SHORT-TERM EFFECTS OF BRACING ON EXERCISE PERFORMANCE IN MILD IDIOPATHIC THORACIC SCOLIOSIS

In adolescent idiopathic thoracic scoliosis (ITS) working capacity may be reduced during exercise. Despite concern about its usefulness, bra cing is still being used in ITS. Thus the effects of bracing on exerci se performance need to be examined. We studied six females, ages 12-15 years who had mild ITS (Cobb angle range 20-35 degrees). Pulmonary vo lumes, maximal voluntary ventilation (MVV), breathing pattern, the low est (most negative in sign) pleural pressure during sniff maneuver (Pp l(sn)), and pleural pressure swings (Ppl(sw)) were measured first. The n, Ppl(sw), O-2 uptake ((V) over dotO(2)) CO2 output ((V) over dotCO(2 )), heart rate (HR) at rest and during progressive incremental exercis e on a cycling ergometer (10 watts/min) were recorded. The exercise te st was performed under control conditions without bracing: (C) and aft er 7 days of bracing with the brace on (B). Dyspnea was measured by a modified Borg scale. At rest, bracing mildly affected total lung capac ity and forced vital capacity (p < 0.03 for both) but not breathing pa ttern, Ppl(sn), or Ppl(sw)(%Ppl(sn)), a measure of respiratory effort, Furthermore, bracing did not consistently affect maximum work rate (W Rmax). In both B and C (V) over dotO(2) was below (<70%) the predicted value, (V) over dotE was below (<45%) MVV, and HR reserve was <15 bea ts/min, indicating some cardiovascular deconditioning. On the other ha nd, respiratory frequency (Rf) increased more in B than in C (p < 0.03 ). In addition, Ppl(sw), Ppl(sw)(%Ppl(sn)), and Ppl(sw)(%Pplsn)/VT, an index of neuroventilatory dissociation (NVD) of the respiratory pump, were greater in B (p < 0.03 for all). At a similar work rate, the Bor g rating score was greater with bracing on than off, and the differenc e. (Delta Borg) tended to relate to concurrent changes in Ppl(sw)(%Ppl (sn))/VT (r(2) = 0.71; p < 0.07). We conclude that bracing affects res piratory effort, NVD, and dyspnea score during progressive exercise. T hese effects are consistent with increased lung elastance. Diminished exercise tolerance in patients with mild ITS probably reflects impaire d physical fitness but is not affected by bracing. Training programs p roposed for this subset of patients to increase peripheral muscle perf ormance might also consider NVD of the respiratory pump.