Introduction:
Hamstring strain injuries (HSIs) are prevalent among athletes and are detrimental to sports performance.

Aim of the study:
This study aims to compare two different rehabilitation protocols for managing pain, functional abilities, and muscular strength after HSIs.

Material and methods:
Fortyfive participants with acute hamstring strain were randomly allocated to three rehabilitation protocols. The first group performed baseline treatment (BT), consisting of 30 minutes of interferential therapy and manual therapy (i.e., an ice pack, myofascial release, and hamstring isometric exercises), and was considered a control group. The second group performed BT and a progressive agility and trunk stabilization (PATS) protocol. The third group performed BT and Russian current stimulation and a criteria-based rehabilitation program (CBRP). All participants were treated five consecutive days a week for three weeks. Pre- and post-treatment data was collected for pain (Numerical Pain Rating Scale [NPRS]), functional assessment (Functional Assessment Scale for Acute Hamstring Injuries [FASH]), and maximal isometric strength of hamstring muscles.

Results:
All three groups showed significant within-group improvements in all dependent variables (all p ≤ 0.001). When the three groups were compared, a significant difference was observed, favoring superior improvements in both experimental groups compared to the control group. In addition, when the experimental groups were compared, a significantly greater improvement in all dependent variables was observed in the CBRP compared to PATS.

Conclusions:
In conclusion, the findings of the study suggest that there is a significant difference between the rehabilitation protocols in managing hamstring injuries, with a greater improvement observed after the criteria-based rehabilitation program.