Up until just a few years ago, almost all 40-yard dashes for high school prospects were hand-timed, often by their own high school coaches.

That led to some hilarious discrepancies between players' times as recruits and as NFL prospects, with some allegedly getting slower despite being enrolled in high-quality training programs for four years.

If we go by hand-timing at the 2013 combine, we're left to think former Notre Dame running back Theo Riddick got 0.28 seconds slower in college. We’d think one LSU offensive lineman, P.J. Lonergan, got 0.60 seconds slower. It doesn’t add up.

But for some recruits, we have more accurate numbers these days. We don’t have verifiable 40 times for everybody, and plenty of recruits still tout eye-popping, hand-timed results. Recruits who participated in Nike’s The Opening recruiting showcase after their sophomore or junior years of high school, though, have partially laser-timed results.

The NFL now uses a half-laser approach, where the timing is hand-triggered when the runner starts, but his finish is motion-sensed. That’s a little bit more accurate, and that’s what The Opening uses as well.

The former elite recruits who tested at the combine posted faster 40 times after college than they did before it.

This only includes players who ended up making the combine. Just about every player beefs up while he’s on campus, but most of the players whose speed we can measure didn’t get slower while they were packing on extra poundage.

We’ve cross-referenced available players’ 40 times from the 2013 Opening, which also uses a half-laser method, and this year’s combine. Here are the splits:

40-yard dash times over the years for 2017 NFL draft prospects Player Position College Opening 40 Combine 40 Change Player Position College Opening 40 Combine 40 Change Deshaun Watson QB Clemson 4.89 4.66 -0.23 Montae Nicholson DB Michigan St. 4.6 4.42 -0.18 Raekwon McMillan LB Ohio St. 4.79 4.61 -0.18 KD Cannon WR Baylor 4.58 4.41 -0.17 JuJu Smith-Schuster WR USC 4.71 4.54 -0.17 DeShone Kizer QB Notre Dame 4.96 4.83 -0.13 Josh Malone WR Tennessee 4.49 4.4 -0.09 Malachi Dupre WR LSU 4.58 4.52 -0.06 Budda Baker DB Washington 4.51 4.45 -0.06 Quincy Wilson DB Florida 4.6 4.54 -0.06 Curtis Samuel WR Ohio St. 4.36 4.31 -0.05 Adoree' Jackson DB USC 4.44 4.42 -0.02 Teez Tabor DB Florida 4.64 4.62 -0.02 Artavis Scott WR Clemson 4.62 4.61 -0.01 Jamal Adams DB LSU 4.48 4.56 0.08 Travis Rudolph WR Florida St. 4.52 4.65 0.13

Of course, this doesn’t apply to every recruit. One example of how far off high school numbers can still be, if they’re not being measured at a standardized location: East Carolina WR Zay Jones.

Another example why recruiting rankings will always be an inexact science: Zay Jones

HS 5-11/170, 5.08 40#NFLCombine 6-2/201, 4.45 40 — Barton Simmons (@bartonsimmons) March 6, 2017

It makes sense that most players get faster during their time in college. Despite adding muscle and/or fat, they’re spending their offseasons in finely tuned conditioning programs. They’re doing workouts that increase their explosion, a critical trait when running the 40.

The half-laser method of timing a 40 involves human error, because a hand-starter can’t be fully precise about when a runner starts to move. But now that the combine and at least one recruiting event are on the same system, we can track some changes a little bit better.