But it's possible you haven't sprinted in ages. When muscular development is at a standstill, adding that "forgotten" or different exercise is exactly what will jump-start new growth. When combined with a well-rounded lifting routine, two days of sprinting each week will lead to rapid growth in your hams and take your conditioning to new heights.

Incline Treadmill Sprints

A simple way to get started is incline treadmill sprints. The incline decreases the footfall when sprinting, which decreases joint stress and prevents you from over-striding and pulling a hamstring.

Try this routine twice per week either after lifting, or ideally, as a separate workout. After you warm-up and do some speed drills, sprint 10 seconds on, 50 seconds off. Go for 10 minutes. Then week by week increase your sprint time by one second and decrease the rest period by one second. Work your way up to 15-second sprints.

• Week 1: Sprint 10 seconds, rest 50
• Week 2: Sprint 11 seconds, rest 49
• Week 3: Sprint 12 seconds, rest 48
• Week 4: Sprint 13 seconds, rest 47
• Week 5: Sprint 14 seconds, rest 46
• Week 6: Sprint 15 seconds, rest 45

In time, this will add athleticism and size to your hamstrings, and it'll take care of that conditioning you've been skipping.