Each summary that I prepare adds to my archives and is distributed as a newsletter. If you're interested in either of those you can find them here:
- All the studies I've shared are available on the RESOURCES PAGE.
- The weekly summary is distrubted by email through my SUBSTACK NEWSLETTER.
This week's quick summary:
- Effects of a head-cooling cap on running performance
- Neuromuscular adaptations to short-term downhill running training
- Illness risk factors for athletes preparing for the Olympic Games
- Progressive daily hopping for running economy improvements
- Training adaptations and HRV in elite endurance athletes
HEAT: Effects of a head-cooling cap on 5km running performance in the heat
I have shared a broad range of studies about preparing for hot events (search for "heat" on my resources page). One of those studies looked at wearing a cap and found that there were no positive or negative impacts on thermoregularion and performance. This study looked at a more thorough strategy that involved "continuous head cooling on 5km running time-trial (TT) performance in hot conditions".
STUDY DETAILS
- Ten triathletes (six male, four female) participated in two experimental sessions. Each session involved two 10-minute runs at different intensities, followed by a 5km TT in hot conditions (32.0±0.3 °C, 50.1±1.2% RH).
- Participants were randomly assigned to wear an ice-filled cooling cap or no cooling cap before the 10-minute run at a higher intensity.
- Performance time in the 5km TT was faster when using the cooling cap compared to no cooling cap.
- The cooling cap effectively reduced forehead temperature and increased thermal comfort, providing a more comfortable running experience despite the heat.
- The cooling cap did not significantly affect core temperature, rate of perceived exertion (RPE), fluid loss, blood lactate levels, or heart rate.
PRACTICAL TAKEAWAY
Continuous head cooling with an ice-filled cap has been shown to enhance 5-km TT performance in hot conditions. My recommendation is to use active cooling strategies like this during hot races. This may require having a crew who have ice available at aid stations and is probably easiest with a cap designed to hold ice (I have used this Compressport cap in the past).
DOWNHILL: The time course of different neuromuscular adaptations to short-term downhill running training and their specific relationships with strength gains
The repeated bout effect has shown that athletes can make very quick adaptations to the eccentric demands of downhill running. This study looked at the benefit of short-term downhill running (DR) "to promote strength gains through neuromuscular adaptations".
STUDY DETAILS
- Twelve untrained, young, healthy adults (5 women, 7 men) took part in 4 weeks’ DR, comprising 10 sessions, with running speed equivalent to 60–65% maximal oxygen uptake.
- Isometric and isokinetic knee-extensor maximal voluntary torque (MVT), vastus lateralis (VL) muscle morphology/architecture and neuromuscular activation (VL EMG) were assessed at weeks 0, 2 and 4.
- After four weeks of DR, participants demonstrated an impressive increase in MVT ranging from 9.7% to 15.2%.
- A ~36% increase in vastus lateralis electromyography (EMG) activity during isometric MVT was observed.
- V2max did not show any significant changes after four weeks of DR
- Just 4 weeks’ moderate-intensity DR promoted neuromuscular adaptations in young, healthy adults, typically observed after high-intensity eccentric resistance training.
PRACTICAL TAKEAWAY
The benefits of downhill running on eccentric strength were achieved in just four weeks and ten sessions of relatively short downhills (~15'). My suggestion is to combine this information with the previous work I've shared on the repeated bout effect to come up with an achievable downhill training strategy for athletes who plan to race in mountain ultras. First prize would be the strategy from last week's newsletter, then shorter frequent downhill repeats like this study, and finally eccentric strength training in the gym depending on what terrain and facilities an athlete has available.
PHYSIOLOGY: A multifactorial evaluation of illness risk factors in athletes preparing for the Summer Olympic Games
Missed training of greater than seven days can have a significant impact on race performance, which is why athletes need to be as cautious as possible to avoid any disruptions. This study set out to quantify "the relative contribution of the known medical, behavioural and lifestyle risk factors".
