My first cycle I found it much harder aswell.. Legs would get very tight. But my first cycle, my diet was far from perfect.. This time around, I haven't had to supplement taurine or potassium, and I have had any cramping issues or tightness issues. Granted it's a bit harder, but not that much harder.
I'd check your diet's salt intake, and shave it down wherever possible... make sure your getting addequate potassium, and more importantly drink alot of water... I drink 3 gallons a day minimum.
And bump on glen.. my first cycle, liked to push my cardio hard and fast 150-160+ Heart rate for 20minutes. This time, and from now on, I perfer to work 30-45 minutes of 130-140 beats per minute, i find at this rate, I manage to avoid any feelings of lactic acid build up or burn... but if I try to push it, I can see that it may build up quite quickly, making it a real bitch.