The first couple of bits of vigorous exercise - 45 minutes of circuit-training outside, 45 minutes of core-focused weight-training in the gym - were absolutely glorious fun; I left the circuit-training so fizzing with energy that I had difficulty working that afternoon, I left the weight-training feeling weirdly upright and amazingly light on my feet. I jog-walked (run for a count of sixty, walk for a count of sixty, repeat) round the block and, while my lungs were definitely not happy, my brain was delighted.
But this has now stopped. After the last couple of gym sessions and the last bout of circuit-training, instead of feeling invigorated, I was feeling completely knackered and distinctly glum. And I can't figure out what it might be that I'm doing differently. It's not that my asthma inhaler has some sort of weird invigorating power, I had to use a fair amount of Ventolin in the circuit-training.