RESEARCH: studies reviewed this week - 22 June 2020 to 28 June 2020

NUTRITION: The Effect of Acute Caffeine Ingestion on Endurance Performance

Caffeine is well known to improve performance. This recent systematic review investigated the effects of caffeine on endurance performance and found that:

Caffeine has a small but evident effect on endurance performance when taken in moderate doses (3-6 mg/kg) as well as an overall improvement following caffeine compared to placebo in mean power output (3.03 ± 3.07%; effect size = 0.23 ± 0.15) and time-trial completion time (2.22 ± 2.59%; effect size = 0.41 ± 0.2).

Caffeine can be used effectively as an ergogenic aid when taken in moderate doses, such as during sports when a small increase in endurance performance can lead to significant differences in placements as athletes are often separated by small margins.

PRACTICAL TAKE AWAY - caffeine is an ergogenic aid and will improve performance. Recommended dose is 3-6mg/kg of body weight one hour before exercise.

PHYSIOLOGY: Ground Reaction Forces During Downhill and Uphill Running

This study investigated the "ground reaction forces during downhill and uphill running. Our rationale was that these force data would aid in the understanding of hill running injuries and energetics". Most trail runners know that downhill running requires specific preparation and that races with significant descents can have a huge effect on muscle soreness both during and after the event. This study provides some more detail and analysis of why this is:

At -9 degrees, the normal impact force peaks increased by 54%, and the parallel braking force peaks increased by 73%.

Combined with previous biomechanics studies, our normal impact force data suggest that downhill running substantially increases the probability of overuse running injury. Our parallel force data provide insight into past energetic studies, which show that the metabolic cost increases during downhill running at steep angles.

PRACTICAL TAKE AWAY - prepare specifically for races with large descents.

• In early phases of mountain training be cautious on long descents and take walk breaks occassionally.
• Include descents and running at race pace on long downhills when possible in training.
• Work on technique and cadence to reduce the ground contact time and force during downhill running.

PHYSIOLOGY: Thoraco-abdominal Coordination and Performance During Uphill Running at Altitude

This study is quite complex, but provides some useful insights into uphill running technique. The study investigated the "relationships between thoraco-abdominal coordination, ventilatory pattern, oxygen saturation (SpO2), and endurance performance in runners during high-intensity uphill exercise". In any race with steep climbs there are always a wide range of techniques used by athletes from power-hiking to running to using poles, etc. This study found that:

When the slope increased above 30%, the phase angle increased, indicating a reduction in thoraco-abdominal coordination. The reduced thoraco-abdominal coordination was significantly related to reduced breathing efficiency and oxygen saturation (SpO2). Lower SpO2 values were associated with lower speeds at 20%≥slope≤40%.

Reductions in thoraco-abdominal coordination are associated with a less efficient ventilatory pattern and lower SpO2 during uphill running. This fact could have a negative effect on performance.

PRACTICAL TAKE AWAY - bending over significantly during uphill running may reduce performance so it is worthwhile considering uphill technique. Using poles may allow for the runner to keep a more upright posture and choosing not to bend over too much to hike with hands on knees may also help.