RESEARCH: Studies shared from 30 Jan to 5 Feb 23

All the studies I've shared are available on the RESOURCES PAGE.

This week's quick summary:

• RPE: revisiting the history and practical applications
• The cost of training disruptions on marathon performance
• Effects of dehydration on cognitive performance and mood
• Napping to improve cognitive and physical performance
• Nutrition of male adolescent runners in Kenya

TRAINING: Perceived Exertion: revisiting the history and updating the neurophysiology and the practical applications

Rating of perceived exertion (RPE) is a metric that has been around for a long time (a review of 25 years of using RPE) and it is simple, free and easy to use. It doesn't appear to matter much whether the Borg (6-20) scale of the CR10 (1-10) scale are used although there may be some benefit for a CR100 scale in research (see this note from Jeff Rothschild). In this paper the authors "discuss a contemporary definition that considers perceived exertion as a conscious perception of how hard, heavy, and strenuous the exercise is, according to the sense of effort to command the limbs and the feeling of heavy breathing (respiratory effort)".

STUDY DETAILS

1. The afferent feedback theory, holds that sensory brain areas produce the perceived exertion proportionally to mechanical and metabolic signals detected by receptors in the skeletal muscles and cardiorespiratory system.
2. The corollary discharges theory proposes that the signals that generate the perceived exertion come from efferent copies associated with motor command to locomotor muscles and the central drive to respiratory muscle.
3. Maximal oxygen uptake and peak exercise intensity are frequently used to assess cardiorespiratory fitness and individualize exercise prescription, respectively.
4. Monitoring athletes’ responses to training (i.e., training effect) can provide valuable information to refine the training process, maximizing the chances of improving sports performance and minimizing the risk of injury, illness, nonfunctional overreaching, or overtraining.
5. It is possible to use the perceived exertion corresponding to percentages of maximal oxygen uptake or maximal heart rate obtained in incremental testing (e.g., 60% and 80%) to control exercise intensity during training sessions.
6. We strongly recommend using the original scales versions, regardless of whether it is Borg’s scales or not, since the psychophysics properties of the RPE and CR10 scales (and others) were carefully verified and validated over several research years.

PRACTICAL TAKEAWAY

RPE is a valuable metric for measuring exertion and despite advances in other areas of sports science, the original RPE scales are still valuable and useful for athletes and coaches. Many coaches prefer a CR10 scale (ranging from 1 to 10) as this is often more intuitive for athletes and this is what I would recommend for measuring RPE.

TRAINING: Estimating the cost of training disruptions on marathon performance

STUDY DETAILS

1. This study aims to investigate the frequency and performance cost of training disruptions, especially among recreational runners.
2. We identified periods of varying durations up to 16 weeks before the marathon where runners experienced a complete cessation of training (so-called training disruptions).
3. We identified runners who had completed multiple marathons including: (i) at least one disrupted marathon with a long training disruption of >7 days; and (ii) at least one undisrupted marathon with no training disruptions.
4. Over 50% of runners experienced short training disruptions up to and including 6 days, but longer disruptions were found to be increasingly less frequent among those who made it to race-day.
5. Runners who experience longer training disruptions (>7 days) suffer a finish-time cost of 5–8% compared to when the same runners experienced only short training disruptions (<7 days).
6. Faster runners also experience a greater finish-time cost (5.4%) than slower runners (2.6%).
7. And, when disruptions occur late in training (close to race-day), they are associated with a greater finish-time cost (5.2%) than similar disruptions occurring earlier in training (4.4%).

PRACTICAL TAKEAWAY

Missing >7 days of training during a marathon build will definitely have a significant impact on performance (and more for faster runners and when closer to the race). If possible, avoid these types of disruptions in training. This could mean shifting to a "maintenance" mode of training of 50-60% or normal training volume and maybe including a few strides if possible. If an athlete is injured and the period extends beyond 7 days without training, then they need to re-adjust race expectations or consider choosing another race later in the season.

HYDRATION: Effects of dehydration and rehydration on cognitive performance

A previous study I shared showed that dehydration of up to 3% did not affect performance. I also shared an extensive review that suggested there may be some decrease in performance when dehydrated which also included challenges, research, options, and methods for hydrating. I found this study interesting because it was looking at cognitive performance and the impact on mood of dehydration which are indirectly linked to endurance performance (especially during longer races).

STUDY DETAILS

1. After 12 h of overnight fasting, the participants took baseline tests. First morning urine and blood osmolality were analyzed. Height, weight, and blood pressure were measured. A visual analog scale for the subjective sensation of thirst was applied. Tests were conducted for cognitive performance.
2. Participants were required not to drink water for 36 h but were given three meals on day 3.
3. On day 4, the same indexes were tested as a baseline test.
4. 30' later participants drank 1500 mL of purified water over 15 min. After a 1 h interval, the same measurements were performed.
5. Compared with baseline test results, during the dehydration test, participants had lower scores of vigor and esteem-related affect, lower total scores of digit span, and higher error rates for dose-work.
6. Compared with the dehydration test scores, rehydration test scores showed that fatigue and total mood disturbance (TMD) improved, and scores of forward, backward, and total digit span increased.

PRACTICAL TAKEAWAY

Dehydration negatively impacts cognitive performance and mood. During an ultra-marathon this could have an impact on performance. Therefore try to avoid dehydration during long races; and, if dehydrated it may be worth taking time in an aid station to rehydrate especially before challenging or technical sections of a race.

SLEEP: Is daytime napping an effective strategy to improve sport-related cognitive and physical performance and reduce fatigue?

Daytime napping can supplement night-time sleep and it appears that longer naps provide more benefit for athletes. This meta analysis looked to "estimate the association between daytime napping and cognitive and physical sport performance and fatigue after normal sleep and partial sleep deprivation".

STUDY DETAILS

1. In the 22 included trials, 291 male participants (164 trained athletes and 127 physically active adults) aged between 18 and 35 years were studied.
2. When performed after a normal night of sleep, napping from 12:30 hours to 16:50 hours (with 14:00 hours being the most frequent time) improved cognitive and physical performance and reduced the perception of fatigue.
3. The positive effects of napping were also confirmed after partial sleep deprivation.
4. Overall, the benefits were higher with a nap duration between 30 and <60 min and when the time from nap awakening to test was greater than 1 hour.

PRACTICAL TAKEAWAY

Napping is beneficial for cognitive and physical performance. The study suggests that between 30' and 60' at ~14h00 is optimal.

NUTRITION: Food and macronutrient intake of male adolescent Kalenjin runners in Kenya

STUDY DETAILS

1. A nutritional survey based on twelve adolescent male Kalenjin runners in Kenya during a 2-week field study was carried out in order to determine the composition of their diet and make a comparison with macronutrient recommendations for athletes.
2. The diet of the Kalenjin runners was very high in carbohydrate (71 % 8.7 g/kg body weight per d) and very low in fat (15 %).
3. Intake of total protein (13 %; 1.6 g/kg body weight per d) was above the daily intake recommended by the Food and Agriculture Organization/World Health Organization/United Nations University.
4. The energy intake was mainly derived from vegetable sources (90 %) with maize and kidney beans as the staple food (81 %).
5. The diet of the Kalenjin runners met recommendations for endurance athletes for total protein and most essential amino acid intake as well as carbohydrate intake even though it was based on a small range of food items.

PRACTICAL TAKEAWAY

The adolescent Kalenji runners in this study ate a high carbohydrate diet at 71% of daily calories. These were the top performing runners in their region and their training was ~1hr per day on average. A high carbohydrate diet appeared optimal to support their endurance training.