Temporal coupling of respiratory and locomotor patterns may provide a neuromechanical advantage to breathing. Following incomplete spinal cord injury (ISCI), supraspinal input to spinal motoneurons is disrupted. Propriospinal pathways, however, often remain intact after ISCI and respiration and locomotion may remain neurologically coupled. Coupling of these motor behaviors in human ISCI has not been extensively examined. Additionally, limited information exists about the effect of rehabilitation on locomotor-respiratory coupling (LRC). The purpose of this pilot study was to examine LRC during walking after ISCI. The extent of LRC was quantified using a stride-by-stride method to assess coordination between walking and breathing rhythms. Additionally, the effects of three weeks of locomotor training on LRC were examined.
Two adults with chronic ISCI were assessed during over ground and treadmill walking. Subjects were evaluated before and after 15 sessions of locomotor training with manual assistance and partial body-weight support. Stride cycles during walking were measured based on the onset of left quadriceps activation. Respiratory timing was determined with a flow thermistor, with inspirations defined as peaks of the flow thermistor trace. The coupling interval, the percent time of each stride cycle at which the first inspiration of that cycle occurred, was calculated. Adapting a previously published method (Hill et. al., 1988), breaths were considered coordinated if the coupling interval was the same +/- 9% for at least 4 inspirations in a row. Percent coordination (%COORD) was determined as the percentage of total first inspirations in each stride cycle which were coordinated.
One subject (C6, AIS D) demonstrated no coordination, before or after locomotor training, in either the over ground or treadmill conditions. The other subject (L2, AIS C) demonstrated a decrease in %COORD over ground after training (pre-training, 73%; post-training, 43%), while demonstrating an increase in %COORD during treadmill walking after training (pre-training, 0%; post-training, 35%).
These data are consistent with previous evidence that LRC can occur after ISCI in humans, and suggest that LRC may be altered by rehabilitation. Future research must consider the speed and amount of time subjects walk during evaluations, as coupling may not occur during short walking bouts or at low speeds as was seen in one subject. Injury level and severity may also affect LRC, and warrants further investigation. Determining functional implications of the effects of rehabilitation on LRC requires additional examination.
Authors: *T. SUTOR1,2, N. J. TESTER1,3, D. FULLER1, K.-A. STREETER1, K. A. BUTERA1,2,3, E. J. FOX1,2,3;
1Univ. of Florida, Gainesville, FL; 2Brooks Rehabil., Jacksonville, FL; 3Malcom Randall V.A. Med. Ctr., Gainesville, FL
Disclosures: T. Sutor: None. N.J. Tester: None. D. Fuller: None. K. Streeter: None. K.A. Butera: None. E.J. Fox: None.