Race Time Measurement

Hi,

Watching World Cup Skiing on tv, I notice that many skiers, on passing the finish line, appear to put one or both arms down and forward. Why is that? Is it to trigger their finish time as soon as possible? What does trigger the finish time: when the skip tip crosses the finish line, or the front of the ski boot, or a hand placed ahead of the ski boots?

On a similar note, what triggers the start time: when the boots hit the little bar at the start gate, or the start of the last and long horn blast?

I know that the start is triggered by the small 'gate' they push through but the finish i only think is the tip of the ski-i only say this because in skier X and cross country it is measured with the tip

Not being an expert so may be wrong.

Start - there is a little stick about boot height that triggers the clock. When they push it forward it starts the clock. Think of it like the little stick that starts off a drag lift

Finish - I imagine the finish is when the first part of body passes the finish line. To get as far forward as possible the arms are shoved forwards, much the same as runners tip their heads forward when crossing the finish line.

Like I say, i am no expert but makes sense i think

The finish is a light beam which is about 30cm or so off the ground. The skis will pass underneath, so reaching down will give a skier a couple of feet advantage.