It’s the start of the new year, and maybe you’ve made up your mind to become more physically fit.

Exercise offers a host of benefits, from weight loss to feeling healthier to a lower risk of heart disease, cancer, and other medical conditions.

But like many people, you may have already run into one of the biggest roadblocks on the way to a healthier you — lack of time.

If your schedule is already packed, the last thing you want is to waste time on a workout that isn’t getting you results.

So which exercises will give you the most bang for your buck?

For Jimmy Minardi, a personal trainer, yoga instructor, and former pro athlete, this is one of the most common questions he is asked.

In response, he offers this advice: “If you don’t know how to get back into shape or start an exercise program, you have to find out what you like to do.”

Minardi said you could think about what physical activities you enjoyed as a child.

If you played hockey in high school, find an open skate or adult hockey team at a local arena.

If you like talking to people, join a walking or bicycling group. Or find a friend who will work out with you.

But if the gym or boot camps are definitely not your thing, you might want to steer clear of them.

“If you don’t like going to the gym,” said Minardi, “six months later you’re not going to be doing that.”

So in some sense, the best exercise program is not just one that is effective, but one that you will stick with long after many people have abandoned their New Year’s resolutions.

Read more: Physical activity cuts your risk of death »

Is all exercise created equal?

Does that mean any activity is a workout?

Not quite.

Research shows that you’ll start to accumulate health benefits when you exercise at a moderate to vigorous intensity.

That means binge watching your favorite shows on Netflix while lying on the couch is out. So is playing video games (unless you are doing something active like Nintendo Wii).

But many activities fall into the moderate intensity category — like walking briskly, playing baseball, and some types of yoga.

Even dancing and playing sports with your children can get your heart racing enough for health benefits.

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Many people are familiar with calories burned per hour during an activity. For the intensity of exercise, scientists prefer to use metabolic equivalents (METs) — a measure of energy used during an activity.

This takes into account a person’s body mass, which makes it easier to compare activities without knowing how much you weigh.

Sitting quietly has a MET of 1 — this is the baseline.

Hiking has a MET of 6, so on a hike you would use six times the energy as you do while sitting. Doing martial arts has a MET of 10 — meaning it burns 10 times the energy of sitting.

These measurements, of course, are averages. The actual amount of energy burned depends on your exertion.

There are other ways to gauge the intensity of your workout.

“A moderate level is going to be something that you feel takes some effort, but it doesn’t take a tremendous amount of effort,” Jennifer Turgiss, Dr.P.H., vice president of behavioral science and analytics at Johnson & Johnson Health and Wellness Solutions, told Healthline.

Walking like you are late to a meeting is moderate activity. Strolling in the park is not.

A heart rate monitor is another option for measuring intensity of exercise.

“It’s like a tachometer for your heart. It’s an amazing way to connect yourself to your training,” said Minardi, “You learn about how your heart reacts to the exertion rate and it gives you a benchmark.”

Minardi said heart rate monitors can also be used to measure your recovery. As you become more physically fit, it will take less time for your heart to return to its resting pace after exercise.

Read more: What’s your ideal heart rate? »

How much exercise do you need?

The U.S. government’s 2008 Physical Activity Guidelines for Americans recommends that adults do at least 150 minutes a week of moderate-intensity physical activity.

Or 75 minutes of vigorous-intensity physical activity. Or some combination of both.

They should also do two or more days a week of muscle-strengthening activities that target all major muscle groups.

These are the minimum amounts that people should aim for.

New research suggests that it doesn’t seem to matter when you exercise, as long as you hit these minimums each week.

A study published this week in JAMA Internal Medicine found that “weekend warriors” — those who crammed the recommended physical activity into one or two sessions each week — had lower risks for death, compared to sedentary adults.

These findings are similar to a 2015 study that looked at more than 661,000 adults.

Researchers found that people who met the guidelines were 31 percent less likely to die during a 14-year time period.

These benefits increased with more exercise, peaking at three to five times the amount specified by the guidelines. These people had a 39 percent lower risk of early death.

However, “super exercisers” — those who worked out at least 25 hours per week — had a similar risk of early death as those who met the guidelines.

So more is not always best. And it can also be a sign that you’re not working out optimally.

For someone looking to develop and maintain general fitness, said Minardi, "if you're training for more than one hour per workout -- and it's not efficient or smart -- after awhile you're going to get bored with it, and you're going to quit."

Even if you aren’t quite at the minimum guidelines, don’t worry. Some moderate to vigorous exercise is better than none.

In the 2015 study, people who exercised less than the guidelines were 20 percent less likely to die early compared to nonexercisers.

And there are other benefits to small amounts of exercise.

A study last year supported by Johnson & Johnson Health and Wellness Solutions looked at the benefits of five-minute microbouts of moderate walking on a treadmill throughout the workday, compared to sitting for six hours.

Researchers found that these tiny workouts improved mood, decreased fatigue, and reduced food cravings.

This, of course, will not replace a more structured exercise program — combining strength, flexibility, and cardiovascular exercises — but staying active throughout the day could give people enough energy to make healthy choices once they are home.

“When people leave work they are so flagged and tired that even though they might have been sitting and sedentary all day, they no longer have the energy to do a more formal workout, or to make healthy eating choices,” said Turgiss.

For people looking for another short workout, Johnson & Johnson Health and Wellness Solutions also developed a seven-minute workout that combines high-intensity aerobic and resistance training using only your body weight.

