This is an excerpt from Complete Conditioning for Football by Aaron Wellman.
Hamstring injuries are also very common in football and are typically associated with high-speed sprinting or high-intensity deceleration actions in practice and games. Hamstring injuries will not prevent a player from training with the team, but they will necessitate modifications be made. For example, if the athlete has suffered a hamstring strain near the hip, squatting will become more difficult due to the lengthening of the hamstrings when shifting the hips back at the start of the descent of the squat. However, if the strain is more distal toward the insertion at the knee, the athlete has a much better chance of squatting without pain because of the limited activation of the hamstrings around the knee when squatting into deep knee flexion.
To train the hamstring directly, exercises like the barbell Romanian deadlift can be substituted with a less-intense hip hinge exercise like the 45- or 90-degree back extension. Figure 10.27 illustrates the 45-degree version of the back extension exercise. Back extensions can serve as gentler ways to stimulate the hamstring in a hip extension movement pattern while controlling for intensity of load. Arguably the most commonly used exercise for training the hamstrings by flexing and extending at the knee is the partner Nordic hamstring curl. When an athlete is dealing with a hamstring issue, this exercise may be far too intense in the early stages of post-injury training. If the athlete cannot endure the high eccentric forces of a partner Nordic hamstring curl, the athlete can substitute a roller leg curl (as illustrated in figure 10.28) or stability ball leg curl. These variations bring the intensity down significantly and can allow the athlete to strengthen the knee flexion movement.