You've probably seen it on social media: 75 Hard. 75 Soft. 75 days to change your habits, get in shape and become a healthier version of yourself.

The idea is simple — commit to a set of healthy habits every day for 75 days. But the rules can be challenging, and jumping into a demanding exercise routine without a plan can sometimes do more harm than good.

So, before you lace up your sneakers and start counting down Day 1, what should you know?

Thomas J. Wallace, DO, with Lexington Family Practice White Knoll, says the biggest benefit of these challenges may be the structure they provide.

"I think that these challenges are appealing to people because they provide structure and a framework to make meaningful changes in their lives that have proven to bring results," Dr. Wallace says. "These challenges are not just geared towards fitness, but improving mental health and overall well-being."

While versions of the challenges can vary, 75 Hard is the more demanding of the two. The commonly followed program includes:

75 Soft takes a more flexible approach. There isn't one official version, but popular versions generally include:

The flexibility of 75 Soft may make it easier to incorporate into everyday life. At the same time, the stricter rules of 75 Hard may appeal to people who enjoy having clearly defined goals and accountability.

The name 75 Hard might make you think the challenge is only for people who already spend hours in the gym. That's not necessarily the case.

"You do not already need to be fit to consider the 75 Hard Challenge," Dr. Wallace says. "It does not mean you have to run for 45 minutes straight or power-lift 500 pounds. Your two exercises could be two 45-minute walks."

The key is choosing activities appropriate for your current fitness level—and building up gradually if you're new to exercise.

The potential benefits go beyond losing weight or getting stronger.

Regular physical activity can improve fitness and may help people manage certain chronic health conditions. Establishing healthy routines can also boost confidence and provide a sense of accomplishment.

"By completing these challenges, people improve their physical fitness, which in turn can help with chronic medical conditions, develop new habits that improve their mental self-image, and give a sense of accomplishment that can lead to further successes in life," Dr. Wallace says.

And there's something powerful about having a goal that gives you a reason to show up every day.

There's a potential downside to the enthusiasm surrounding these challenges: doing too much, too soon.

If you're currently walking a few times a week, suddenly jumping into two 45-minute workouts every day could put you at risk for injury.

"When starting a new exercise program or challenge, it can be very easy to get excited about it and overexert yourself, which can lead to injury," Dr. Wallace says.

His advice? Ease into it. He recommends increasing your exercise routine gradually rather than making a dramatic jump in activity.

And don't ignore persistent pain. If aches or pains don't go away or keep getting worse, talk with your doctor.

There isn't a one-size-fits-all answer.

“I would not recommend one challenge over the other," Dr. Wallace says. "I think each one has pros and cons that each person would need to evaluate based upon the changes they are looking for in their life and pick one based upon that."

Think about what you actually want to accomplish over the next 75 days.

Maybe you want to:

Once you know your goal, you can decide how much structure and challenge makes sense for you.

"People should determine what goals they want to accomplish over these 75 days, whether that be physical, mental or emotional," Dr. Wallace says. "Once you have targets you want to reach, completing the full 75 days may be more attainable."

A new fitness challenge can be a great opportunity to become more active, but it's worth making sure your plan is safe — particularly if you're new to exercise or have a chronic health condition.

Dr. Wallace recommends talking with your doctor before starting either challenge. Your doctor can help you determine whether the activities you're planning are appropriate and how you might modify them.

And know when to stop. Severe headache, chest pain, difficulty breathing or passing out are signs that require immediate medical attention.

The real goal isn't necessarily to complete a challenge perfectly. It's to create habits that stick.

“These challenges are designed to make meaningful and lasting changes in your lives," Dr. Wallace says. You don't have to transform your entire life overnight. A daily walk, a healthier meal, a few minutes of reading or a new hobby can all be steps toward better health.

"I encourage readers to take things at their own pace and not be discouraged," Dr. Wallace says. "Any physical fitness and movement can be healthy and impactful toward the next step forward."

So, whether you choose 75 Hard, 75 Soft or create your own 75-day challenge, focus less on perfection and more on building healthy habits you can keep long after Day 75.

Thomas J. Wallace, DO, Lexington Family Practice White Knoll