it is more nuanced than that and that fasted training is a valuable modality, but that it needs to be carefully incorporated into a training plan.
NUTRITION: Exogenous Ketosis Impairs 30-min Time-Trial Performance Independent of Bicarbonate Supplementation
I've shared two previous studies on ketones that showed that they do not improve performance (in cyclists, in a 5km running time trial). This study set out to investigated whether "performance also increases if blood ketone levels are increased in the absence of ketoacidosis during high-intensity exercise". The means of reducing ketoacidosis was through co-ingestion of NaHCO3 (bicarbonate). The authors found that:
Neutralization of acid-base disturbance by BIC co-ingestion is insufficient to counteract the slightly negative effect of KE intake during high-intensity exercise.
PRACTICAL TAKE AWAY - it seems that ketones are not a useful fuel source for endurance performance.