Hamstring strength and flexibility after hamstring strain injury: a systematic review and meta-analysis

Area of Science:

• Sports Medicine
• Rehabilitation Science
• Biomechanics

Background:

• Hamstring strain injuries are common in athletes, impacting performance and leading to re-injury.
• Understanding the long-term effects of hamstring injuries on strength and flexibility is crucial for effective rehabilitation.

Purpose of the Study:

• To systematically review and meta-analyze evidence on hamstring strength and flexibility following injury.
• To identify persistent deficits and inform rehabilitation and return-to-play protocols.

Main Methods:

• Systematic literature search of multiple databases (PubMed, CINAHL, SPORTDiscus, etc.) up to August 2015.
• Inclusion of full-text English articles assessing hamstring strength or flexibility in individuals with prior hamstring strain injury within 24 months.
• Meta-analysis of data from 28 included studies.

Main Results:

• Acute deficits in isometric strength (<7 days) and passive straight leg raise flexibility (<50 days) were observed.
• Persistent deficits in isokinetic concentric and eccentric knee flexor strength were found after return to play.
• Reduced hamstring to quadriceps strength ratios persisted post-return to play, though inconsistently across measurement methods.

Conclusions:

• While acute strength and flexibility deficits resolve within 50 days, dynamic strength deficits (concentric, eccentric) and strength imbalances persist.
• Monitoring flexibility and isometric strength during rehabilitation is recommended.
• Dynamic strength assessment at and after return to play is essential for previously injured hamstrings.