RESEARCH: Studies from 22 to 28 July 24
Sharing research and insights from coaches, scientists and athletes to help us improve endurance performance.
This week’s quick summary:
The night-time sleep and autonomic activity of professional cyclists
The effect of forward postural lean on running economy
Evidence for simultaneous muscle atrophy and hypertrophy
Cognitive impairment during hypoxic acute exposure
Gastric emptying during exercise
SLEEP: The night-time sleep and autonomic activity of male and female professional road cyclists competing in the Tour de France and Tour de France Femmes
Most athletes have experienced different levels of sleep quality that can vary based on the training they did that day. However, it can be challenging to isolate just one factor such as training as the cause of poor sleep. In this study, the authors set out “to test for a main effect of 'stage classification' on various recovery metrics”.
STUDY DETAILS
Participants included 17 professional cyclists (8 males from one team and 9 females from two teams).
The intervention involved wearing a fitness tracker (WHOOP 4.0) to monitor night-time sleep and autonomic activity for the entire event and for seven baseline days before the event.
Measurement methods included total sleep time, sleep efficiency, resting heart rate (HR), and heart rate variability (HRV) during sleep.
Results showed baseline total sleep time was 7.2±0.3h for males and 7.7±0.3h for females, with sleep efficiency of 87.0±4.4% for males and 88.8±2.6% for females.
During the events, total sleep time was 7.2±0.1h for males and 7.5±0.3h for females, with males showing the lowest HRV after mountain stages and females showing the highest percentage of light sleep after mountain stages.
PRACTICAL TAKEAWAY
This study shows that the most demanding stages - mountain stages - had the largest impact on HRV and sleep quality for these athletes. Nevertheless, they appeared to cope quite well with the demands of the race and were typically able to recover before the next stage. My recommendation for athletes is to consider that there may be delayed recovery after a particularly demanding training day and to use this for planning training. It may require another one or two nights of normal sleep to fully recover and be able to perform another hard training day.
RELATED RESEARCH
PHYSIOLOGY: The effect of forward postural lean on running economy, kinematics, and muscle activation
Improving running economy can help improve performance so athletes seek to find these improvements through increased training volume and exercises such as plyometrics. Some runners also receive guidance from their coaches on their form and many runners watch the elites and want to simulate what they are doing. In this study, the authors set out “to evaluate the impact of altering forward postural lean and lean strategy on running economy, kinematics, and muscle activity”.
STUDY DETAILS
Sixteen healthy young adult runners (average age 23, equally split by gender) participated in the study.
Participants ran on a treadmill at 3.58m/s using three lean angles: upright, moderate lean (50% of maximal lean angle), and maximal lean.
Two leaning strategies were tested: lean from the ankle and lean from the waist (trunk lean).
Measurements included metabolic energy consumption, leg kinematics, and muscle activation.
Increased forward postural lean (up to 8±2 degrees) worsened running economy by 8%, increased hip flexion, and heightened gluteus maximus and biceps femoris muscle activation during the stance phase, irrespective of lean strategy.
PRACTICAL TAKEAWAY
The results of this study suggest that to optimise running economy and performance, runners should maintain a more upright or moderate forward postural lean. Excessive forward lean, whether from the ankle or waist, increases metabolic cost and muscle activation, making running less efficient. My recommendation for athletes is be cautious of trying to force a running form such as a forward lean, and rather to settle into the most comfortable running position for them which is most likely more upright.
RELATED RESEARCH
PHYSIOLOGY: Evidence for simultaneous muscle atrophy and hypertrophy in response to resistance training in humans
This study drew me in because of the title which made it sound like it might be possible to gain and lose muscle fibres in the same muscle while strength training. This is not quite the case as the authors were looking at gaining muscle in one area of the body while losing it elsewhere. They set out “to investigate the volume changes in 17 recruited and 13 non-recruited muscles during a 10-week single-joint resistance training (RT) program targeting the upper arm and upper leg musculature”.
STUDY DETAILS
Twenty-one RT novices participated in the study, eating ad libitum with energy and protein intake assessed through self-reported diaries.
Participants underwent a 10-week single-joint RT program focusing on upper arm and upper leg muscles.
Muscle volume changes were measured using manual or automatic 3D segmentation.
Post-training, recruited muscles increased in volume (+2.2% to +17.7%), while non-recruited adductor magnus and soleus muscles decreased (-1.5% and -2.4%, respectively).
Protein intake was positively associated with net muscle growth and changes in adductor magnus volume, while energy intake was positively related to changes in total non-recruited muscle volume.
