So today was legs day and I was hitting my calves, I was doing barbell raises, my first set was great, I was concentrating on my cavles especially so I could feel it burn like FUUA on every rep, nice and slow.. after waiting around 45 secs - 1 minute I went to hit the second set, and on my first rep my cavles spasmed to shit! seriously it was like I was standing on a vibro-plate?? It wasnt a muscle cramp or anything as it didnt hurt, no pain at all and I could still do the reps perfect but my calves would just spasm and I would'nt feel the pump anymore, whats up? I also did warm up sets and stretching etc..