INCREASED BONE-MINERAL DENSITY AFTER PROLONGED ELECTRICALLY-INDUCED CYCLE TRAINING OF PARALYZED LIMBS IN SPINAL-CORD INJURED MAN

Spinal cord injured (SCI) individuals have a substantial loss of bone mass in the lower limbs, equaling approximately 50% of normal values i n the proximal tibia, and this has been associated with a high inciden ce of low impact fractures. To evaluate if this inactivity-associated condition in the SCI population can be reversed with prolonged physica l training, ten SCI individuals [ages 35.3 +/- 2.3 years (mean +/- sta ndard error [SE]); post injury time: 12.5 +/- 2.7 years, range 2-24 ye ars; level of lesion: C6-Th4; weight: 78 +/- 3.8 kg] performed 12 mont hs of Functional Electrical Stimulated (FES) upright cycling for 30 mi n per day, 3 days per week, followed by six months with only one weekl y training session. Bone mineral density (BMD) was determined before t raining and 12 and 18 months later. BMD was measured in the lumbar spi ne, the femoral neck, and the proximal tibia by dual energy absorptiom etry (DEXA, Nordland XR 26 MK1). Before training, BMD was in the proxi mal tibia (52%), as well as in the femoral neck, lower in SCI subjects than in controls of same age (P < 0.05). BMD of the lumbar spine did not differ between groups (P > 0.05). After 12 months of training, the BMD of the proximal tibia had increased 10%, from 0.49 +/- 0.04 to 0. 54 +/- 0.04 g/cm(2) (P < 0.05). After a further 6 months with reduced training, the BMD in the proximal tibia no longer differed from the BM D before training (P > 0.05). No changes were observed in the lumbar s pine or in the femoral neck in response to FES cycle training. It is c oncluded that in SCI, the loss of bone mass in the proximal tibia can be partially reversed by regular long-term FES cycle exercise. However , one exercise session per week is insufficient to maintain this incre ase.