RESEARCH: Studies reviewed this week: 25 October 2021 to 31 October 2021

TRAINING: LOAD - Effects of Increased Load of Low- Versus High-Intensity Endurance Training on Performance and Physiological Adaptations in Endurance Athletes

This study proposed increasing training load an equal amount using either more low-intensity training, or more high-intensity training. This is interesting as the training load is the same, but the type of training is different and may produce benefits and perhaps elicit greater risks depending on which modality of increased load is selected. The authors found that:

There was no significant difference in performance adaptations between increased load of low- versus high-intensity training in well-trained endurance athletes, although both methods improved performance.

However, a key point about the high-intensity training was that:

Increased load of high-intensity training elicited better maximal oxygen uptake adaptations compared to increased load of low-intensity training.

PRACTICAL TAKEAWAY - low-intensity and high-intensity increases in training load can produce the same performance improvement. However, if you are racing in events that demand more high-intensity efforts and greater VO2Max utilisation, then increased high-intensity may be the best option.

ENVIRONMENT: Effects of Weather Parameters on Endurance Running Performance

"This study evaluated how single or combinations of weather parameters (temperature, humidity, wind speed, solar load) affect peak performance during endurance running events and identify which events are most vulnerable to varying weather conditions". While it is not possible to choose our racing conditions, this type of information can be useful to help guide race plans and to adjust pacing to account for the environmental conditions we face on race day.

The authors researched weather conditions for "1258 races held between 1936 and 2019 across 42 countries, enabling analysis of 7867 athletes" and they found that:

Air temperature (importance score: 40%) was the most important weather parameter.

Conditions of 7.5-15 °C WBGT (or 10-17.5 °C air temperature) increase the likelihood for peak performance.

For every degree WBGT outside these optimum conditions, performance declined by 0.3-0.4%.

PRACTICAL TAKEAWAY - consider the environmental conditions when preparing your race plan and for warmer weather adjust your anticipated performance downwards using 0.3-0.4% for every degree about 15C.

NUTRITION: Accuracy of Flash Glucose Monitoring During Postprandial Rest and Different Walking Conditions in Overweight or Obese Young Adults

A previous study I shared showed that the accuracy of continuous glucose monitors (CGM) is low which impacts their usability for athletes. This study looked at a specific condition of "plasma glucose (PG) measurements during postprandial rest and different walking conditions in overweight/obese young adults". The authors found that:

Although [CGM] readings underestimated PG, the [CGM] accuracy was overall clinically acceptable during postprandial rest and walking in overweight/obese young adults.

PRACTICAL TAKEAWAY - it appears that there are some conditions under which CGM data can be valuable for exercise, however, at this point it appears that in general athletes shouldn't be relying on these devices for glucose measurement.

I recommend also reading this tweet from Bruce Rogers and noting his reservations about the accuracy of these devices. He has extensive experience testing performance measurement devices and I trust his opinion and recommendations.

ENVIRONMENT: Effect of ground technicity on cardio-respiratory and biomechanical parameters in uphill trail running

Guillaume Millet is one of my favorite researchers because he does work that is related to trail and ultramarathon running (and he's an experienced and successful trail runner too). I always enjoy the studies he's associated with because of their practicality and relevance to trail running. In this study the authors' goal was "to analyze the effects of ground technicity on cardio-respiratory and biomechanical responses during uphill running". The testing protocol involved:

Ten experienced male trail-runners ran ∼ 10.5 min at racing pace on two trails with different (high and low) a priori technicity levels. These two runs were replicated (same slope, velocity, and distance) indoor on a motor-driven treadmill. Oxygen uptake, minute ventilation (VE), heart rate as well as step frequency and medio-lateral feet accelerations (i.e. objective indices of uneven terrain running patterns adjustments) were continuously measured throughout all sessions. Rating of perceived exertion (RPE) and perceived technicity were assessed at the end of each bout.

The authors found that:

It is concluded that running uphill on a trail vs. a treadmill significantly elevates both O2Cr and magnitude/variability of feet medio-lateral accelerations but no difference could be identified between trails of different a priori technicities.

These results strengthen the need for trainers and race organizers to consider terrain technicity per se as a challenging cardio-respiratory and biomechanical component in uphill trail running.

PRACTICAL TAKEAWAY - uphill running on a trail is more challenging than running on smooth terrain. Similar to the study above on weather conditions, the type of trails should be considered when preparing a race plan; both the importance of training on technical terrain and the impact on race time should be considered.

PSYCHOLOGY: The effectiveness of pre-performance routines in sports: a meta-analysis

This meta analysis set out to determine the impact of pre-performance routines (PPR) on performance outcomes. The authors define PPRs and distinguish them from superstition as follows:

[PPRs are] "a sequence of task-relevant thoughts and actions which an athlete engages in systematically prior to his or her performance of a specific sport skill" (Moran, 1996, p. 177). Systematic engagement and task-relevance are inherent in this definition to distinguish a PPR from superstitious behaviour (i.e. the behaviour that results from accidental reinforcement of an action so that the person continues to repeat it; https://dictionary. apa.org, n.d.), such as wearing "lucky socks".

The results of the analysis showed that:

A total of 61 separate intervention samples across 15 different sports met all inclusion criteria. These samples yielded 112 effect sizes to analyse. Results showed a significant but small effect of PPRs on sport performance in pre–post designs and moderate-to-large effects in experimental designs, both under low-pressure and pressurised conditions

1. the use of a PPR provides performance advantage – an advantage that can have substantial consequences
2. the PPR intervention proved effective for both female and male athletes, ranging from 11 to 40 years of age, across all skill levels
3. the retrieved studies tested the PPR intervention in 14 different sports, including both individual and team sports, indicating that the intervention can have benefits for a variety of sport tasks
4. our findings can be generalised for both stand-alone and extensive PPRs and across a range of PPR elements (e.g. imagery, quiet eye, left-hand dynamic handgrip)
5. it seems not necessary to individualise the PPR intervention; standardised routines help as well.

PRACTICAL TAKEAWAY - pre-performance routines can improve performance so if you already have one, keep doing it, and if not, considering developing a routine for before you compete.