Mini Study: Run Time Correlates to Ruck Speed Much Better than Relative Strength

By Rob Shaul


This Mini Study tested the correlation between (1) relative strength and ruck speed, and; (2) 6-mile run time and ruck speed with the aim of identifying which (relative strength or running performance) had the highest correlation.

The results found that both 6-mile run time had a high correlation to rucking speed and relative strength, a small correlation.

These results suggest a greater emphasis on running over strength programming for ruck-focused training programs.



Rucking, or extended movement under load, is a physical activity mode which extends across all of the athletes MTI works with: Military, Mountain, Law Enforcement and Fire Rescue. Correspondingly, we have conducted multiple ruck-focused research. Below are examples of previous studies:

A 2015 Mini Study found that for men, bodyweight and 2-mile run time were the best predictors of a 10K ruck effort carrying 60+ pounds.

This study piggy backed and updated that previous effort by testing the predictive value (correlation) of relative strength (strength per bodyweight) and 6-mile run time, to a 3-Mile ruck effort carrying 45#.

Twelve veteran MTI lab rats and athletes, over a course of 5 days, completed three assessments: (1) MTI Relative Strength Assessment;  (2) 3-Mile Ruck for Time @ 45#; (3) 6-Mile Ruck for Time.

The MTI Relative Strength Assessment is a 4-event strength assessment of strength per bodyweight. The events are 1RM (1 repetition maximum) Front Squat, 1RM Bench Press, 1RM Hinge Lift and max rep bodyweight pull ups.

Below was the testing schedule:

Post assessments, a simple correlation was performed.

MTI research is primarily focused on improving MTI programming. This study pitted Relative Strength vs. 6-Mile Run time as a predictor of rucking performance. If one stood out over the other, the results could influence the training time allocated to each in our many programs designed to prepare athletes for ruck-focused selections, events, courses and fitness assessments.



Below are the mini-study results:

The 6-Mile Run Time (.896) was found to have high positive correlations to 3-mile rucking speed. Fast runners are also fast ruckers.

Relative Strength (.231) was found to have a small correlation with rucking speed.

Below are the Lab Rat’s raw scores.

In terms of the relative strength assessment, here is how the overall scoring ranks:

Statistics aside, of the twelve Lab Rats, seven had a sub 10-min/mile ruck time, and a sub 8 min/mile, 6-mile run time: Rob L, Chris K, Charles, Amy, Derek, Anna and Ellie. This seems to back up the statistical results linking run performance with ruck performance:

However, five of the 12 lab rats scored “excellent” on the MTI Relative Strength Assessment, and also completed the ruck under 30 minutes … so I’m somewhat puzzled by the big discrepancy in correlation results.

One element of this study which perhaps skewed the results are the high levels of fitness of the lab rats. Scoring “excellent” on MTI’s relative strength assessment, while also being able to run a sub 8 min/mile, 6 mile effort is no joke. I suspect conducting this study with less fit lab rats might yield different results.

However, the study does seem to indicate that in terms of programming, unloaded running speed and endurance has a greater “bang for your buck” transfer to rucking performance than strength training.


MTI’s current military selection and base fitness programming has been proven to be successful for many athletes facing ruck-based selection events and I’m hesitant to make significant changes without some more study.

One benefit of high relative strength not tested in this study is it’s impact on durability. We’ve found that stronger athletes are harder to injure, when they do get injured, don’t get injured as bad, and overall, recover faster.

Given that, our next step is to re-do this mini-study with regular, line-unit, military athletes.


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