Not Sweating During Exercise

Sweat is produced to cool your skin down. Usually when you work out, you get warm and then sweat to cool down. But if you are working out in a cool environment - say not heated very much, then there's no need to sweat. Sweat also depends on how much water you've drunk and how much salt you've eaten. The body needs water, and if you haven't drunk much, will be reluctant to lose any in sweat/urine. And if you've eaten too much salt, salt retains water and holds it in your body.

No, sweating is not neccessary. It is pulling up the heart rate that counts. But, don't over due it. Do not go past 120 beats in a minute.