Research Roundup 6.1.23

By Anna Woodring, MTI Strength and Conditioning Coach 


The first study compared running on a treadmill to running outdoors and found that running on a treadmill without any incline is easier due to the absence of air resistance. The researchers found that setting the treadmill at a 1% incline most closely simulates the energy cost of outdoor running for durations over 5 minutes. Less than 1% incline on a treadmill can result in a slower time of 20-30 seconds per mile when compared to outside. 

The second study investigated the impact of wearing external loads during daily activities on the ACFT performance. The study found that wearing a weight vest during daily activities for an average of 16.5 hours per week over three weeks did not improve performance in individual ACFT tasks or the overall ACFT score.

The third study investigated 46 previous studies and found that moderate doses of caffeine (3-6 mg/kg) have a small but discernible positive effect on endurance performance, including improvements in mean power output and time-trial completion time compared to no caffeine. Less than 3 milligrams per kilogram of bodyweight has no effect on endurance performance. 

A 1% treadmill grade most accurately reflects the energetic cost of outdoor running is published in the Journal of Sports Sciences. This study wanted to see how running on a treadmill compares to running outside. Running on a treadmill is easier because there’s no air resistance. The researchers wanted to find out which incline on the treadmill would be most similar to running outside. They had nine experienced male runners participate in the study. The runners ran for six minutes at different speeds, with breaks in between. They did this six times, with five of the runs on the treadmill at different inclines (0%, 0%, 1%, 2%, 3%) and one run outside on a flat road. The researchers measured their oxygen consumption during the last two minutes of each run, and the speeds were set to match outdoor running.

The study discovered that when running at a speed of 5.0 m/s, the energy used during outdoor running was similar to running on a treadmill set at a 1% or 2% incline. Based on the findings, it is suggested that setting a treadmill at a 1% incline can effectively mimic the energy cost of outdoor running for durations longer than 5 minutes.

This study emphasized that simulating outdoor running is most accurately achieved by using a 1% grade on a treadmill. Although I would never advise athletes to choose a treadmill over running outside, there are certain circumstances where it becomes necessary. Considering the impending summer season, running for more than an hour with a pack in cities like Yuma, AZ might pose safety risks. It is important to exercise caution and employ your own discretion. Furthermore, running on a treadmill without any incline (0% grade) generally results in a slower pace, with a potential time difference of 20-30 seconds per mile compared to outdoor running.

Effects Of External Loading During Daily Living On ACFT Performance is published within research conducted at Arkansas State University. This study examined the impact of external loading during activities of daily living (ELDL) on Army Combat Fitness Test (ACFT) performance in 26 male ROTC cadets. Participants were divided into two groups, ELDL and control. The ELDL group underwent a three-week training program with progressive loads of 12%, 15%, and 18% of their lean body mass. Cadets wore the vests an average of 23.18 hours during week 1, 15.32 hours during week 2, and 11.00 hours during week 3.  Vests were not worn during physical training. Physical training for all cadets was identical and consisted of speed training on Monday, Wednesday, and Friday and circuit training on Tuesday and Thursday. Each ACFT task was practiced multiple times throughout the training sessions. After the completion of ELDL, the participants’ ACFT performance was reassessed.

The study’s primary outcome revealed that incorporating a weight vest during daily movement of everyday tasks for an average of 16.5 hours per week over a period of 3 weeks did not lead to any enhancements in either individual ACFT task performance or the overall ACFT score.

It is important to clarify that specialty schools within the DOD may recommend wearing load throughout the day to acclimate the body to the added weight, rather than the focus being on performance improvement. This study did not involve speed work or resistance training in the weighted vest, which could have potentially influenced the results. Simply wearing a weighted vest or pack throughout the day does not lead to improved ACFT scores or running performance. Getting used to carrying a load is necessary, but it won’t improve performance unless trained with. 

The Effect of Acute Caffeine Ingestion on endurance Performance: A Systematic Review and Meta-Analysis is published in the journal of Sports Medicine. Caffeine is commonly used by people in the tactical community to improve their performance. However, there haven’t been recent studies that specifically measure the effects of caffeine on endurance exercise. Elite athletes, especially those in endurance sports, are known to use caffeine as an ergogenic aid, with around 74% of them reportedly using it. Evidence supporting its performance-enhancing effects at doses between 1 and 6 milligrams per kilogram of body weight. Previous studies have mostly used time to exhaustion or time trial protocols to study caffeine’s impact on endurance, with time trials being more relevant to real-life performance. This article focused on analyzing studies that examined time trial performance in practical settings to determine the most effective caffeine dosage.

Results from the meta-analysis of 46 studies showed that moderate doses of caffeine (3–6 mg/kg) have a small yet noticeable positive impact on endurance performance. Additionally, the analysis revealed improvements in mean power output during endurance events and time-trial completion time when comparing to no caffeine. 

Caffeine has a greater impact on endurance performance compared to other fitness elements, although many athletes use it solely for resistance training. It is crucial for athletes to be mindful of their caffeine intake and not exceed 6 milligrams per kilogram of bodyweight. If attempting a high dosage avoid consuming it on test day. Doses below 3mg/kg have shown no performance increase. While the results demonstrate a slight performance improvement, it should be noted that the effect is minimal, likely only reducing run time by 15 seconds or less. 

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