These intriguing observations support the notion that the hamstrings probably should not be viewed in isolation of surrounding ipsilateral, and perhaps even contralateral, muscle groups.
Traditional thinking has been that mus-cle (hamstring and quadriceps) strength may be a predictor of risk for hamstring strains.
GAIT ANALYSIS INSIGHTS ON HAMSTRING MUSCLE FUNCTION Prior to an analysis of traditional risk factors for hamstring strains, a brief review of recent work detailing hamstring function during normal walking and running is presented in an effort to inform the reader of thoughts regarding muscle function that should likely be considered.
Gait analyses during running demonstrate that the hamstrings undergo a typical eccentric (muscle lengthening) contraction during the last 25% of the swing phase to assist in proximal hip extension while decelerating knee extension distally, opposing the quadriceps activity.
In fact, one study comparing functional rehab and core strengthening to traditional measures of hamstring strengthening and stretching showed that the former strategy was much more effective at secondary hamstring injury reduction.
However, the role of core strengthening and stability in primary hamstring injury prevention remains unknown at this point.With regards to hamstring flexibility and risk for injury, studies were reviewed by Prior et al and for the most part were not noted to show any clear association between flexibility and risk for hamstring strain.This may be due to a variety of factors, including non-standardised methods for assessment of muscle flexibility (sit-and-reach, straight leg raise) as well as the inability to isolate the hamstrings from likely high influential variables such as lumbo-pelvic control and pelvis range of motion.The same group used forward dynamic simulations to illustrate that although peak hamstring stretch was not affected by running speed, loading of the biceps femoris increased significantly with speed and was greater during swing than stance at the fastest speed.It was concluded that the large inertial loads observed during high-speed running may make the hamstrings most susceptible to injury during the swing phase of gait.Accordingly, a better understanding of risk factors and mechanisms for injury are argued to be fundamental to any significant future inroads to injury treatment and prevention.This review summarises our current thinking on risk factors for both primary and recurrent hamstring strains and guides us to thoughts on how future research can help advance our efforts to reduce these injuries at all levels of competition and age.In conclusion, although it appears that age may be a primary risk factor, careful analysis of potential confounding variables such as flexibility and body weight could provide new insights around this important topic.FLEXIBILITY AND STRENGTH Associations with strength and flexibility and risk for hamstring injury have been conflicting.A previous hamstring injury was the major risk factor for subsequent injury (hazard ratio 1.40; 95% CI, 1.12 to 1.75).Surprisingly, age was not a predictor of hamstring injury, perhaps due to the age and level of play of these individuals.