The Playbook
Biomechanics
The physics of leverage and joint geometry — why the same lift can feel totally different depending on load, body type, and where you are in the range of motion.
Biomechanics — Featured Research
Why Do We Add Resistance Bands When Training?
Your muscles aren’t lifting the weight — they’re acting like hinges on a door. Understanding leverage explains why the bottom of a squat feels like death while the top is easy, why two athletes’ technique can look completely different, and why every lift has a sticking point.
≤20%
Added load sweet spot for bands & chains, relative to total load
Li et al., J Strength Cond Res, 2026 — systematic review & meta-analysis
2026
Meta-analysis: variable resistance beat straight free weights for max strength & jump distance
Li et al., J Strength Cond Res, 2026
Knees → Hips
Power shifts from knee- to hip-dominant as squat load goes from light/fast to heavy/grinding
Farris et al., Scand J Med Sci Sports, 2016
Longest Arm
= greatest torque demand — the exact spot every lift’s sticking point shows up
Lorenzetti et al., J Strength Cond Res, 2012
The Mechanism — It’s a Hinge, Not a Machine
Push a door right next to the hinge and it barely moves. Push it at the handle and it flies open — same door, same you. The difference is leverage, and it determines how your joints and muscles interact with a given load. Scientists put athletes under a barbell, varied the load, and tracked how the mechanics changed: light, fast loads pulled a large share of the power from the knees; heavy, grinding loads shifted it almost entirely to the hips. Same exact movement, two totally different leverage strategies.
At the bottom of a squat, your joints sit at the furthest horizontal distance from the bar’s vertical line of force — the longest moment arm, demanding the most torque your muscles can produce. As you rise, your joints stack back under the bar, the moment arm shrinks, and torque demand drops. Same weight, completely different demand — which is exactly why you never fail at the top.
Coaching Takeaway
Every sticking point — bench off the chest, curl at mid-range, deadlift off the floor — marks the exact position of longest moment arm. It’s never random. It’s geometry.
Long femurs bias the squat toward a forward-lean, hip-dominant pattern. Short femurs bias it toward an upright, quad-dominant pattern — don’t coach two athletes with different anatomy to squat identically.
Bands and chains let you add load specifically where leverage is most favorable, keeping force production high through the entire range instead of just the bottom.
In sports where joint angles mirror the top of a squat, adding resistance to that portion of the range of motion can directly translate to sport-specific power.
Limitations
Leverage explains the strength curve of a given exercise, but mobility determines how much of that range of motion you can actually use — neglect it and you leave power on the table. This does not mean training with only a partial range of motion; mobility and full-ROM strength work are not separate from leverage-based training, they complement it. Resistance bands and the squat are just one illustrative example of a much broader concept that applies across lifts and sports.
References
- Farris DJ, Lichtwark GA, Brown NA, Cresswell AG. Deconstructing the power–resistance relationship for squats: A joint-level analysis. Scand J Med Sci Sports. 2016.
- Lorenzetti S, Gülay T, Stoop M, et al. Comparison of the Angles and Corresponding Moments in the Knee and Hip During Restricted and Unrestricted Squats. J Strength Cond Res. 2012.
- Alves AV, Leicht AS, Deakin GB, et al. Joint-Level Analysis of the Barbell Back Squat During Chain and Elastic Variable Resistance Use. J Strength Cond Res. 2026.
- Li J, Chen Z, Xu K, Wang Y, Gong M. Comparison of Variable Resistance and Free Weight Training on Long-Term and Acute Effects on Different Assessments of Strength: A Systematic Review and Meta-Analysis. J Strength Cond Res. 2026.
- Pallárés JG, Hernández-Belmonte A, Martínez-Cava A, et al. Effects of range of motion on resistance training adaptations: A systematic review and meta-analysis. Scand J Med Sci Sports. 2021.
- Alizadeh S, Daneshjoo A, Zahiri A, et al. Resistance Training Induces Improvements in Range of Motion: A Systematic Review and Meta-Analysis. Sports Med. 2023.
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For educational purposes only — not a substitute for medical advice.