Mini Study: Chassis Integrity Assessment Needs Refinement

BLUF (Bottom Line Up Front)

Four MTI athletes tested a new Chassis Integrity assessment format over a 5-week cycle. The test included movements targeting flexion (Sandbag Sit-Ups), extension (Good Mornings), rotation (Sandbag Keg Lifts), and isometric tension (Elevated Weighted Bridge Holds). Improvements were made across all domains in the individual movements.

However, the assessment’s complexity revealed issues: excessive duration, inconsistent loading, and variability in movement standards. These factors necessitate a shift toward a more concise, operationally-relevant format.

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Background

Chassis Integrity refers to the strength and durability of the midsection—serving as a functional bridge between upper and lower body performance under tactical and mountain load.

While MTI programming has emphasized this concept for years, no singular, validated assessment existed. This Geek Cycle aimed to build and validate one, combining representative movements across:

• Flexion: Sandbag Sit-Ups

• Extension: Barbell Good Mornings (95#)

• Rotation: Sandbag Keg Lifts

• Isometric: Elevated Weighted Bridge Hold for time

All elements were trained twice weekly using fixed volume progressions. Loads were increased after the initial assessment if reps exceeded a certain threshold, then kept the same throughout the cycle.

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Study Design

Participants:
Sam, Jackson, Emmett, Seung

Initial Assessment:

• Max rep Sandbag Sit-Ups in 90 seconds

• Max rep Good Mornings in 90 seconds

• Max Elevated Weighted Bridge Hold

• Max rep Sandbag Keg Lifts in 90 seconds

Progression 
2x/week – 5 Rounds Every 2 Minutes:

• 30% (1 session)

• 35% (2 sessions)

Mid-Cycle Assessment

Progression 
2x/week – 5 Rounds Every 2 Minutes:

• 40% (1 session)

• 45% (2 sessions)

Final Assessment

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Results

All athletes showed improvement in all four exercises from the initial to the final assessment. Extension (Good Mornings) showed the most significant percentage gains, particularly for Jackson (+157.7%), Emmett (+127.7%), and Sam (+70.8%). Seung notably also improved his Good Mornings, however a comparably lower percentage (17.9%). Keg Lift and Sit-Up numbers improved consistently across the board after loads were adjusted upward from 60 to 80 pounds based on early performance. Bridge Hold times also increased for every athlete except Sam, who returned to near his initial time after a mid-cycle dip.

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Discussion

While athletes were able to significantly improve in all areas, the assessment format itself revealed major limitations. The full test took over an hour to complete due to setup requirements, uncertainty about proper weights, and the need to standardize range of motion—particularly for the Good Mornings. Emmett required additional stretching to reach full range, and plate placement during the Elevated Bridge made the test logistically challenging. In some cases, athletes needed help just to place the plate on their back, and position could affect the difficulty (higher placement made the hold easier).

The 90-second rep format created problems across all exercises. The tests turned into speed-based sprints rather than strength or strength endurance assessments. Chassis Integrity as a concept blends both strength and strength endurance. A 1RM approach doesn’t work, but 90 seconds may be too short to fully assess strength endurance either. Most of MTI’s existing Chassis Integrity circuits last 15–30 minutes. These shorter assessments felt more like work capacity efforts—lacking the sustained stress or max-loading challenge typical of Chassis Integrity training.

Good Mornings also raised concern about test validity. Sam completed 82 reps at 95 pounds, raising questions about whether the test measured strength, strength endurance, or just capacity for rapid movement. The same could be said for the Keg Lifts, which began to tax grip and lungs more than core. Sit-Ups also became more about speed than actual flexion capacity.

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Next Steps

This cycle confirmed that while the current model can build Chassis Integrity, it’s not a viable assessment tool in its current form.

Moving forward, we plan to test a simplified AMRAP-based format: a 10-minute Sandbag Get-Up (SBGU) assessment. This single movement integrates flexion, extension, rotation, and isometric tension under load—and includes a strength endurance component. We’ll retest athletes from this study to examine carryover.

The goal is to create a scalable, logistically simple, and functionally complete Chassis Integrity assessment—one that effectively reflects MTI’s broader programming goals.