Ketosis, the dietary state where you burn fatty acids as your primary fuel instead of sugar, presents certain difficulties when attempting to work out. Glycogen, the preferred fuel for muscular contractions, remains in short supply in the absence of dietary carbohydrates. Any low-carbohdyrate diet can challenge your ability to workout, but with a few modifications, you can train with intensity.
Lift in short, intense sessions. Resistance training provides numerous benefits, including muscle gain and fat loss, but does not require marathon sessions. If you are training for longer than an hour in the gym, you are not training hard enough.
Train using lower-repetition sets. Keep your sets to 10 reps or less, and if this means you need to increase the weight, still select a weight that you can safely control. If you want more volume, perform more sets. This will allow your depleted glycogen, or sugar reserves to replenish slightly between sets.
Perform intense cardiovascular exercise. Sustaining marathon-level endurance training without carbohydrates is extremely difficult. If you wish to run three miles, but the lack of carbohydrates limits your performance, run your distance in interval fashion. Run as far as you can, walk until you recover, then continue at your run pace. This can be duplicated for any form of cardiovascular exercise.
Eat a small amount of carbohydrates post-workout. Following your workout, your blood sugar is extremely low and your body will shuttle sugars you consume directly to your muscles. This will help refill the muscle glycogen that you burned during training. About 25 to 50 g of dextrose or maltodextrin is ideal, but start with only 25 g and determine the effect on your diet.
Consume a small amount of whey protein with your carbohydrates following a workout. In addition to burning sugar, your body will break down amino acids during training. According to a 2007 study published in the "Journal of the International Society of Sports Nutrition," a combination of whey protein and dextrose improved recovery and promoted muscle growth when consumed post-workout.