In this cross-sectional study, normal subjects (41 males) were compared to patients with lumbar disc herniations (L4-L5 and/or L5-S1; 25 males) in trunk strength and knee strength.  None of the subjects in both groups were involved in an exercise program six months prior to the study.  Leg strength was determined with seated bilateral and unilateral knee joint flexion and extension at two speeds of movement (60 and 120 degrees per second).  Trunk strength was determined with seated trunk flexion and extension at two speeds of movement (60 and 120 degrees per second). 

It was discovered that patients with lumbar disc herniations had muscle strength of the trunk and knees which had decreased to a similar extent (30% vs. 29%), independent of speed of movement.  A second finding was the control group (normal subjects) was significantly stronger in unilateral leg strength than the patients group (patients with lumbar disc herniations).  A third finding was unilateral leg strength was similar in the patients group in the leg with sciatica and the leg without sciatica, independent of lumbar disc herniation location.  Thus lower level disc (L4-L5 and/or L5-S1) herniation with nerve root compression or sciatica did not have an effect on knee strength (L2-L4 nerve roots).

Researchers hypothesis that the decrease in muscle strength could be due to muscle atrophy and/or pain-related fear of movement.

So what?  This study creates more questions than answers.  It shows us that seated trunk flexion / extension and bilateral / unilateral knee flexion / extension strength are affected by lumbar disc herniations in in-active males ranging from 20 to 37.  More research needs to be done on what can be done to return strength to normal levels and if doing so helps in the recovery of patients with lumbar disc herniations.

For full details of the study:  Ho CW, Chen LC, Hsu HH, Chiang SL, Li MH, Jiang SH, Tsai KC.  Isokinetic muscle strength of the trunk and bilateral knees in young subjects with lumbar disc herniation.  Spine. 2005 Sep 15;30(18):E528-33. 

Article written by Rick Kaselj - rkaselj@healingthroughmovement.com

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