RESEARCH: studies shared from 15 to 21 May 23

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:

  1. All the studies I've shared are available on the RESOURCES PAGE.
  2. The weekly summary is distrubted by email through my SUBSTACK NEWSLETTER.


This week's quick summary:

  • Sleep restriction impairs sprint and endurance cycling
  • Three weeks of mental training changes outcomes in time to exhaustion
  • Aerobic HIIT is superior to improve V̇O2 Max compared with SIT
  • Ketone monoester plus carbohydrate supplementation during exercise
  • Impact of cognitive load on running over natural terrain


SLEEP: Sleep restriction between consecutive days of exercise impairs sprint and endurance cycling performance

I have shared multiple studies which show the importance of sleep for athletes. These include a study that showed a negative impact on inflammatory and hormonal responses caused by sleep deprivation, a reduction in mitochondrial function and glucose tolerance caused by sleep restriction, and a negative effect on thermoregulatory defense mechanisms from sleep deprivation. Clearly sleep deprivation should be avoided for all of these reasons. This study adds more direct evidence to show the impact of "sleep restriction (3h) between consecutive days of exercise on sprint and endurance cycling performance, wellness, and mood".

STUDY DETAILS

  1. Participants performed consecutive-day trials with either normal sleep (control) or sleep restriction (3 hours).
  2. Performance measures included peak power tests, time trials, and wellness questionnaires.
  3. Power output was significantly reduced in the sleep restriction group during peak power tests and the 20-minute time trial.
  4. There were no significant differences in heart rate, lactate and glucose levels, or mood states between the control and sleep restriction groups.
  5. Participants reported reduced overall wellness prior to exercise on the second day following sleep restriction.
  6. Sleep restriction and the associated reductions in wellness, reduce cycling performance during consecutive days of exercise in a range of cycling tests that are relevant to both track and road cyclists.

PRACTICAL TAKEAWAY

Sleep deprivation has a negative impact on performance and training. A previous study I shared suggested that only 3% of elite athletes achieve their self-assessed sleep needs. Prioritising sleep is critical for athletes and good hygiene practices are already well established (consistent bed time, a dark and cool room, no electronic devices in the bedroom, etc). The key is to be disciplined and implement these practices. If possible, a 30' to 60' nap at ~2pm would also help.

(Share this on Twitter)



PSYCHOLOGY: Three weeks of mental training changes physiological outcomes during a time trial to exhaustion

Mental training is a valuable aspect of preparing for races (search for "psychology" on my resources page). However, it is not always clear how much mental training is needed and that is where this study could help. The authors set out "to examine the minimum dose of mental training needed to increase performance and elucidate the physiological mechanisms underlying this improvement".

STUDY DETAILS

  1. Participants performed a VO2peak test on day 1 and subsequent time trials to exhaustion (TTE) at 10% above ventilatory threshold (VT) on 6 separate days.
  2. The mental training (MT) group (n=16) watched a 10-15 minute video daily for 3 weeks between visit 3 and 6, while the control group (CON; n=17) did not engage in mental training.
  3. Measurements collected during the time trials included heart rate (HR), rate of perceived exertion (RPE), visual analog scale (VAS) scores for pain and fatigue, electromyography (EMG), and metabolic and neuromuscular data.
  4. The MT group showed a significant increase in TTE starting after 2 weeks (10.0±13.1%) and no further change after 3 weeks (10.4±13.2), while the CON group's TTE significantly decreased during the final trial (-10.3±12.7).
  5. MT led to significant reductions in VO2, ventilation, and breathing frequency during the later stages of the TTE, as well as significantly decreased EMG activity compared to the CON group throughout the trial.
  6. Three weeks of mental training improves performance by reducing EMG, decreasing activation of the muscle and reducing metabolic factors during the latter stages of exercise.

PRACTICAL TAKEAWAY

The benefit of the mental training was significant and therefore something that I'd recommend for athletes to try. A three-week period of mental training was effective so this could be something that athletes focus on in the final phase of their preparation for races. The focus of this intervention was four-fold: breathing exercises to decrease stress and anxiety, "controlling the controllables", self-talk, and imagery to prepare for performance.

(Share this on Twitter)



INTERVALS: Aerobic high-intensity intervals are superior to improve V̇O2max compared with sprint intervals in well-trained men

I recently shared a study that suggested the "minimum work-time during high-intensity aerobic interval training sessions should be at least 1 minute for athletes and 2 minutes for non-athletes". This led to a lot of discussion and one of the longer practical recommendations I've written. This is a fascinating topic and many athletes are interested in how best to perform intervals so this study is more valuable information to add to what we know about intervals. The authors aimed to compare the effects of high-intensity interval training (HIIT) and sprint interval training (SIT) on maximal oxygen uptake (V̇O2 Max), stroke volume, anaerobic capacity, and 3000-meter endurance performance in aerobically well-trained men.

