Sprinting is guaranteed to burn bodyfat, particularly when performed in the morning before eating breakfast.  Sprinting is a superb fat-fighting exercise because it involves short bursts of energy, significantly elevating your metabolic rate.  The recommended manner in which to perform sprints is in an interval fashion with progressive intensity levels as your body adapts to the training stimulus.  Never jump right in to full-on sprints at maximum intensity (e.g., 100% HRR) until your body has adapted.  Best to gradually work up to intensity levels which are at submaximal intensities (e.g., 70 to 90% HRR).  Be sure to take it slow and work up to increased intensity levels.  Besides intensity level, consider the frequency and duration of your sprints.  Better to be conservative on these aspects as well.  Twice per week at 30 to 45 minutes is adequate to achieve fat-burning results when sprinting.  Only sprint on a cushioned surface such as a running track, artificial turf or grass--avoid pavement to spare your hip and knee joints.  Lastly, be sure to wear a good pair of running shoes with a flat sole--minimus New Balance shoes are ideal.  

     Walking is the best land-based exercise that spares your joints from injury and pain.  The best thing about walking is anybody can do it no matter the skill level.  To make walking a great cardiovascular workout in which you'll burn more calories, be sure to walk at a quick pace.  You should be walking as fast as you can short of running (i.e., about four miles per hour).  In order to effectively do this, you should pump your arms with the elbows in a bent position (i.e., about a 90-degree angle) while swiveling your hips.  This allows your body to move forward more quickly and efficiently due to less side-to-side movement.   Pumping or swinging your arms at the shoulders in sync with your feet also enhances forward momentum.  Be sure to maintain good posture by keeping your chin up, head level, shoulders relaxed, and back straight.  Speed walking is one of the safest and easiest exercises you can do to get in a superb cardiorespiratory workout.  Start with a 20-minute walk three to five times per week and gradually increase the pace on a weekly basis.  You can make your walks more interesting by wearing a weighted backpack and/or going on hill walks.  You can also try interval walks in which you alternate your pace from fast to a slower speed.  

BOTTOM LINE:  Research has indicated that those who tend to walk faster have lower mortality rates but any kind of walking is better than no walking at all.  Just be sure to put on a pair of comfortable, flexible shoes and get out there and walk!

     Besides affecting your cardiovascular and pulmonary system, performing cardio exercise regularly affects your body composition, hormonal system, skeletal system, metabolic system, cognitive sytem, immune system, athletic performance, and quality of life.

     Power walking involves walking at a brisk pace (e.g., 5 miles per hour).   This is a superb exercise for those who want to spare their joints (e.g., back, hips, knees, ankles) from high impact and for those who may have orthopedic issues (e.g., arthritic knees).  Power walking can provide cardiovascular benefits comparable to running.  It entails having one foot touching the ground at all times with the front leg being relatively straight when it contacts the ground.  To get the most out of power walking, you should strive to move as quickly as possible in order to burn more calories and become more fit.  Here are some tips to better your technique and to help move at a faster pace:

• Keep you chin up, head level, shoulders relaxed, and back straight
• Pump your arms in front of your shoulders with bent elbows (i.e., about a 90-degree angle)
• Keep your arms tucked close to your ribs
• Swing your arms forward rather than crossing the center of your body
• Avoid having your elbows rise above your chest when swinging your arms
• Avoid having each fist rise higher than your buttocks during the backward swing
• Strike the ground with each heel with your toes up
• Avoid bouncing or swaying your upper body
• Keep your hips in line with your shoulders
• Keep your hands closed in a fist but not clenched
• Step with one leg and swing your opposing arm in sync with your stride
• Swivel your hips, allowing for natural rotation to occur
• Push off with the ball of your back foot
• Take relatively small steps to avoid overstriding
• Begin with a 20-minute walk several times per week and gradually pick up the pace each week
• Vary your routine (i.e., carry a weighted vest or backpack, perform hill walking, perform intervals, perform treadmill walking)

BOTTOM LINE:  Walking is a respectable exercise and is certainly better than being sedentary.

    Contrary to a popularly-held belief, cardio generally does not burn more calories than weight training.  I say "generally" because so many confounding factors play a part (i.e., duration, intensity, interval training, etc.).  Taking into account the same duration and comparable intensity levels (i.e., METS), weight training burns more calories than cardio.  The primary reason for this is twofold:

1. Weight training promotes muscle mass preservation and growth
2. Muscle is a highly metabolic tissue which stimulates caloric expenditure for up to 36 hours after the weight training session, a condition known as EPOC (Excess Post-exercise Oxygen Consumption).  

BOTTOM LINE:  If you want to burn more calories in order to lean out or lose body weight, be sure to lift the weights!
Note:  Steady-state cardio generally does not cause EPOC although interval and HIIT cardio sessions do cause EPOC.  

