at work, currently doing one's work
There was nobody on duty when we arrived at the swimming pool.
Jogging Tips and Guidelines
Dont start too fast
Runners who are new to speedwork sometimes make the mistake of running way too hard and fast for every interval. You should put in a good effort, but dont run so fast that your breathing and heart rate are totally out of control. Try to run your intervals consistently so that your last one is the same effort as your first. If you feel like you have nothing left for your last interval or the last few minutes of a tempo run, you did it too fast.