Biomedical subjects

P B Sanjabi

Publications and source records attributed to P B Sanjabi.

4 recordsLinked to original sources

PubMed1998

Identifying the integrated electromyographic threshold using different muscles during incremental cycling exercise.

BACKGROUND: The purpose of this study was to identify the IEMG threshold in the vastus lateralis (VL) and rectus femoris (RF) muscles during progressive, incremental exercise and to relate these thresholds to the ventilatory threshold (Tvent). METHODS: Ten men (age: 23.40 +/- 3.13 yrs, mass 76.64 +/- 8.13 kg, % fat: 8.81 +/- 2.32, VO2peak: 66.37 +/- 10.61 ml.kg.min-1) with cycling experience completed a graded exercise test on a cycle ergometer by cycling at 90 rpm using 45 watt increments at two minute intervals. Oxygen uptake was measured continuously and the IEMG activity of the VL and RF was calculated during the last 5 s of each minute. The mean for the IEMG of 6 to 7 complete pedal revolutions was used as the final value. Tvent was visually identified using the VE/VO2 and V-slope methods. The IEMG threshold for VL and RF was visually identified at the inflection point where a non-linear increase in IEMG occurred. Comparisons between Tvent and IEMG thresholds were made using dependent means "t"-tests. RESULTS: Results showed that an IEMG threshold was identified in all 10 subjects for the RF, but in only 5 of 10 subjects for the VL. However, when identified, the IEMG threshold for VL was similar to RF.VO2 at IEMG threshold for RF (3.53 +/- 0.36 L.min-1) was not significantly different from Tvent (3.36 +/- 0.42 L.min-1). CONCLUSIONS: These results show that the IEMG threshold is more consistently detected in the RF compared to VL during incremental cycling exercise. In addition, the IEMG threshold for RF was closely related to Tvent and provides an alternative means to assess the ventilatory threshold.

Adult↗

PubMed1997

The effect of exercise induced glycogen depletion on the lactate, ventilatory and electromyographic thresholds.

BACKGROUND: This study compared the integrated electromyogram (IEMG), lactate, and ventilatory thresholds under normal glycogen (NG) and depleted glycogen (DG) conditions for the purpose of determining the presence of a possible relationship between neuromuscular, metabolic and respiratory thresholds. MATERIALS AND METHODS: Six trained, male cyclists (Age = 24.0 +/- 2.45 yrs, Ht = 1.76 +/- 0.84 m, Mass = 76.22 +/- 10.03 kg, % Fat = 8.57 +/- 1.50, VO2 peak = 68.97 +/- 10.46 ml . kg-1 . min-1) completed a progressive, incremental cycle ergometer test under NG and DG conditions in a randomized order. Glycogen depletion was accomplished by having the subjects: (1) engage in a 12 hour fast prior to the exercise test, (2) complete a 1.5 hour ride at their ventilatory threshold, and (3) complete 4 to 8 one-minute rides at 100% of VO2 peak. Six hours following the depletion rides, the subjects completed the exercise test (90 rpm, 45 watts/2 min). Blood was withdrawn through a forearm venous catheter each minute and later analyzed for blood lactate. Metabolic data were measured every 30s and the IEMG of the rectus femoris was recorded during the last 10s of each minute of the exercise test. Results showed that under NG, the IEMG (TIEMG), lactate (Tlac), and ventilatory (Tvent) thresholds occurred at a similar VO2 (TIEMG = 3.46 +/- 0.31, Tlac = 3.51 +/- 0.34, Tvent = 3.36 +/- 0.42 L . min-1). However, under DG there was a significant shift in the TIEMG to a higher VO2 (TIEMG = 4.41 +/- 0.54 L . min-1 = p 0.003). Tlac was not significantly greater following glycogen depletion, but had shifted to a higher VO2 in relation to the Tvent (Tlac = 3.96 +/- 0.40 L . min-1, Tvent = 3.37 +/- 0.64 L . min-1 = p 0.01). These data show that lactate accumulation and muscle activation of the vastus lateralis and rectus femoris are not the controlling mechanisms of the ventilatory threshold during progressive, incremental cycling exercise.

3-Hydroxybutyric Acid↗

PubMed1993

Re-examination of the incidence of exercise-induced hypoxaemia in highly trained subjects.

The purpose of this study was to examine the occurrence of exercise-induced hypoxaemia (EIH) during maximal exercise in highly trained athletes. Eleven trained cyclists (mean(s.d.) age 23(3.5) years; mean(s.d.) VO2max 66.9(4.8) ml kg-1min-1) performed a continuous, multistage (270 kpm min-1) cycle ergometer test to exhaustion. Measurements of arterial oxygen-haemoglobin saturation (%HbO2) were obtained simultaneously at rest, every 2 min during exercise, and at maximum exercise capacity from arterial blood sampling (%SaO2) and ear oximetry (%SpO2). Exercise induced hypoxaemia (%HbO2 < or = 91%) was present in 64% of the athletes examined when EIH was determined using pulse oximetry, whereas none of the subjects exhibited EIH when %HbO2 was determined using arterial blood. At rest the values for %HbO2 were similar with mean(s.d.) %SaO2 being 97.3(0.6)% and mean(s.d.) %SpO2 being 96.5(1.6)%. During exercise, statistically significant differences were found for %HbO2 between arterial blood and ear oximetry at the 6-min, 8-min, and maximal exercise sampling times (repeated measures analysis of variance, P < 0.05). The results indicate that ear oximetry overestimates the incidence of EIH and underestimates the oxyhaemoglobin saturation in highly trained cyclists during exercise in comparison with those measurements made from arterial blood.

Adult↗

PubMed1991

Effect of caffeine ingestion on alveolar ventilation during moderate exercise.

The purpose of this study was to examine the effect of caffeine ingestion on alveolar ventilation and physiological dead space ventilation during exercise in high and low caffeine users. Eleven males (mean age 26.4 +/- 5.4 years), classified as either high caffeine users (greater than 350 mg/d, n = 6) or low caffeine users (less than 50 mg/d, n = 5) performed two treadmill exercise conditions at a constant work rate (50% VO2max) 45 min after ingestion of 3.3 mg of caffeine/kg body weight or placebo using a double-blind protocol. Open circuit spirometry was used to determine ventilatory and gas exchange variables every 10 min during the 50 min of walking exercise. Analysis of variance showed that caffeine produced significant differences in alveolar ventilation (VA) and the physiological dead space ventilation/tidal volume ratio (VD/VT) with VA increased from 1.36 to 1.54 L/breath and VD/VT decreased from 22.3 to 20.5% between the placebo and caffeine treatments, respectively. Additionally, caffeine ingestion produced a significant increase in tidal volume (VT) and a significant decrease in frequency of breathing (fb). We conclude that caffeine consumed prior to exercise enhances ventilatory dynamics during exercise without regard to prior habitual caffeine consumption.

Adult↗