Back off on the intensity, increase the time you are doing it...........having pain in the knees is your body telling you, you are overdoing it! If you continue at the rate you are doing it, you are just going to injure yourself. Carrie said it best, Rome was not built in a day

You will be able to increase the intensity as your endurance and muscle strength improve.
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Beginning weight: 278
Current weight 192
Total inches lost up to 1/22/07 75 inches
Total weight lost as of 2/19/07:
86
Starting BMI: 43.5
BMI as of 2/19/07: 32.1
Be ready for the twists, and the unexpected, because you know it will come and try to side track you. It's in those moments that your true character and commitment are tested, how you react is a great indication of how or if your life has truly changed. Brian ~ Biggest Loser Season 3