ABSTRACT
To examine the effect of blood flow on peripheral nerve function in adults with type 2 diabetes. Ten adults with type 2 diabetes and 10 age- and body mass index-matched controls participated in the study. Soleus H-reflex and motor recruitment curves were determined for subjects at baseline, during 10 minutes of ischemia by femoral artery occlusion, and after a 10-minute bout of leg exercise. At baseline, the H-reflex threshold occurred at 77.44% +/- 1.12% and 92.23% +/- 0.04% (mean +/- SE) of motor threshold at baseline for the diabetes and control groups, respectively. During ischemia, the H-reflex threshold occurred at 72.44% +/- 7.19% and 88.79% +/- 7.80% of motor threshold at baseline for the diabetic and control groups, respectively. Following exercise, the H-reflex threshold occurred at 64.44% +/- 8.47% and 94.93% +/- 4.30% of motor threshold at baseline for the diabetes and control groups, respectively, which significantly differed from baseline. Hmax/Mmax ratios were significantly reduced with acute ischemia for the diabetes group (25.6%). Postexercise, the Hmax/Mmax ratio returned to baseline for controls while remaining significantly lower than baseline in the diabetes group. H-reflex and motor responses were hypoexcitable with an accompanying hyperemia for controls. In the diabetes group, the postexercise period resulted in a hyperexcitable H-reflex and motor response. Acute ischemia decreases H-reflex thresholds in adults with diabetes and exercise-induced increases in blood flow further decrease these thresholds. These responses are markedly more pronounced than those of their peers without diabetes and are accompanied by changes in sensory transmission to the motoneuron.
Subject(s)
Blood Flow Velocity , Diabetes Mellitus, Type 2/physiopathology , H-Reflex , Recruitment, Neurophysiological , Adult , Aged , Female , Humans , Male , Middle AgedABSTRACT
The authors examined the effect of acute ischemia on peripheral nerve function in healthy subjects. It was hypothesized that acute ischemia would interfere with the ability of sensory and motor nerves to propagate an impulse. Twelve young, apparently healthy adults participated in the study. Soleus H-reflex and motor recruitment curves were determined for subjects during a control condition, after 5 minutes of ischemia by femoral artery occlusion, and after a 5-minute recovery. During ischemia, the stimulus intensity required to evoke an H-reflex or M-wave was reduced by 18.3% and 18.4%, respectively. Hmax/Mmax ratios were significantly reduced with acute ischemia (mean +/- standard error) 66.29% +/- 5.4% and 58.81% +/- 6.7% for control and ischemia, respectively, owing to a decrease in Hmax during acute ischemia with no change in Mmax. After ischemia, the Hmax/Mmax returned to control values, as did the M-threshold. However, although the H-threshold slightly recovered, it failed to return to control threshold after 5 minutes of recovery. The results suggest that acute ischemia decreases motor and H-reflex thresholds in healthy individuals with a longer lasting effect for the H-reflex. In addition, a decrease in Hmax/Mmax ratio was observed, suggesting that acute ischemia has differential effects on sensory nerve propagation and synapse transmission.
Subject(s)
H-Reflex/physiology , Ischemia/physiopathology , Motor Activity/physiology , Sensory Thresholds/physiology , Acute Disease , Adult , Electric Stimulation/methods , Electromyography/methods , Evoked Potentials, Motor/physiology , Evoked Potentials, Motor/radiation effects , Female , H-Reflex/drug effects , Humans , Male , Motor Activity/radiation effects , Muscle, Skeletal/physiopathology , Muscle, Skeletal/radiation effects , Recruitment, Neurophysiological/physiology , Recruitment, Neurophysiological/radiation effects , Sensory Thresholds/radiation effects , Synaptic Transmission/physiology , Synaptic Transmission/radiation effectsABSTRACT
OBJECTIVES: The reproducibility of blood pressure variables from ambulatory blood pressure monitoring (AMBP) initiated at the same time of day (SAME: 1700-1900 h) was compared with the reproducibility of blood pressure variables when monitoring was initiated at opposite times of day (OPP: randomized, morning=0700-0900 h and evening=1700-1900 h). It was hypothesized that the reproducibility for SAME (n=18) would be no different than the reproducibility for OPP (n=13). METHODS: The order of AMBP sessions was randomized. The Accutracker II was used to determine average blood pressures, Crest (CrBP), Trough (TrBP), and TrBP : CrBP ratio; Averages were divided into 24-h, daytime (0600-2200 h), and night-time (2200-0600 h) for both systolic and diastolic blood pressures. A paired t-test with an intraclass correlation was used to determine the reproducibility of AMBP for both SAME and OPP. A chi-square was used to compare the distribution of reproducible AMBP variables between SAME and OPP. Significance was at P<0.05. RESULTS: The reproducibility of AMBP variables for SAME and OPP was a significantly different for systolic blood pressure. All of the ambulatory systolic variables measured in the SAME group were reproducible except for the TrBP : CrBP, whereas only the systolic night-time averages of the OPP group were reproducible. Similarly all of the ambulatory diastolic variables measured in the SAME group were reproducible except for TrBP : CrBP, whereas 24-h, night-time averages, and TrBP were reproducible in the OPP group. CONCLUSIONS: Ambulatory blood pressure variables were consistently higher when the monitoring session began in the morning hours.