PRACTICAL TAKEAWAY
The results of this study are consistent with research that shows that resistance training can help preserve lean mass in a period of energy deficiency. However, it appears that only the muscles being used are maintained while non-trained muscles atrophy. This can be used by athletes who want to shift muscle mass on their body to meet the demands of a specific sport or event. My recommendation for athletes who are trying to lose weight or are in a period of energy deficiency perhaps due to high training load, is to ensure that their resistance training meets the demands of their sport and goals so they do not lose critical lean muscle mass.
RELATED RESEARCH
ALTITUDE: Cognitive impairment during combined normobaric vs. hypobaric and normoxic vs. hypoxic acute exposure
This study looks at the impact of acute altitude exposure on pilots. It is also interesting for athletes who may be training at altitude whether simulated or natural. The authors set out “to assess cognitive performance under different pressure and oxygen conditions of acute normobaric hypoxia (NH) and hypobaric hypoxia (HH), as well as hypobaric normoxia (HN)”.
STUDY DETAILS
16 healthy pilot trainees were included in the study.
The intervention involved exposure to four conditions—normobaric normoxia (NN) at 440m, hypobaric hypoxia (HH) at 5500m, normobaric hypoxia (NH) at a simulated 5500m, and hypobaric normoxia (HN).
The duration of the study was acute exposure to the conditions.
Cognitive assessment using the KLT-R test, with cerebral oxygen delivery (cDO2) were estimated via middle cerebral artery blood flow velocity (MCAv) and pulse oxygen saturation (SpO2) during cognitive tests.
Error rates increased significantly in NH (14.3%) and HH (12.9%) compared to NN (6.5%) and HN (6.0%). Calculations accomplished were fewer in HH. Both NH and HH showed decreased cDO2 compared to NN.
PRACTICAL TAKEAWAY
This study highlights that both normobaric and hypobaric hypoxia significantly impair cognitive functions, suggesting the need for effective mitigation strategies in environments where oxygen levels are low, regardless of pressure changes. While athletes are not going to altitudes as high as those used in this study, if they are not acclimated there is a chance that lower altitudes may have similar cognitive impacts. My recommendation for athletes training at altitude training camps or racing in the mountains is to closely follow their race plans and to try and remove any ad hoc decision making while they are exposed to altitude. This can hopefully reduce any errors that may impact the quality of their training or their race results.
RELATED RESEARCH
Variability in hemoglobin mass response to altitude training camps
High intensity and sprint interval training, and work-related cognitive function in adults
Manipulating sleep duration perception changes cognitive performance
HEAT: Gastric emptying during exercise: Effects of heat stress and hypohydration
Racing in the heat is hard and often impacts athletes’ nutrition plans and the effectiveness of achieving these plans. In this study, the authors set out “to determine the effects of various heat and hydration conditions on the gastric emptying rate during exercise”.
STUDY DETAILS
Ten physically fit men participated, ingesting 400ml of water before each of three 15-minute treadmill exercise bouts at approximately 50% VO2 Max on five occasions.
Initial experiments were conducted before heat acclimation in neutral (18°C), hot (49°C), and warm (35°C) environments, with all subjects euhydrated.
Post-acclimation, two additional experiments were performed in the warm (35°C) environment: one while euhydrated and one while hypohydrated (-5% body weight).
Stomach contents were aspirated after each exercise bout to measure the volume of water emptied into the intestines.
Results showed that gastric emptying rate was inversely correlated with rectal temperature (r=-0.76), with significant impairment in hot environments (49°C) and during hypohydration in warm conditions (35°C).
PRACTICAL TAKEAWAY
This study showed that in very hot conditions and in warm conditions when athletes are dehydrated, the gastric emptying rate declines. This means that fueling plans and performance are also likely to decline. My recommendation for athletes in warm conditions is to try their best to stay hydrated during training and racing. For athletes in very hot conditions, they too should try to stay hydrated, but a lowering of the gastric emptying rate is almost inevitable so they should aim to reduce their race intensity appropriately to match the conditions.
RELATED RESEARCH
Quick summary from last week’s paid newsletter
Paid subscribers receive a newsletter every week and have full access to all newsletters listed in the archives (425 studies and practical takeaways). Last week, the newsletter covered studies on the following topics:
Observer effects on the rating of perceived exertion
Effect of paddles on pressure and force generation during front crawl
8-hour time-restricted eating does not lower myofibrillar protein synthesis
Performance and pacing of professional IRONMAN triathletes
Physical exercise and selective autophagy
Thanks, what a great selection of studies - and great summaries and takeaways from each! Very helpful!
I love studies like this and often find so many great topics to write about just from scrolling through titles! The gastric emptying in heat hits hard for me as that is something I suffer greatly with. I lose about two 24 oz. bottles an hour here in Florida in the summer. My sweat rate is very high and that makes it almost impossible to replace what I need. It definitely becomes a challenge in long distance triathlons.