BLUF (Bottom Line Up Front)
This study assessed the mechanical and performance effects of wearing knee wraps during the back squat at 80% 1RM. Results showed increased vertical impulse and peak power output when knee wraps were worn, likely due to the elastic energy stored during the descent and released during the ascent. However, knee wraps also altered movement patterns, reducing barbell displacement and descent duration, and potentially shifting muscular demand away from the hips and toward the knees. These biomechanical changes raise important considerations for how and when knee wraps are used in training.
Purpose of the Study
This study aimed to:
- Investigate whether wearing knee wraps alters mechanical output during the back squat.
- Examine the influence of knee wraps on impulse, peak power, barbell displacement, and movement phase timing.
- Explore how changes in technique may influence training specificity and joint stress.
Subjects
- 10 resistance-trained men
- Mean age: 21.9 ± 2.2 years
- Body mass: 93.3 ± 10.0 kg
- Back squat 1RM: 160.5 ± 18.4 kg
- Average squat experience: 4.4 ± 1.4 years
- All subjects had previous experience using knee wraps, though none used them regularly.
- All were injury-free for ≥6 months before testing.
Research Method
Design
Subjects performed 6 single-rep back squats at 80% 1RM—3 with knee wraps and 3 without. The order was counterbalanced.
Measurements
- Ground reaction force (GRF) and sagittal barbell motion recorded using:
- Dual force plates (500 Hz sampling rate)
- High-speed digital camera (100 Hz) with retroreflective marker
- Variables measured:
- Vertical and horizontal impulse (lowering and lifting phases)
- Peak vertical power
- Horizontal barbell displacement
- Absolute and relative lowering/lifting durations
Knee Wrap Standardization
- Hercules wraps (2.0 m long, elastic cotton)
- Applied using 9 revolutions in a “figure of eight” configuration
- Wrap tension standardized via pre-study pilot testing
Analysis
- Paired t-tests to assess differences
- Effect sizes (ES) classified using Hopkins scale
- ICC values for reliability ranged from 0.93 to 0.99
- Alpha level: p ≤ 0.05
Findings
| Variable | With Wraps | Without Wraps | % Difference | p | Effect Size (ES) |
|---|---|---|---|---|---|
| Vertical Impulse (Lifting) | 192 N·s | 169 N·s | +10% | 0.018 | 1.12 (large) |
| Peak Power | 2,121 W | 1,841 W | +10% | 0.019 | 1.10 (moderate-large) |
| Lowering Duration | 1.13 s | 1.57 s | -45% | 0.006 | 0.82 (moderate-large) |
| Horizontal Displacement (Lowering) | 0.09 m | 0.11 m | -39% | 0.037 | 0.53 (small-moderate) |
| Horizontal Impulse (Lifting) | -263 N·s | -187 N·s | +5% | 0.057 | 0.81 (moderate) |
| Other Variables (e.g., lowering vertical impulse, lifting time) | Not significant | — | — | p > 0.05 | ES small |
Analysis of Results
- Mechanical Advantage: Knee wraps significantly increased vertical impulse and peak power during the lifting phase, indicating a clear mechanical advantage likely due to elastic recoil from the wraps.
- Timing and Movement Pattern: Descent time was reduced by 45%, and horizontal displacement during the lowering phase was significantly reduced. These changes suggest a shift in technique, including a more upright torso and reduced hip joint movement.
- Muscular Emphasis and Technique: The altered movement pattern implies a reduction in hip flexor/extensor involvement and increased knee joint loading. While this may allow heavier loads to be lifted, it changes the muscular demands of the squat and could affect training outcomes.
Conclusion
Knee wraps, when used during back squats at 80% 1RM, enhance vertical force and power output by storing and returning elastic energy. However, these performance benefits come with significant changes in squat mechanics, including faster descent, reduced barbell displacement, and potential redistribution of muscular workload from the posterior chain to the quadriceps and knee extensors. Coaches and athletes should consider these effects when determining the appropriateness of knee wrap use in various training contexts.
Bibliography
Lake, J.P., Carden, P.J.C., & Shorter, K.A. (2012). Wearing knee wraps affects mechanical output and performance characteristics of back squat exercise. Journal of Strength and Conditioning Research, 26(10), 2844–2849.