It is available as a free 7 Minute Workout or 7 Minute Wellness for Expecting and New Moms app.

Read more: Can cash motivate people to exercise? »

Ramping up the intensity

Moderate-intensity exercise will get you all the health benefits you need.

But ramping things up a notch may give you faster — and more impressive — results.

A 2015 study in JAMA Internal Medicine by researchers in Australian found that risk of early death decreased as people added vigorous exercise to their workouts.

Vigorous exercise includes activities like rugby, rock climbing, hockey, or running.

Although these activities burn energy faster than moderate activities, you are also more likely to injure yourself. Especially if you jump in too quickly.

Running can be hard on the body, with the feet striking the ground with a force many times the body weight.

One 2015 study estimates that for every 1,000 hours of running, 18 percent of new runners, and 8 percent of recreational runners, are injured.

One alternative to running is racewalking. This Olympic sport can burn two-thirds as many calories per hour as running, with much less wear-and-tear on the body.

Recent research, though, is starting to show that even small amounts of vigorous exercise can provide many health benefits.

This is the concept behind high-intensity interval training, which includes brief bursts of exercise, followed by longer periods of light exercise or rest.

Athletes use high-intensity interval training to increase their speed and power, usually as part of a weekly training program that also includes less intense endurance workouts.

But this type of exercise has benefits for recreational athletes and new exercisers, as well, especially for those who are crunched for time.

In a study published last year in the journal PLOS One, researchers at McMaster University, in Canada, put a group of sedentary men through 12 weeks of high-intensity interval training.

This involved three 20-second sprints on a stationary bicycle followed by two minutes of low-intensity cycling. With warmup and cooldown, the whole workout was 10 minutes, one minute of which was vigorous.

At the end of the 12 weeks, men in the high-intensity group saw similar benefits as men who did 45 minutes of continuous cycling at 70 percent of their maximal heart rate — still an active workout, but not nearly as intense as the sprints.

These benefits included greater aerobic fitness, better regulation of blood sugar levels, and improved functioning of the muscles at a cellular level.

The high-intensity group, though, only exercised 30 minutes a week, compared to 150 minutes in the continuous cycling group.

The intense sprints are just what they sound like — intense. So this type of exercise may not be for everyone.

“The benefits of high-intensity interval training rely on people having the ability to exercise at an extreme maximal intensity level for a very short duration,” Jamie Costello, fitness director at the Pritikin Longevity Center + Spa, told Healthline.

If someone isn’t up to this level of intensity, he added, it could “increase their risk of injury and burnout over the long term.”

Less intense forms of interval training, though, can be used to challenge people without overwhelming them.

Read more: Best interval training videos of 2016 »

Too much, too soon

With the new year fresh in mind, it can be tempting to try too much, too soon.

“Getting fit is a lifestyle adaptation and not a short-term fix,” said Costello. “While the promise of quick results may get people excited about trying the latest fad, it doesn’t lead to long-term behavior change.”

It’s also easy to forget that going from a sedentary lifestyle to regular exercise is a big step.

So people often overreach with their exercise program, which can lead to a dead end.

“If you’re up against a workout that is over your head — it’s too hard, it’s not smart, and it’s a little bit too long— after a while you’re just not going to want to go anymore, because it’s too consuming,” said Minardi.

The key to staying fit for the long run, said Costello, is “slow progression, until exercise is a regular part of your life. At that point, the possibilities are endless.”

But even with a well-planned workout, some people may find that no matter how long they exercise, they see very little improvement in their health or fitness.

As a result, they may blame their genes or a lack of discipline. But it could be that they are “nonresponders” — one type of exercise just doesn’t work for them.

In a study last year in PLOS One, researchers asked people to try two different three-week training regimens, separated by several months.

Overall, people gained from both workouts. But the experience of each person varied — some nonresponders didn’t benefit from one of the workouts.

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However, the researchers found that no one failed to respond to both workouts.

So if you’re not getting the results you want, you might want to switch up your workout. If you’ve been doing cardio, try interval training, and vice versa.

This could also help you stay motivated.

Costello is a fan of variety in workouts and said that this can help people avoid getting stuck. This may include playing sports for fun or incorporating “sport-specific training as motivation in your workouts.”

Minardi suggests that people try activities with a social component.

“It’s human nature,” he said. “We have this desire to connect to other people, not just to exercise. And it’s great to combine both, which will enhance your consistency.”

Read more: Diversify your workout »

Working out smart

Both Costello and Turgiss recommend that exercise goals be specific, measurable, and realistic.

For someone just starting out, Costello might have them aim for 20 minutes of brisk walking three times a week, followed by five to 10 minutes of stretching, for four weeks.

Focusing on smaller time blocks like this — rather than the whole year — can help people succeed.

“Think about taking it in smaller chunks, like four weeks or six weeks,” said Turgiss. “Or if you really have a very hard time sticking with building a new habit like physical activity, break it down to two weeks.”

Once the habit of exercise is in place, you can add more to the workout to make it balanced — including cardio, strength training, and stretching.

After that, if you want you can turn it up a notch.

“Once a workout is balanced, start to add time and increase the intensity of each workout to continue to progress,” said Costello.

Although there is no “best” exercise program for everyone, working out efficiently — which sometimes means getting professional advice — can make all the difference.

“Anyone can train hard. Anyone can make a workout miserable,” said Minardi. “But is it smart? Big difference. Huge difference.”