You know you should be spending time strength training, but you already spend a lot of time at the gym doing cardio and don't think you can fit in toning sessions. Don't assume you have to spend hours lifting weights — it doesn't take much to start seeing results. Start with 20 to 30 minutes of strength training sessions twice a week. Lift dumbbells, do exercises that use your own body weight such as resistance band, try those weight machines. Remember to work all your muscle groups, not just your upper body. Once you fit that into your schedule, work on adding another day. You'll notice that you're body is stronger overall, your muscles have more definition, and you'll feel more powerful when running, biking, or doing other cardio.