The diaphragm and abdominal muscles can be recruited during non-respiratory maneuvers. With these maneuvers, transdiaphragmatic pressures are elevated to levels that could potentially provide a strength-training stimulus. To determine if repeated forceful non-respiratory maneuvers strengthen the diaphragm, four healthy subjects performed sit-ups and biceps curls three-to-four days per week for 16 weeks and four subjects served as controls. The maximal transdiaphragmatic pressure was measured at baseline and following 16 weeks of training. Maximum static inspiratory and expiratory mouth pressures and diaphragm thickness derived from ultrasound were measured at baseline, 8, and 16 weeks. Following training, there were significant increases in diaphragm thickness (2.5 ± 0.1 to 3.2 ± 0.1 mm (mean ± SD) (p < 0.001)), maximal transdiaphragmatic pressure (198 ± 21 to 256 ± 23 cm H₂O (p < 0.02)), maximum static inspiratory pressure (134 ± 22 to 171 ± 16 cm H₂O (p < 0.002), maximum static expiratory pressure (195 ± 20 to 267 ± 40 cm H₂O (p < 0.002) and maximum gastric pressure (161 ± 5 to 212 ± 40 cm H₂O (p < 0.03)). These parameters were unchanged in the control group. We conclude that non-respiratory maneuvers can strengthen the inspiratory and expiratory muscles in healthy individuals. Since diaphragm thickness increased with training, the increase in maximal pressures is unlikely due to a learning effect.