Strengthening the core.
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Abdominal Muscles↗
Biomedical subjects
Jerrold Petrofsky
Publications and source records attributed to Jerrold Petrofsky.
Effects of electrical stimulation on skin blood flow in controls and in and around stage III and IV wounds in hairy and non hairy skin.
BACKGROUND: While wounds heal more quickly when electrical stimulation (ES) is applied, few studies have examined blood flow (BF) in and around wounds during ES in controls with no wounds compared to wounds in diabetic and non diabetic subjects. MATERIAL/METHODS: Ten subjects with stage III and IV wounds and 8 controls were subjected to 5 minutes of biphasic ES (20 milliamps, pulse width 250 usec). Before, during, and after, BF were measured by a Laser Doppler Imager. RESULTS: For the control subjects, in the fingers, BF increased from 307 flux to 687 after 5 min of ES to one finger but BF also increased to other fingers indicating a reflex increase in flow mediated by the sympathetic nervous system. For hairy skin, there was a 12% increase in BF with ES and only in the line directly between the stimulating electrodes. For the patients (either with or without Type 2 diabetes), stimulation in the hand, leg and foot all caused a large increase in BF during and for 5 minutes after stimulation. In patients, BF was high in the wound area before ES and increased by 53% during, and remained high after stimulation was over. CONCLUSIONS: The results show that in wounds, where BF is high due to bradykinin and cytokine release, the vasoconstrictor tone is not present and electrical stimulation causes a large increase in circulation which lasts after stimulation is over.
Aged↗
The effects of type 2 diabetes and aging on vascular endothelial and autonomic function.
BACKGROUND: Both endothelial cell function and autonomic function are influenced by age. However, the interrelationships between the 2 have not been carefully examined. MATERIAL/METHODS: Thirty nondiabetic control subjects (C) and 25 subjects with type 2 diabetes (D) participated. Endothelial cell function was assessed by 4 minutes of occlusion of the brachial artery followed by measurement of blood flow (BF) immediately post occlusion. To assess autonomic reactivity, subjects were exposed to a 32 degrees C room for 30 minutes and a tilt table elevated subjects from the horizontal to the 45 degree head up position. A laser Doppler flow imager was used to assess skin flows during the tilting phase. RESULTS: For endothelial function, the average BF of C increased 2.24+/-0.64 cc/100 gm tissue/minute at rest to 26.8+/-4.9 cc/100 gm tissue per minute post occlusion. D subjects had resting BF of 0.8 cc/100 gm tissue per minute with an increase to an average of 8.1+/-3.64 cc/100 gm tissue per minute post occlusion. In both, aging was associated with lower resting and post occlusion BF. However, D had lower BF than the controls. For D, both the resting flows and reduction in flows during tilting were less than the controls. Both groups followed a parallel decrease in flow with aging. Autonomic reactivity (ratio of BF to the skin in the vertical to horizontal posture) was 0.4+/-0.27 for the controls and 0.72+/-0.09 for the subjects with diabetes. CONCLUSIONS: The data suggests that diabetes alters both the endothelial and autonomic function.
Adult↗
Gait characteristics in patients with type 2 diabetes; improvement after administration of rosiglitazone.
BACKGROUND: Gait is impaired in people with type 2 diabetes. An insulin sensitizer, rosiglitazone(RSG) has promise to reverse some of the circulatory impairments seen in diabetes. The hypothesis to be tested was if RSG would improve gait in patients with diabetes. MATERIAL/METHODS: Gait in 30 controls and 25 subjects with Type 2 diabetes was examined (10 subjects with diabetes were placed on rosiglitazone (4 mg/day) for 6 months, a PPAR-gamma ligand known to improve peripheral circulation, to asses any improvements in gait). Gait was analyzed by video, shoe sensors, accelerometers and electromyogram of the medial gastrocnemius and tibialis anterior muscles during the initiation of gait, steady state gait and turns. RESULTS: Subjects with diabetes had almost double the movement at the knee in both the flexion-extension and lateral directions than did control subjects. For example, for flexion-extension at the knee during constant velocity gait in a linear path, subjects with diabetes averaged a force of 1.91+/-0.29 g whereas control subjects only averaged 1.26+/-0.27 g, these differences were significant (p<0.01). Subjects with diabetes also showed greater muscle use (the average use of the tibiallis anterior muscle was 26.5+/-6.9% of total muscle activity for control subjects whereas subjects with diabetes averaged 59.6+/-14.9%). CONCLUSIONS: These differences were reversed after 6 months administration of rosiglitazone. The results seem to imply that much of the impairment in gait is associated with cardiovascular insufficiency to the nervous system and/or muscle.
