[M T]

Huske and Manuel won silvers in the 4 x 100 free relay.
The "response time"  is between when one swimmer touches the wall and the next leaves the blocks. Desirable is between 0.1 and 0.2 seconds. Huske's was 0.00!! If she had left the blocks any earlier, the team would have been disqualified! That was a close one.

Actually, a reaction time at these Olympics of -0.03 in a swimming relay is legal, but -0.04 is a disqualification.
Basically, this is a measure of the error tolerance of the equipment.
For the explanation, see this SwimSwam article from the previous Olympics.  Note: The timing system at the Paris Olympics swim venue is Omega.

For an NCAA rational of how a -0.07 reaction time in a relay was allowed, see this SwimSwam article.

For a (undergraduate?) report on a comparison of relay and flat start times (2015), see here.  (At first glance, I disagree with the premise that the relay time is a "reaction" time: Relay starts are not really reaction times but are what the diver feels is comfortably close, but safe, depending upon the risk/reward ratio. But the paper concludes the average relay start is about 0.4 faster than the average flat (ie, non-relay) start (Hmm.. the paper says 0.39, but flat start average - relay start average = 0.71 - 0.26 = 0.45  ??.))

For an article on the 0.10 reaction time for track athletes, see here.

I wish I knew more about the errors in the swim sensors (touch pad & starting block).  I have long felt that the touch pads have an error of this magnitude and that some races have been decided by a differential in recorded times (of 0.01 or 0.02) that seemed contrary to camera views of first contact with the pad.  Note that 0.03 is about the time between one frame and the next at a traditional 30 Hz video, but most video is faster now.  There should be high speed cameras overhead at the big FINA events (in case of electronic timing failures).

[M T]

Huske and Manuel won silvers in the 4 x 100 free relay.
The "response time"  is between when one swimmer touches the wall and the next leaves the blocks. Desirable is between 0.1 and 0.2 seconds. Huske's was 0.00!! If she had left the blocks any earlier, the team would have been disqualified! That was a close one.

Actually, a reaction time at these Olympics of -0.03 in a swimming relay is legal, but -0.04 is a disqualification.
Basically, this is a measure of the error tolerance of the equipment.
For the explanation, see this SwimSwam article from the previous Olympics.  Note: The timing system at the Paris Olympics swim venue is Omega.

For an NCAA rational of how a -0.07 reaction time in a relay was allowed, see this SwimSwam article.

For a (undergraduate?) report on a comparison of relay and flat start times (2015), see here.  (At first glance, I disagree with the premise that the relay time is a "reaction" time: Relay starts are not really reaction times but are what the diver feels is comfortably close, but safe, depending upon the risk/reward ratio. But the paper concludes the average relay start is about 0.4 faster than the average flat (ie, non-relay) start (Hmm.. the paper says 0.39, but flat start average - relay start average = 0.71 - 0.26 = 0.45  ??.))

For an article on the 0.10 reaction time for track athletes, see here.

I wish I knew more about the errors in the swim sensors (touch pad & starting block).  I have long felt that the touch pads have an error of this magnitude and that some races have been decided by a differential in recorded times (of 0.01 or 0.02) that seemed contrary to camera views of first contact with the pad.  Note that 0.03 is about the time between one frame and the next at a traditional 30 Hz video, but most video is faster now.  There should be high speed cameras overhead at the big FINA events (in case of electronic timing failures).