STUDY DETAILS

  1. 48 aerobically well-trained men were randomly assigned to three interval training protocols: high aerobic intensity interval training (HIIT) and two high absolute intensity interval training protocols (sprint interval training; SIT).
  2. HIIT protocol: 4 × 4 minutes at approximately 95% maximal aerobic speed (MAS) with 3 minutes of active breaks.
  3. SIT protocol 1: 8 × 20 seconds at approximately 150% MAS with 10 seconds of passive breaks.
  4. SIT protocol 2: 10 × 30 seconds at approximately 175% MAS with 3.5 minutes of active breaks.
  5. V̇O2max increased more significantly after HIIT (6.5 ± 2.4%) compared to SIT protocol 1 (3.3 ± 2.4%) and SIT protocol 2 (not significant).
  6. HIIT also resulted in a larger increase in stroke volume (O2-pulse) compared to SIT protocol 1 and SIT protocol 2.
  7. Anaerobic capacity increased only after SIT protocol 1, not after HIIT or SIT protocol 2.
  8. Long-distance (3000-m) endurance performance improved in all groups, with HIIT showing a greater improvement compared to SIT protocol 2.
  9. HIIT improves V̇O2max more than SIT. Given the importance of V̇O2max for most endurance performance scenarios, HIIT should typically be the chosen interval format.

PRACTICAL TAKEAWAY

When writing about intervals, I think it's important to include a number of caveats. Many different interval prescriptions can be effective training and different types of intervals can focus on different physiological adaptations. Given that context, my takeaway from this study is that athletes aiming to improve VO2 Max, and who are focusing on a block of specific intervals to try and improve that capacity, should focus on HIIT intervals of ~4' duration. Typical sessions that I recommend for this type of training are intervals of 3' to 5' with equal rest intervals for a total time at intensity of 15' to 20'. The intensity is the maximum intensity an athlete can maintain consistently over all the intervals.

(Share this on Twitter)



SUPPLEMENTS: Ketone monoester plus carbohydrate supplementation does not alter exogenous and plasma glucose oxidation or metabolic clearance rate during exercise in men compared with carbohydrate alone

In the studies I've shared so far on ketones (search for "ketone" on my resources page), I have not been convinced that there is enough evidence that they improve performance. One of the factors that is important in learning more about ketones is to understand how they can be used practically which is where this study comes in. The authors set out "to determine the effect of ketone monoester (KE) plus carbohydrate supplementation on glucose oxidation during steady-state exercise and physical performance compared with carbohydrate alone". This is a test of protocols that are similar to what we hear professional cycling teams are using.

STUDY DETAILS

  1. 12 men participated in the study, consuming either KE+CHO (573 mg KE/kg body mass plus 110 g glucose) or CHO (110 g glucose) before and during 90 minutes of steady-state treadmill exercise.
  2. βHB concentrations were higher in the KE+CHO group after exercise and a time trial compared to the CHO group.
  3. Time to exhaustion (TTE) was lower and time trial performance was slower in the KE+CHO group compared to the CHO group.
  4. Glucose oxidation and metabolic clearance rate were not significantly different between the two groups during exercise.
  5. Glucose rate of appearance and disappearance were lower in the KE+CHO group compared to the CHO group during steady-state exercise.
  6. Rates of exogenous and plasma glucose oxidation and MCR were not different between treatments during steady-state exercise, suggesting blood glucose utilization is similar between KE+CHO and CHO.

PRACTICAL TAKEAWAY

This study suggests that adding ketone monoester to a normal CHO-focused nutrition plan is not beneficial and in fact the intervention appears to decrease performance. My recommendation at this point is that ketones are not beneficial for performance. There is still work to be done to understand ketones better, however, given the cost of these products I would suggest letting others experiment and waiting until the research catches up before trying them.

(Share this on Twitter)



PSYCHOLOGY: Volitional running and tone counting: the impact of cognitive load on running over natural terrain

Mental fatigue can result in reduced paces during time trials and it can negatively impact motor control. This study set out "to examine the impact of cognitive load on volitionally controlled running speed over natural terrain".

STUDY DETAILS

  1. Runners were examined on both even and uneven terrain while performing a dual running and tone-counting working memory task at low and high workloads.
  2. When confronted with increased cognitive load, runners slowed down their running speed. Runners had impaired cognitive task performance only when the cognitive load was high and they were running over uneven terrain.
  3. Counting accuracy significantly decreased during dual task trials only for the high workload task and specifically for the runners on uneven terrain.
  4. A linear trend was observed, indicating that run distance decreased as cognitive load increased for both terrain groups.
  5. Reports of workload, task-focus, and feelings of being spent after running all increased with increased cognitive load regardless of terrain.
  6. The addition of cognitive load to people who have to cover terrain may impair their speed.

PRACTICAL TAKEAWAY

Runners slowed down their speed on technical terrain when dealing with cognitively demanding tasks. Therefore, reducing the cognitive load during a trail race is something that athletes should focus on during their preparation. Some ways to do this are to run on the race trails so the demands of route finding are reduced, developing and practicing a nutrition and hydration plan that does not require extra thought during the event, and trying some orienteering events to practice in technical terrain while performing cognitively demanding map reading.

(Share this on Twitter)

No comments: