“Burn more than 1,000 calories by doing this group fitness class.” “Maximize fat burning with high intensity interval training.” “Yoga can cure almost everything!” We come across headlines like these everywhere, from magazines to blogs to Twitter. But should we heed to all this advice?

Many popular fitness practices often come from studies and/or research conducted on a particular fitness matter, yet many factors play a role in the results and cannot be considered one size fits all.

The key here is to understand what is behind some common fitness expertise and how you can make the most out of them. There are many out there. Here is the first of a two-part look at some popular advice and what they really mean.

1. “High intensity cardio: better results in less time”

It has become the most popular fitness advice: ditch the hour-long, low intensity cardio for a 20 minute high intensity interval training (HIIT) workout in which you alternate short periods —from 30 to 60 seconds at maximum intensity followed by a recovery period of the same duration or longer. Boom! You burn more calories and finish sooner.

Not so fast. HIIT definitely will add a metabolic stress that ignites the endocrine system in such a way that even after your session ends you still burn calories. In fact, studies show this effect can last more than 14 hours. The benefits show up in your waistline and your heart in terms of better blood pressure and aerobic capacity.

However, when looking at these studies, one important element stands out: the interval intensity is around 90 percent of VO2max. In other words, very, very high intensity. You can barely say a word or two.

As you may have experienced, this out of breath state is hard to maintain and can be quite painful, and not something everyone can do. So you may not see the promised results because you cannot consistently reach this high intensity stage.

My Advice: HIIT is a great way to tax your metabolism, muscles and heart. But if you cannot hit the high level, tweak your workouts so you can still receive the same overall benefits. For example, if you have to lower the intensity, then the duration should go up. Here are some other tips for a more doable interval training session:

-       Perform a 10 minute low to increase moderate intensity warm-up.

-       Do 20 minutes HIIT —60 seconds-30 seconds or 60-60 seconds. For the high intensity exercise, simply make sure you work hard, but do not go all out. Your effort should feel like you can complete the interval without being exhausted. Get out of your comfort zone so you can speak a short sentence.

-       Perform a 10-minute moderate to low intensity cool down.

2. “Burn more than 1,000 calories per hour by doing (fill the blank)”

This headline makes a splash in almost every fitness magazine whether the story is about whole body resistance training, Zumba, cross-fit or boot camps. People believe any activity perceived as a high intensity one easily burns high-figure calories. But that is not necessarily true.

“A big factor in determining the number of calories expended is a person’s body weight,” says Richard Lopez, Ph.D., professor of exercise sciences at Florida International University. “For example, if a 200-pound person exercises for an hour and we assume that he or she exercises with the same efficiency of a 100-pound person, then the 200-pound person will expend twice as many calories.”

But it’s not that simple. You also have to take realistic intensity into consideration. It is difficult for anyone to burn 1,000 calories per hour, let alone someone who weighs 200-plus pounds. To expend this amount per hour you have to consume the approximate equivalent of 200 liters of oxygen/hour. For a 132-pound female this is the same as running a 6-minute mile pace for an hour.

Likewise, other variables, such as movement efficiency and the degree to which movements are actually performed, factor into the equation. “The bottom line is that a 1,000 calories per hour is heavy to very heavy exercise,” says Lopez.

My Advice: Don’t focus on calories, but on generating enough effort. Make sure you break a sweat. True, the harder the intensity, the more calories you will burn, but don’t think that a single class will do the trick if you don’t put out the right effort. Put in the work and you will see and feel the results.

3. “Do yoga to prevent back pain”

Anyone who has tried yoga knows it helps build core strength. And why is this so important for your back? Studies show that non-specific chronic low back pain may be related to lack of strength in the core muscles: abdominals, glutes, hips, and lower back muscles.

In fact, one study showed that 10 weeks of yoga intervention combining breathing, stretching, strengthening and mindfulness exercises, increased quality of life, decreased fear avoidance beliefs, and decreased pain disability in people who experienced non-specific chronic low back pain.

But this does not mean ALL yoga is ideal for tricky backs. Some styles like Ashtanga or high intense hybrids like “Power Yoga” may be too intense. However, most yoga classes are adoptable to an individual’s physical limitations, while others are designed to address specific health issues, including the back and core.

Still, injuries in a yoga class can occur, especially when you try too hard or not mindful. “You can’t zone out in a yoga class —that is setting yourself up for injury,” explains Aileen Febles, Certified Yoga and Prenatal Yoga Instructor at The Sports Club LA/MIA.

While men often see their natural lack of flexibility as a weakness, when it comes to injury prevention it can be a valuable asset. A less flexible person will have a more challenging time, but they won’t get injured as quickly as someone more flexible. The reason?  “They won’t be able to push and strain their ligaments or muscles like someone who is flexible and doesn’t know or understand their level of boundaries.”

My Advice: Do yoga for a stronger back, but be careful. Here are some other tips from Febles to back up your back:

-       Iyengar Yoga is the best yoga style for anyone dealing with an acute or chronic injury as it utilizes many props and other supportive equipment.

-       If you experience acute lower back pain, do not engage in any forward bends without proper support like blocks or straps. This will help you from aggravating a sore back by putting too much compression on the spine.

-       An experienced teacher should guide you during twisting poses to ensure flexion takes place through the hip joints and not the lower back. Otherwise, the facet joints can become irritated and the posterior ligament can be strained, which can lead to further injury.

Marta Montenegro is an exercise physiologist, certified strength and conditioning coach and master trainer, who teaches as an adjunct professor at Florida International University. Marta has developed her own system of exercises used by professional athletes. Her personal website, martamontenegro.com, combines fitness, nutrition and health tips, exercise routines, recipes and the latest news to help you change your life but not your lifestyle. She was the founder of nationally awarded SOBeFiT magazine and the fitness DVD series Montenegro Method.

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