If you are generally looking to fuel your workout (ex. 60 min. class or 90 min. mixture of weights and moderate cardiovascular activity) it is important to ingest a balance of carbohydrates and protein approximately 60-90 min. before your workout.
The types of carbs you should ingest are those that are low on the glycemic index. These types of foods are most appropriate because they are digested more slowly and can provide you with a longer lasting fuel source during your workout. Protein sources will provide your muscles with the building blocks they need to stimulate growth & reduce recovery time.
Examples of carbohydrates that are low on the glycemic index are oatmeal, rice, various types of beans, flax seeds, peaches, strawberries & most vegetables. For protein, choose meat sources. Their slow digestion rate will ensure that your muscles are given an adequate amount of fuel right until the very end. Meat sources will also provide your body with a natural source of creatine for those last few reps of each set.
Depending upon your goals it is important to know how much you should be eating prior to your workout and ensure that it lies within your recommended daily caloric intake. Generally a person should ingest roughly .25g of carbs multiplied by your total body weight and .25g of protein multiplyed by your total body weight. For example, if someone weighs 195 lbs they would be required to eat a mixture of 48.75g of carbs and 48.75g of protein 60-90 min. before working out.
Again each individual is different and depending upon your goals and the type of activity you are engaged in, the aforementioned recommendations may change. Otherwise, go ahead and power-up before Powerfit. Your body will thank you!