LUNG-VOLUME SPECIFICITY OF INSPIRATORY MUSCLE TRAINING

We examined the extent to which training-related increases of inspirat ory muscle (IM) strength are limited to the lung volume (VL) at which the training occurs. IM strength training consisted of performing repe ated static maximum inspiratory maneuvers. Three groups of normal volu nteers performed these maneuvers at one of three lung volumes: residua l volume (RV), relaxation volume (Vrel), or Vrel plus one-half of insp iratory capacity (Vrel + 1/2IC). A control group did not train. We con structed maximal inspiratory pressure-VL curves before and after a 6-w k training period. For each group, we found that the greatest improvem ents in strength occurred at the volume at which the subjects trained and were significantly greater for those who trained at low (36% for R V and 26% for Vrel) than at high volumes (13% for Vrel + 1/2IC). Small er increments in strength were noted at volumes adjacent to the traini ng volume. The range of vital capacity (VC) over which strength was in creased was greater for those who trained at low (70% of VC) than at h igh VL (20% of VC). We conclude that the greatest improvements in IM s trength are specific to the VL at which training occurs. However, the increase in strength, as well as the range of volume over which streng th is increased, is greater for those who trained at the lower VL.