Coaches often use the isometric mid-shin pull (MSP) and countermovement jumps (CMJs) to assess and train strength and power.
CMJs can be manipulated using bands (assisted or resisted) or loads (weighted vests), but it's unclear how these changes influence force production and muscle activation.
This study examined the differences in force and EMG characteristics between MSP and four types of CMJs.
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How do changes in CMJ loading (resisted, assisted, or weighted) affect force development and muscle excitation compared to the isometric mid-shin pull?
What Did the Researchers Do?
Conditions Tested
15 resistance-trained adults (12 men, 3 women; ~26 years old, 5+ years of training) were tested under 5 conditions:
- Regular CMJ (bodyweight)
- CMJ with assisted bands (CMJAB, −10% body mass)
- CMJ with resisted bands (CMJRB, +10% body mass)
- CMJ with a weighted vest (CMJV, +10% body mass)
- Isometric Mid-Shin Pull (MSP)
Measurements
- Peak Force (PF)
- Peak Rate of Force Development (PRFD)
- Peak Velocity (PV)
- Peak Power (PP)
- Electromyography (EMG) for vastus lateralis (EMGVL) and vastus medialis (EMGVM)
What Were the Results?
- MSP produced the highest PF across all tests (mean = 2426 N).
- CMJs had higher PRFD than MSP (CMJ: ~20,739 N/s vs. MSP: ~8136 N/s).
- No differences in PRFD across CMJ variations (regular, assisted, resisted, or weighted).
- Peak velocity was higher in CMJ and CMJAB than in CMJRB and CMJV.
- Peak power was highest in CMJ and CMJV.
- Muscle excitation (EMGVL) was higher in all CMJs compared to MSP; no major differences across CMJ types.
- PRFD in MSP was strongly correlated with PP in CMJs (r = 0.68–0.83).
What Does This Mean?
- CMJ is more explosive (higher PRFD) but produces less absolute force than MSP.
- Altering load ±10% via bands or vests didn’t meaningfully improve power output or muscle excitation beyond regular CMJ.
- MSP may be more specific to strength assessment; CMJ better reflects dynamic explosive performance.
- EMGVL activation is significantly higher in dynamic tasks, highlighting their neuromuscular demand.
Coach's Takeaway
- Use MSP to assess max force, not explosiveness.
- Use CMJ to monitor and train power, especially bodyweight jumps.
- Modifying CMJs with bands or vests at 10% of body weight doesn’t offer clear benefits.
Hope this helps.
Ramsey
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