Effects of Training Age Over 4 Years in D1 Football (15 Years of Data)

Collegiate football athletes train in highly structured environments with robust strength and conditioning (S&C) and nutrition support.

Coaches expect steady progress, but the rate of improvement often slows with time.

The aims of this study were 2-fold:

• 1) Describe four-year changes in strength, power, speed, and body mass by position.
• 2) Quantify year-over-year rates of change to test the “law of diminishing returns.”

How much do D1 football players actually improve each year in strength/power/speed/body mass, and when do those gains start to slow?

What Did the Researchers Do?

Researchers performed a retrospective analysis of 15 years of testing data from a single D1 program; 512 athletes, 2,628 observations.

Positions

• 11 positional groups (e.g., OL, DL, LB, WR, CB, RB, TE, QB, S, specialists).
• Athletes remained in their assigned group for analysis.

Tests

• Strength: 1RM bench press, back squat (direct or Epley-estimated from ≤5 reps). Technique and depth standardized.
• Power: Vertical jump (Just Jump mat, arm swing allowed with strict landing), standing broad jump.
• Speed: 40-yard sprint on indoor turf with Brower electronic timing.
• Body mass via calibrated physician scale.

Analysis

• Linear mixed models with athlete as random intercept; estimated marginal means; Tukey-adjusted pairwise comparisons; Cohen’s d effect sizes to describe the magnitude of year-over-year change.

What were the results?

Big Progress Early

• From Year 1 to 2 across the entire cohort, effect sizes were large for bench (d≈1.63) and squat (d≈1.62).
• From Year 3 to 4, changes were only small (bench d≈0.45, squat d≈0.26).

Modest Improvements for Power and Speed

• Year 1 shows the most significant improvement in vertical jump, broad jump, and 40-yard sprint; subsequent years show progressively smaller gains.

Bigger by Year

• significant improvement in vertical jump, broad jump, and 40-yard, especially in line positions, with the largest increases early and smaller increments later.
• The cohort mass rose each year with a diminishing magnitude.

Positional Insights

• OL & DL: Highest body mass and absolute strength; slower sprint times; continued but tapering strength gains.
• WR/CB: Lightest, fastest, and best jumpers; still improve strength early but later gains are smaller.
• LB/TE/RB: Middle profiles; strong early gains in strength and modest improvements thereafter.

What Does This Mean?

Training Age Matters

• The first collegiate year offers the largest window for shifting the needle in strength and meaningful improvements in speed/power.
• Plan to front-load general development.

Expect Tapering ROI

• After Year 2, improvements occur, but at smaller magnitudes.
• Programs should pivot toward quality, specificity, and individualization rather than chasing linear load progressions.

Position-Specific Targets

• Use the positional trends to set realistic benchmarks and guide emphasis (e.g., OL/DL continue strength but manage mass; WR/CB refine speed and power qualities).

Limitations

• Single program data may limit generalizability across conferences or training philosophies.
• No in-season vs off-season split in analysis; we see yearly snapshots rather than microcycle influences.

Coach’s Takeaway

• Year 1 is critical for development ⮕ Prioritize robust full-body strength progression, foundational power work, and sprint mechanics.
• Expect smaller gains in years 1-2 ⮕ Focus on individual limiting factors, micro-dosed exposures, and sport-specific transfer.
• Benchmark by Position ⮕ Use the positional profiles to set targets and align body mass, strength, and speed goals with role demands.

I hope this helps,

Ramsey

Reference
Morrison M, Mann JB, Read DB, Thurlow F, Cowley N, Silverthorne K, McMahon E, Weakley J (2025). Longitudinal changes in strength, power, speed, and body mass in American football players: Diminishing returns as training age increases. International Journal of Sports Science & Coaching.