The back of the upper legs is a problem area for many, but it can easily be toned.Here’s an exercise so simple you can do it at home or even in your hotel room when on vacation.Personal trainer Melissa Smith, of the Olympic Club, started out as a track athlete and so she’s always paid close attention to caring for and toning her hamstring muscles. For this week’s summer shape-up series, she recommends hamstring curls.Exercise: Hamstring curlsMuscles toned: hamstrings, gluteusMethod:For beginners1) Find a stable piece of furniture to rest your feet against2) Lie flat on your back, arms by your side, palms facing down3) Rest your feet on the edge of the bench (or other sturdy piece of furniture), knees bent4) Slowly raise your hips off the ground as high as you can squeezing the back of your legs5) Slowly release your hips down halfway6) Slowly raise your hips back high off the ground squeezing the back of your legs7) Repeat steps five and six, 15 or 20 timesMs Smith recommends you do this exercise three times a week. To see her demonstrate the technique, visit www.theroyalgazette.com.