How to Build a Force-Velocity Profile: 6-Step VBT Protocol

Force-velocity (F-V) profiling reveals whether an athlete is force-deficient (need to get stronger) or velocity-deficient (need to get faster). This individualized diagnosis guides programming far better than generic prescriptions. This guide presents a 6-step protocol for building an F-V profile in 30 minutes using VBT.

The F-V relationship (Hill, 1938) describes the inverse trade-off between force and velocity.

The F-V Curve

Plotting load (force) vs bar velocity produces a linear relationship. The slope reveals individual mechanical bias. Steep slope = force-dominant athlete; shallow slope = velocity-dominant athlete (Samozino et al., 2012).

Force vs Velocity Deficits

• Force deficit: Higher velocity at light loads but rapid velocity drop with load — needs max strength work
• Velocity deficit: Low velocity at all loads — needs ballistic and unloaded power work
• Balanced: Linear F-V profile matches population norms — needs maintenance or mixed work

Related: F-V profiling research.

The protocol takes 30 minutes and requires 4-5 loaded sets.

Step 1: Equipment Setup

• Squat rack with calibrated weights
• VBT device (PoinT GO 800Hz IMU on barbell)
• Spreadsheet or app for data plotting

Step 2: Standard Warm-Up

10 minutes general (rowing/jogging), 5 minutes dynamic mobility, 3-4 specific warm-up sets (40%, 60%, 80% of estimated 1RM) for 3 reps each at max velocity intent.

Step 3: Test Load Selection

For the chosen exercise (typically back squat, bench press, or jump squat), select 4-5 loads spanning the F-V range:

• Squat: 30%, 50%, 70%, 85% of 1RM
• Bench: 30%, 50%, 70%, 85% of 1RM
• Jump squat: Body weight, 20%, 40%, 60% of body weight

Step 4: Data Collection

2-3 reps per load, 2-4 minutes rest between sets. Use the best (highest velocity) rep at each load. Maintain maximum velocity intent throughout.

Step 5: Plot the Data

Plot velocity (y-axis) vs load (x-axis). The best-fit line equation reveals the F-V profile: y = -slope × x + V₀.

Step 6: Interpretation

Compare slope and intercept to population norms or your previous test. Larger deficit determines training emphasis.

F-V profile interpretation drives programming decisions.

Calculating F₀ and V₀

• F₀ (theoretical max force): Load at which velocity = 0 (x-intercept extrapolation)
• V₀ (theoretical max velocity): Load = 0 velocity (y-intercept)
• Pmax (max power): Reached at F₀/2 and V₀/2
• Slope (F-V slope): Steeper = force-dominant, shallower = velocity-dominant

Programming Decisions

• Force deficit (steep slope): 80-90% 1RM heavy strength × 4-6 weeks
• Velocity deficit (shallow slope): 30-60% 1RM ballistic × 4-6 weeks
• Balanced: Mixed 30-85% range × 4-6 weeks

Re-Test Schedule

Re-profile every 4-6 weeks. Optimal profile shifts toward balanced over time. The same athlete may need force emphasis for 6 weeks, then velocity for 6 weeks.

Profile accuracy depends on measurement quality.

PoinT GO Workflow

PoinT GO 800Hz IMU automates much of the protocol:

• Auto-calculation of F₀, V₀, Pmax, slope from session data
• Visual profile plot with comparison to previous tests
• Auto-recommendation of training emphasis based on profile shape
• Export to spreadsheet for coach review

Common Errors

• Insufficient velocity intent: Athletes often submaximal on heavy loads — coach for max effort every rep
• Too few test loads: Need 4+ points for reliable line fit
• Fatigue: Profile worse on fatigued day — test on fresh day only

Common F-V profiling problems.

Non-Linear Profile

If data points don't fit a straight line, check: ① test rep velocity decline (re-test fresh), ② weight calibration, ③ enough velocity variety (use full 30-85% range).

Identical Profile Over Time

If profile doesn't change after training: ① is intent really max?, ② training emphasis appropriate?, ③ adequate recovery between sessions? Re-evaluate program adherence and recovery first.

Profile Worse After Training

Could signal overtraining or change of program direction needed. Cross-reference with autoregulated training velocity baselines and consider a deload week.