You hit the gym day after day, becoming lean and powerful. But you come home to find the love of your life sprawled in front of the TV every time with a bowl of potato chips.

Even some personal trainers say getting your partner to work out can be harder than bench pressing 500 pounds.

“I have been able to get my hubs to eat healthier, but the fitness thing just hasn’t truly clicked,” said one. “I even even did P90X with him!”

On one hand, success could bring huge rewards. You could do more together. Your sex life could get hotter. Someone you love could live a longer, healthier life.

On the other hand, anything you say could sound like an insult. Pity the fool who bought his girlfriend a scale.

Studies Show You Can Get Your Partner to Work Out

So let’s start with the good news. Two new studies this month suggest that you truly can get your partner to work out.

One study, presented at a meeting of the American Heart Association, showed that men whose wives become more active are 70 percent more likely to become more active than men whose wives stay sedentary.

(A husband who becomes active only boosts his wife’s likelihood of activity by 40 percent. But one of the researchers, Laura Cobb of Johns Hopkins University, told me the difference was not statistically significant. “So we can’t really say that wives influence husbands more.”)

The study did show the influence goes both ways. Cobb and her colleagues found that having a spouse who becomes less active also increases your likelihood of becoming less active.

Of course the study doesn’t prove you can change your significant other. There are other explanations for her findings, Cobb admitted. People tend to marry people like themselves. And couples live in similar environments. Husband and wife might both be inspired by a nice jogging trail nearby.

But Cobb likes to think that you really can get your partner to work out. And that was the conclusion of the other study, published in the Journal of the American Medical Association: Internal Medicine.

Researchers from University College London found that being in a relationship with a someone who is already fit is less important than being in a relationship with someone who becomes fit after the relationship starts.

That leads me to my first tip:

1) Set an Example

Even if you’re fit already, take on a new inspiring challenge. Rather than nagging, talk about how much fun you’re having. “I feel so great now that I can run a marathon.”

2) Praise your partner’s fitness accomplishments.

“You look so sexy when you glisten!”

3) Provide support:

“You said you wanted to go for a walk today. Why don’t I do the shopping?”

4) Do It Together

When I surveyed personal trainers, the ones who hadn’t thrown up their hands all had the same idea:

“Find an activity of mutual interest to both of you,” recommends Mike Connors of the American Physical Therapy Association.

Jamie Walker, cofounder of SweatGuru, agreed: “You’ll look forward to it and it won’t feel like nagging.”

The key here is to make sure it’s something you both truly like doing. Taking your husband to P90X classes for his sake is a little like going to church for your kids’ sake. They can tell what you really feel.

Nicole Crane, a health coach at Foodie Love Fitness, found that she and her husband enjoy a lot of activities:

Fitness day dates that my spouse and I sometimes do include hiking, mountain biking and playing tennis. Working out together is a way to do something healthy for your body AND spend some quality time with your partner.

So perhaps getting your partner to work out doesn’t have to feel like heavy lifting.

Photo: Nicole Crane and her husband enjoyed a bicycling trip in Austria together.

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