Have a tough fitness question? Getting a clear answer can be difficult, especially when money is involved. Personal trainers are often paid hourly so answers to tough questions may include pricey training sessions. Similarly, there are many companies that offer their products as the solution to problems with weight loss, performance or muscle building.

Fitness enthusiasts looking for information have to consider the source. Professionals with formal backgrounds in kinesiology can provide insight grounded in research, not commission payments.

With the help of two kinesiologists, here are answers to six complex fitness questions:

1. How long does it take to build muscle?

Dedicated weight lifters will notice a strength increase before seeing the scale increase with muscle weight, said Kent J. Adams, PhD, director of the Exercise Physiology Lab at California State University, Monterey Bay.

“You’re looking at a couple months time to visibly see change,” Adams said.

Seeing visible changes involves consistent training sessions. Lifters working the full body at once will need at least two sessions per week. Four sessions are needed per week if lifters work only certain parts of the body per workout.

Exercisers with a set goal of building muscle should commit at least three 45 minute sessions to weight lifting each week, said Eric Cressey, who holds a MA in kinesiology and owns Cressey Performance in Hudson, Mass.

2. How often should you exercise?

“You need to accumulate a minimum of four hours of exercise a week for general health,” Cressey said. “I’d like to see more around six hours.”

A competitive power lifter, Cressey exercises six days a week, leaving one day for rest. Four of his workouts are more challenging while two are lighter conditioning.

Exercisers with less time to commit to fitness should establish a baseline of activity – walking the dog, cycling to work, gardening – and then add a blend of aerobic and resistance training three to five times per week, Adams said.

3. How can you burn fat?

This question has many answers and sometimes it’s just stuff people want to hear.

“Trainers love to tell people there is this optimal fat burning zone, but the mathematics don’t work out,” Adams said.

To best burn fat, Adams recommends having a varied intensity training program that incorporates both high and low interval activities.

Exercisers are also recommended to focus on fat away from the gym. “Get your diet in line,” Cressey said. “Reduce carbohydrates, particularly refined ones. every time we eat carbs, we secret insulin, which we know works counter to burning fats.”

Frustrated exercisers should also remember there is value in working out, even if fat isn’t melting away. “Anything you do is burning calories,” Adams said.

4. How do overuse injuries happen during outdoor activities?

It makes sense a softball pitcher could have a shoulder injury from overuse. Or a marathon runner experiences knee pain. But how do overuse injuries happen to regular exercisers?

Some injuries happen from taking on too much too soon. Others come from a lack of cross training, Cressey said.

Overuse injuries are a common complaint in Cressey’s training business. he particularly sees runners with knee, hip, and back problems.

“Institute a variety of exercises,” Cressey said. “Most overuse comes from doing the same thing over and over again.”

Including a variety of exercises can help prevent burnout. Adams recommends cycling through several aerobic activities such as running, rowing, and taking group exercise classes.

5. What are the best mid workout fuel – excluding gel packs and power bars?

Put away the protein bars – both Cressey and Adams said the average exerciser needs only water during a long workout. Endurance athletes, such as marathon runners, can use gel packs and Cressey said there is some research suggesting these products improve recovery.

Shorter workouts don’t require extra fuel and Adams said few people will become glucose depleted. Exercisers are better to focus on adapting a consistent daily diet. “The key to a 60 to 90 minute workout is to maintain a good solid nutrition in your daily life,” Adams said.

Post-workout fuel is important and Cressey recommends a low-carb option such as fruit yogurt.

6. What should you do when you just want to quit?

Even the most committed find themselves watching the gym clock slowly tick. in low moments, Adams recommends switching activities. “Mental and physical rest is part of your variation in training,” Adams said.

Mental rest can mean taking a break from the treadmill and trying a running trail. Or swapping a cycling session for a spin class. Lifters tired of training can meet with a personal trainer and identify new and interesting exercises to incorporate into their routine, Adams said.

Another option is to pair up with a training partner. “That’s the value of a workout partner,” Cressey said. “You avoid that issue before you begin, you know you’re accountable.”