An acute bout of body-weight support treadmill training improves blood glucose control in obese men with incomplete spinal cord injuries: A case series
1Maher J, 1Nash M, 2Mendez A
1The Miami Project to Cure Paralysis, Miami, FL, USA; 2The Diabetes Research Institute, Miami, FL, USA
Objective: Investigations that report the use of bodyweight support treadmill training (BWSTT) in persons with SCI have yet to address potential benefits of the activity on cardioendocrine complications of insulin resistance (IR) and obesity. This study examined intensity-dependent metabolic responses and adaptations of blood glucose control during and following BWSTT in obese individuals with incomplete SCI (iSCI).
Methods: Case participants were three males aged 38-51 years with chronic (2-13 years) iSCI at C3-5. Participants performed graded arm exercise tests to establish peak O2 consumption (VO2), and on a different day underwent a ‘baseline’ 75-gram oral glucose tolerance test (OGTT). Participants were allowed 2-3 sessions of BWSTT to familiarize themselves with the testing procedures and were unweighted during stepping by 34-61% of their body mass, the minimum necessary to maintain acceptable stepping form. On the day of testing, participants underwent a continuous 45-minute bout of BWSTT following an overnight fast. Respiratory gases were collected throughout the bout and averaged to compute exercise intensity relative to their peak values. The OGTT was repeated following BWSTT, with venous insulin and glucose measured via automated methods.
Results: All participants had major risks for obesity (BMI = 26.8-35.1 kg/m2) and insulin resistance per the Homeostatic Model-2 (HOMA2-IR) Assessment (HOMA-IR = 3.2-4.7). Mean VO2 during BWSTT was below the conventional intensity threshold for cardiorespiratory conditioning (40%) in two participants (33 and 36%), but was greater than this criterion in the other (56%). Immediate post-BWSTT OGTT showed insulin concentrations before glucose challenge at 82%, 69%, and 7% lower than observed during ‘baseline’ testing performed on a day without BWSTT. Peak post-load insulin concentrations were also lower across all post-load timepoints than observed during ‘baseline’ testing, although none of these time points were different concerning glucose concentration. The HOMA2 was lowered following BWSTT by 72 and 68% of two participants and unchanged in the third.
Conclusion: Lower pre-load insulin concentration and peak insulin values observed following BWSTT suggests the activity decreases the concentration of insulin required to dispose of the same glucose load. In two of three subjects, BWSTT lowered insulin resistance proxy values for HOMA2-IR from a baseline score that denotes insulin resistance (>2.25) to levels within the normal range as recommended by the American Heart Association. The duration of these changes was not tested. The two participants who saw the greatest improvements use power wheelchairs and thus experience limited non-exercise physical activity, as opposed to the third participant who uses a manual chair and can also ambulate with assistance. These findings suggest that BWSTT, even when performed below 40% of VO2peak, can be sufficiently intense to transitionally improve insulin resistance and lower plasma insulin concentration, especially in those individuals who are more sedentary and perform less physical activity throughout daily life. The duration of this benefit requires testing.
Support: Funded by The Miami Project to Cure Paralysis.
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