Background Asymptomatic musculoskeletal function, normal range of joint motion and normal muscle strength are considered not adequate star points to design a prevention injury program.

Objective To assess core muscle balance and control in the lumbar spine using simple functional tests during low load activity and high load dynamic movements.

Design Cross-sectional descriptive study.

Setting Professional road cyclists.

Patients 51 elite road cyclists were functionally evaluated at the beginning of the 2010 season. All injuries affecting racers during previous seasons were recorded throughout a clinical oriented interview.

Interventions Specific assessment of the site (lower back and pelvis) and direction of uncontrolled movement, under low and high loading within functionally orientated tasks.

Main outcome measurements Three tests were conducted in the crook laying position: (1) double leg lift and lower, (2) single leg extension, (3) bridge+single leg extension. In two first tests the ‘stabilizer’ pressure biofeedback unit was used to measure the influence of the global muscle system on trunk stability. Muscle functional extensibility of iliopsoas, tensor fasciae late, anterior rectus femoris and hamstrings were also evaluated.

Results Uncontrolled movements in lower back in low load test were found in flexion (57% of cyclist) and extension test (67%). Passive and active restriction of hamstrings while sitting showed significant correlation with impaired low back movements in flexion test (p<0.05). Weakness of the gluteus maximus correlated with uncontrolled movement in low back extension at high loading. Impaired movements in pelvic girdle (70%) showed a statistically significant relationship with asymmetrical passive restriction of rectus anterior muscle (p<0.03).

Conclusion Muscle imbalance between hamstrings and hip flexors together with weak hip extensors provoke uncontrolled movements in the low back of cyclists, predisposing them to more overuse injuries. A specific preventive program should be desirable.