Last Night I woke up from a dead sleep to severe cramps in both hamstrings. It took me 15 minutes to work them out. Yesterday I completed my weekly full leg workout and the only change I made was replacing RDL with Good Mornings. 4 sets 2x10@45 and 2x10@65. After lifting I completed 22 minutes of walk/sprint on the treadmill. Pre-workout I drank ON whey and MP Assault pre workout. During and immediately post workout I drank MP BCAA. Upon arriving home I drank a ON Casein shake with 12oz unsweetened Almond Milk, 2 tbsp PB and 1 banana. I drank a total of 191oz of fluid yesterday. I am 6'1" and weigh 315. I have been work legs very hard for the last 6 months and I have never had this happen before.
Any thoughts on why this happened. DOMS or something else?