STUDY DETAILS
- The study included 221 Olympic athletes from 11 different sports, who were invited to complete a series of questionnaires nine months prior to the Rio 2016 Olympic Games.
- The questionnaires encompassed a range of factors, including depression, anxiety, stress, resilience, recovery-stress balance, energy levels in females, personal and household hygiene, sleep patterns, probiotic usage, and travel habits.
- Among the 81 athletes who responded (26 male, 55 female), 16 reported illness cases, while the remaining 65 acted as controls. The following associations were observed:
- Female athletes exhibited higher odds of illness
- Low energy availability was significantly associated with illness
- Depression symptoms were linked to an increased risk of illness
- Higher perceived stress levels were also significantly associated with illness
- Low energy availability had high attributable fractions in the population and stands out as a primary association with illness.
PRACTICAL TAKEAWAY
Avoiding illness leading into a race can ensure that an athlete performs at their best. While the different associations in this study are not all easily avoidable or mitigable, low energy availability definitely is. Therefore, leading into important races, athletes should ensure that they are eating enough and focusing on performance as the priority over losing weight or cutting calories.
TRAINING: Progressive daily hopping exercise improves running economy in amateur runners
I have shared studies in the past that show the benefits of plyometric training for runners (study 1, study 2, study 3). This study adds to that research as the authors "investigated the effects of a daily plyometric hopping intervention on running economy (RE) in amateur runners".
STUDY DETAILS
- The study involved a randomized, controlled trial with thirty-four amateur runners, divided into a control group and a hopping exercise group.
- The exercise group engaged in 5 minutes of double-legged hopping exercises daily for a period of six weeks. The intensity of the exercise was gradually increased by manipulating the number of hopping bouts and reducing break duration between sets.
- A significant improvement in RE at running speeds of 12 km/h and 14 km/h was found.
- The exercise did not significantly affect peak oxygen uptake (VO2peak), suggesting that the intervention primarily targeted RE.
- Daily hopping exercise demonstrated its effectiveness in improving RE at higher running speeds for amateur runners.
PRACTICAL TAKEAWAY
A short, simple, hopping protocol improved running economy for athletes. In general, I am cautious about recommending plyometrics because of the potential for injury. However, this protocol is not very demanding as it involves only hopping and no significant bounding or weighted plyometrics so I believe it can be effectively implemented into a training plan. I would suggest performing a phase of hopping exercise (the study was a six-week protocol) at the beginning of the season before moving towards intervals and more focused race-pace training.
HRV: Training adaptation and heart rate variability in elite endurance athletes
I have shared multiple studies on HRV on my resources page ranging from HRV-guided training to the impact of long-distance races on HRV. This paper "addresses the current literature that has assessed changes in HRV in response to training loads" in elite athletes.
STUDY DETAILS
- In elite athletes, the HRV response to training is variable, with longitudinal studies showing no change in fitness (i.e. maximal oxygen uptake [VO2max]) despite an increase in HRV, and other studies showing decreases in HRV despite increases in fitness. As such, there is generally a bell-shaped relationship between vagally-related HRV and fitness.
- The equivocal findings apparent throughout the HRV literature are likely due to the large day-to-day variation in HRV and the variety of HRV indices used for analysis that are more prone to errors.
- It appears that for elite athletes, increases in HRV in the weeks before their event, during their highest training loads, are likely associated with a positive performance outcome.
- It is reasonable to assume that the reduced background of parasympathetic activity/increases in sympathetic activity that occurs during the taper may reflect increased ‘freshness’, and readiness to perform.
- We suggest that longitudinal monitoring is required to understand each athlete’s optimal HRV to R–R interval fingerprint.
PRACTICAL TAKEAWAY
HRV can be a valuable tool for understanding the physiology of athletes which can provide additional insight to guide and modify training. However, understanding each athlete's response to training stimuli is important and developing a "fingerprint" for each athlete is necessary to make the best training decisions. My recommendation is to measure HRV daily and to test the impact of different training stimuli in different physiological states to learn how best to use HRV to assist each individual in their training prescription.
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