     The answer is simple although the people who use these machines probably are not aware of why they use them.  The reason people tend to opt for the elliptical machine rather than most other machines is because it's very easy on the joints and does not require much resistance to move the body.  In other words, the elliptical machine is the easiest cardio activity to do.  Because it is easy, people naturally want to use it rather than to try a machine that might take them out of their comfort zone.  
    The elliptical machine can be very useful for older adults or those with arthritis, but for most people it's not a very efficient tool to burn calories.    The winner in the caloric expenditure department goes to the treadmill, followed by (from highest to lowest caloric expenditure) the stairstepper (stepmill), the rowing machine, the upright bike, and finally the recombinant bike. 
    The reality is that, in general, the elliptical machine does not elevate the heart rate nor does it burn bodyfat adequately.   This is due to the fact that movement on these machines relies primarily on momentum rather than resistance.  Momentum is simply the product of a body's mass and its velocity.  Just as in weight training, if you move the joints quickly (increasing velocity), momentum increases while resistance decreases.  The net result is essentially less real work being done since less force (resistance) is exerted.  Now you know why people like to move quickly on the elliptical machines:  it makes the exercise easier!  
    No matter which machine you choose, be sure not to lean most of your bodyweight on the hand rails for support.  These railings are designed for your balance, not for support.  By leaning predominantly on these railings, you'll reduce your caloric expenditure because your lower body will not be working as hard as it should.   Straighten your posture by pulling your shoulders back and looking straight ahead.  Rest your hands lightly on the rails to get an optimum workout.   If you still cannot resist leaning heavily on the rails, you need to reduce the intensity on the machine--you're pushing way too hard.  On the other hand, if you can read a book or comfortably breathe through your nose while doing cardio, your intensity level is way too low.  Step up the intensity!
    
    Bottom line:  if you want to burn serious calories, you have to work hard to do it--sorry, working out on the elliptical machine does not qualify, in most cases, as hard work.  Get out of your comfort zone and hit the treadmill, stairstepper or rower instead.

     Even though the distance is the same, you will actually burn more calories while running as this exercise is much more intense than walking.  Intensity means a higher exercise heart rate, greater muscular movement, and more energy to move your body faster.  Also, consider that both feet will be off the ground simultaneously when running in order to maintain a long stride length whereas walking entails one foot on the ground at any one time.  The difference in calories between running versus walking the same distance depends on many factors (e.g., body weight, speed, etc.), but the amount could be about 30 or more calories per mile.  
     Bottom line:  Running burns more calories in less time but walking is less traumatic on the joints.  Therefore, if you prefer to walk rather than run be sure to walk longer distances or at a faster pace in order to burn higher calories comparable to running.   

     More and more research lends credence that High Intensity Interval Training (HIIT) is a great way to lose body weight or bodyfat.  No longer is the standard protocol of performing low-intensity (e.g., 50 to 65% HRR) cardio exercise recommended as the only way nor the best way to burn bodyfat or lose body weight.  Low-intensity cardio is good and can be effective, provided you exercise for relatively long-duration periods (e.g., 45 minutes per session).  Nowadays, who has the time for that!  Enter HIIT training.  
     HIIT should not be confused with interval training.  The distinction is that HIIT involves extremely-high intensity levels (e.g., 85 to 100% HRR) for very short periods (e.g., 10 to 30 seconds) coupled with low-moderate intensity levels (e.g., 50-65% HRR) whereas interval training usually involves moderately-high intense levels (e.g., 65 to 85% HRR) for relatively longer durations (e.g., 30 seconds to 3 minutes) coupled with low-moderate intensity levels (e.g., 50-65% HRR).
     Here are the benefits to performing HIIT:

• Burns more body fat due to a greater increase in cellular mitrochondrial formation compared to traditional, longer-duration cardio
• Causes a greater "afterburner" effect in which metabolic rate is elevated for a longer duration (e.g., up to 24 hrs)
• Shorter cardio sessions (e.g., 20 mins) that are less boring
• Improves athletic performance in sports requiring varying intensity levels
• Less adaptation than low-intensity cardio training which means your body does not readily adjust to the intensity levels--this helps to burn more bodyfat
• Causes blood sugar control
• Less likely to cause muscle loss due to more activation of muscle fibers and the relatively short duration of HIIT compared to longer duration cardio

      Here are the cons to performing HIIT:

• Not for beginners as the technique is very challenging
• Not for lazy people as the level of motivation required must be high since better fat-burning results occur when getting out of your comfort zone
• Not for people with cardiovascular problems
• Can easily cause overtraining (HIIT should only be performed 1-3 days/wk)
• Increases the risk of injury
• Does not necessarily burn more calories than longer, moderate-intensity cardio
• Can dramatically increase stress levels on the heart and muscles
• Not recommended for people with orthopedic problems due to a greater impact on the joints

     HIIT training should be performed infrequently due to its high-intensity characteristic.  Infrequently means no more than two to three times per week.  Performing HIIT any more than three times per week increases the risk of overtraining of which symptoms may include muscle catabolism (read:  muscle burning).   Generally, HIIT training is a relatively advanced technique due to its high-intensity range and increased risk of injury.   When you do HIIT, be sure to do it sparingly.   You can perform HIIT while running, cycling, swimming, or stair climbing.
     No matter which cardio training you choose to do, the bottom line is that you should burn several hundred calories per session.  The best part is that even after you're done exercising, the "afterburner" effect will occur.  That is, your metabolic rate will be stimulated to continue to burn much more calories than a sedentary person while resting.  How great is that?!!  So don't neglect your cardio!