Adult↗
Effects of aging and type 2 diabetes on resting and post occlusive hyperemia of the forearm; the impact of rosiglitazone.
BACKGROUND: Both Diabetes and ageing are associated with reduced vascular endothelial function. The exact relationship between the 2 and any improvements from the insulin sensitizer rosiglitazone have not been explored. METHODS: Thirty controls and sixteen subjects with type 2 diabetes participated in a series of experiments to examine the interrelationships between age, diabetes and endothelial cell function. In subjects with diabetes, the insulin sensitizer rosiglitazone (RSG), a drug also known to improve vascular function, was administered for 3 months to see how it altered these relationships. Resting forearm flows (RF) and blood flows after 4 min of vascular occlusion (PF) were measured as an index of endothelial cell function. RESULTS: RF, measured by venous occlusion plethysmography, was negatively correlated to both age and diabetes. Administration of RSG for 3 months was associated with an increase in the blood flow response to venous occlusion so that it was not significantly different than that of age matched controls. Total PF in control subjects, compared to subjects with diabetes, averaged 56.58 +/- 12.57 and 13.6 +/- 8.01 cc/100 cc tissue per min respectively, and were significantly different (p < 0.01). After 3 months on RSG, differences between PF in the two groups were no longer evident. CONCLUSION: These studies suggest a different mechanism causing a reduction in vascular reactivity with aging and diabetes.
Journal Article↗
Muscle temperature and EMG amplitude and frequency during isometric exercise.
INTRODUCTION: While muscle temperature is known to vary with environmental temperature and the insulation provided by clothing, little has been published examining the interrelationships between the amplitude and frequency of the electromyogram (EMG), muscle tension, muscle fatigue, and muscle temperature. METHODS: Seven male subjects immersed their arms and legs in water at 24, 27, 34, and 37 degrees C for 20 min. Muscle temperature, strength (maximal voluntary contraction; MVC), endurance for a fatiguing contraction at 40% MVC, and EMG were assessed in the handgrip, biceps brachii, quadriceps, and gastrocnemius muscles. RESULTS: MVC was 44.8% lower for all muscles examined at the coldest muscle temperature. For all temperatures, the relationship between EMG amplitude and tension for brief isometric contractions was nearly linear; however, the increase in the amplitude of the EMG with muscle fatigue was reduced for the coldest muscle temperatures. The frequency components of the EMG and motor unit conduction velocity were largely unaffected by muscle tension but were inversely related to muscle temperature, with a 10 degrees C reduction in temperature resulting in a 32 Hz reduction in the center frequency. During fatiguing contractions at a tension of 40% MVC, the percent reduction in frequency was similar for all muscle temperatures, being reduced by about 20% from the beginning to the end of the contractions. DISCUSSION: EMG amplitude can be used to assess muscle use in most physiological conditions, but the frequency components of the EMG are so related to temperature as to make its use more restricted.
Adult↗
Gait characteristics in people with type 2 diabetes mellitus.
Sixteen control subjects and 15 subjects with type 2 diabetes were examined to compare gait characteristics during walking in a linear path and in turns of 0.33 and 0.66 m diameter. Subjects were excluded if there was diminished sensation in the feet or impairment of strength in the legs. This was done to isolate the effect of diabetes gait independent of loss of sensation. Gait was assessed through contact sensors on the foot, video, and two axis accelerometers mounted bilaterally on the head, shoulders, hips, knees and ankles. The results of these experiments showed that subjects with diabetes walked significantly slower (P<0.05) than control subjects and with a wider stance (P<0.01), both for walking in a linear path (velocity of subjects with diabetes was 62.2% that of controls and stance was 134.9% wider than controls) and when making turns (velocity 50.6% of controls and stance 120.1% wider than that of controls). Accelerometry showed increased flexion/extension and lateral movement of the major joints in subjects with diabetes during both walking in a linear path and turns compared to control subjects. Part of the increased movement at the joints in the subjects with diabetes was due to tremor in both the 8 Hz and 16 Hz bands. These findings suggest that at least some of the increased joint movement during walking in people with diabetes is likely neurological in origin and not related to muscle weakness or loss of sensation in the feet.
Adult↗