Unit 4 – Variables in Power & Plyometric Training

Key Terminology & Overarching Goals

  • Power training goal
    • Improve Rate of Force Development (RFD) / rate of force production.
    • Achieved by simultaneously increasing force and velocity.
    • Governing equation: Power=Force×VelocityPower = Force \times Velocity.
  • Plyometric training goal
    • Minimize amortization phase (time between eccentric → concentric actions).
    • Enhance neuromuscular efficiency when transitioning from deceleration to acceleration.

Exercise Selection

  • Always align selection with:
    • Specific patient / client goals (tasks, sports, ADLs).
    • Physiological goal (↑ force, ↑ velocity, ↓ amortization).
  • Common resistance modes
    • Mechanical: dumbbells, barbells, medicine balls.
    • Body-weight or un-weighting (to prioritize velocity).
  • Creativity is encouraged but every choice must have a defensible rationale.

Exercise Order (Sequencing)

  • Guiding principle: Fatigue accumulates → exercises placed earlier yield better adaptation/hypertrophy.
  • Frequent rationales for ordering
    • Power movements first → maximal velocity possible while fresh.
    • Large → small muscle groups (safety; technical complexity while unfatigued).
    • Power at session end only if deliberately assessing power under fatigue.
  • Take-home: There is no universally ​“right” order; have a reason and be able to articulate it.

FITT Parameters for Power (ACSM & Morrison et al.)

  • Intensity: “Maximal” effort yet low RPE (short bouts prevent global fatigue).
  • Duration / Reps: 3–6 s3 \text{–} 6\,\text{s} (≈ 3–6 reps).
  • Sets: Low (1–3 typical for a given movement).
  • Rest: 1–2 min1 \text{–} 2\,\text{min} between sets (≈ full ATP-PCr recovery).
  • Untrained / Older adults
    • Still cue high velocity but possibly phrase as “quickly” vs “as fast as you can”.
    • Emphasize major muscle groups; heightened attention to safety & cueing.

Contraction Type & Tempo

  • Eccentric phase ≤ 4 s → facilitates peak velocity.
  • Eccentric ≥ 6 s → ↓ peak velocity.
    • Mechanisms: Loss of stored elastic energy as heat; ↓ neuromuscular receptor excitability.
  • Quick eccentric + short amortization ⇒ larger concentric force via elastic energy recoil.
  • Caveat: Extremely small ROM lowers absolute force potential (must balance ROM vs speed).
Muscle–Tendon Length–Tension Interaction
  • Muscle force highest at mid-range lengths (optimal actin–myosin overlap).
  • Tendons store more elastic energy as they lengthen → contribute to force if recoil is rapid.
  • Practical design: Choose ROM that places muscle near mid-length and allows swift stretch-shorten cycle.

Load–Velocity–Power Relationships

  • Force–velocity curve: ↑ external load → ↓ movement velocity (inverse relationship).
  • Peak power typically at ~30%30\% 1-RM ("light-moderate" load executed at maximal speed).
  • Rate of Force Development (RFD)
    • RFD=ΔForceΔTimeRFD = \frac{\Delta Force}{\Delta Time}
    • Highest slope reached with moderate force + maximal velocity (~<½ max force).
Integrating Heavy & Explosive Training (Haff & Nimphius)
  • Heavy resistance → shifts force end of curve (strength gains).
  • Explosive resistance → shifts velocity end (speed gains).
  • Mixed resistance (heavy + explosive) → expands both dimensions → superior power output.

Sample Exercise Matrix (Force vs Velocity Emphasis)

  • Power Clean – High force • High velocity (true power move).
  • Back Squat – High force • Low velocity (strength-dominant).
  • Jump Squat – Low force • High velocity (speed-dominant power).
  • Depth Jump – High force (gravity + landing) • High velocity (immediate rebound).
  • Designing a session with 3/4 movements stressing high force and 3/4 stressing high velocity → robust power adaptation.

Environmental Stability

  • Firmer surfaces (hardwood, gym floor)
    • ↑ tendon stiffness → ↑ elastic energy storage & return.
    • Minimizes energy loss into the environment.
  • Soft / unstable surfaces
    • Dissipate energy; ↓ peak power; used sparingly (e.g., for specific proprioceptive goals, not peak power).

Practical / Clinical Implications

  • Match load (~30 % 1-RM) and cue “as fast/quickly as possible” for most power drills.
  • Keep eccentric phases brisk (<4 s) and teach immediate transition (stretch-shorten).
  • Program abundant rest; quality over quantity is paramount.
  • Ensure surface & environment enable, not hinder, elastic energy return.
  • For older or novice clients: emphasize safety, clear cueing, and gradually progress velocity demands.

Ethical & Safety Considerations

  • Risk mitigation: Complex/high-force movements scheduled while fresh; monitor technique deterioration.
  • Individualize prescription: Health status, orthopedic limitations, reaction time, and cognitive load.
  • Document rationale for every variable (selection, order, intensity) for transparency and continuity of care.