RESUMEN
The Rockport Walk Test (RWT) is a 1-mile walk used to estimate the maximal volume of oxygen uptake (V(O2)max). The purpose of this study was to validate the RWT on a nonmotorized curved treadmill (CT). Twenty-three healthy adults (10 females; 19-44 years old) participated. One trial of the RWT was performed on a measured indoor track (RWTO) and another on the CT (RWTC) on different days in randomized order. Heart rate (HR) and completion time were used to calculate V(O2)max using 6 different general and gender specific equations from previous research. Subjects also performed a treadmill graded exercise test (GXT), which was used as the criterion measure for V(O2)max. Completion times and HR between the 2 RWT were compared using dependent t-tests. Estimated V(O2)max values were compared between the RWTC, RWTO, and GXT through repeated measures analysis of variance, Pearson's correlations (r), and Bland-Altman's plots. There was no difference between completion times for the RWTO and RWTC but HRs were significantly higher with RWTC. When the same equation was applied to the RWTO and RWTC, there were no similar results. All V(O2)max estimations were different from observed V(O2)max except for the estimation from the relative general Kline et al. equation on the RWTO. Despite high correlations (r = 0.75-0.91), the RWTC underestimated V(O2)max. The RWTC underestimates V(O2)max but may be beneficial if a new equation were created specifically for the CT. With appropriate equations for the CT, the RWTC would provide an alternate form of V(O2)max testing.
Asunto(s)
Prueba de Esfuerzo/instrumentación , Consumo de Oxígeno , Caminata/fisiología , Adulto , Prueba de Esfuerzo/métodos , Femenino , Frecuencia Cardíaca , Humanos , MasculinoRESUMEN
Hyperglycemia causes oxidative damage in tissues prone to complications in diabetes. Low-level light therapy (LLLT) in the red to near infrared range (630-1000nm) has been shown to accelerate diabetic wound healing. To test the hypothesis that LLLT would attenuate oxidative renal damage in Type I diabetic rats, male Wistar rats were made diabetic with streptozotocin (50mg/kg, ip), and then exposed to 670nm light at a dose of 9J/cm(2) once per day for 14weeks. The activity and expression of catalase and the activity of Na K-ATPase increased in kidneys of light-treated diabetic rats, whereas the activity and expression of glutathione peroxidase and the expression of Na K-ATPase were unchanged. LLLT lowered the values of serum BUN, serum creatinine, and BUN/creatinine ratio. In addition, LLLT augmented the activity and expression of cytochrome c oxidase, a primary photoacceptor molecule in the mitochondrial respiratory chain, and reduced the formation of the DNA adduct 8-hydroxy-2'-deoxyguanosine in kidney. LLLT improved renal function and antioxidant defense capabilities in the kidney of Type I diabetic rats. Thus, 670nm LLLT may be broadly applicable to the amelioration of renal complications induced by diabetes that disrupt antioxidant defense mechanisms.
Asunto(s)
Diabetes Mellitus Experimental/terapia , Riñón/enzimología , Fototerapia , Animales , Nitrógeno de la Urea Sanguínea , Catalasa/metabolismo , Creatina/sangre , Diabetes Mellitus Experimental/inducido químicamente , Diabetes Mellitus Experimental/enzimología , Glutatión Peroxidasa/metabolismo , Rayos Infrarrojos , Riñón/efectos de los fármacos , Riñón/efectos de la radiación , Masculino , Ratas , Ratas Wistar , ATPasa Intercambiadora de Sodio-Potasio/metabolismoRESUMEN
Maximal steady state (MSS) speed can be determined from blood lactate concentration (HLa); however, this method is not optimal. The purpose of this study was to determine whether near-infrared spectroscopy (NIRS) technology could be used to detect a breakpoint in percent oxygen saturation (StO2) of the muscle and whether the determined breakpoint exercise intensity could be used to determine MSS exercise intensity. Sixteen distance runners and triathletes (men = 9, VO2max = 64.9 +/- 4.9 ml x kg(-1) x min(-1), women = 7, VO2max = 50.8 +/- 7.0 ml x kg(-1) x min(-1)) completed an incremental exercise test. A change from linearity when plotting StO2 or HLa vs. running speed was defined as the breakpoint. The subjects then completed constant speed runs to determine maximal lactate steady state (MLSS). In 12 subjects, breakpoints were identified for both HLa and StO2 values. Predicted MLSS velocities from HLa breakpoint (12.76 +/- 1.63 km x h(-1)), StO2 breakpoint (12.84 +/- 1.58 km x h(-1)), and 4 mM HLa (13.49 +/- 1.71 km x h(-1)) methods from the incremental test did not differ from MLSS speeds (13.04 +/- 2.03 km x h(-1)). A Bland and Altman analysis of agreement between the MLSS and the StO2 breakpoint speeds resulted in a mean difference of 0.14 +/- 0.36, whereas the mean difference between MLSS and HLa breakpoint speeds was 0.19 +/- 0.43. During the incremental test, no StO2 breakpoint was determined in 2 subjects, whereas 2 subjects had no HLa breakpoint. The results of this study lead us to conclude that the NIRS determination of StO2 is a noninvasive technique that is comparable with HLa in determining MSS intensity and therefore appropriate for use in determining exercise training intensity.
Asunto(s)
Músculo Esquelético/fisiología , Resistencia Física/fisiología , Espectroscopía Infrarroja Corta , Adulto , Prueba de Esfuerzo , Femenino , Humanos , Lactatos/sangre , Masculino , Consumo de Oxígeno/fisiología , Carrera/fisiologíaRESUMEN
Observations of athletes in seated and standing cycling positions in laboratory and field settings have led to the perception that they produce different outputs. The purpose of this study was to determine whether there are differences in power output and physiological responses between seated and standing positions of athletes during 3 consecutive Wingate tests. Seven (n = 7) elite-level speedskaters completed 3 x 30-second Wingate tests (resistance = 7.5% body weight) with 3.5 minutes of recovery between each test in both seated and standing positions. During the recovery period, athletes pedaled against no resistance in the seated position. Testing was randomized and separated by at least 48 hours. Power output, heart rate, blood lactate, and muscle oxygenation data were collected. Statistical analysis of comparable tests (i.e., seated Wingate test 1 [WinD1] compared with standing Wingate test 1 [WinU1]; WinD2:WinU2; WinD3:WinU3) revealed no significant differences between the seated and standing variables. Position during a short-duration maximal-effort exercise test on a stationary bike did not produce statistically different results in power, maximal heart rate, blood lactate, or muscle oxygenation. As no differences were detected between positions, practitioners can allow subjects to choose their position. Also, if a subject rises out of the seat during a "seated" test, this change may not affect the subject's physiological variables. However, transitioning from one position to the other during the test is not advised due to the possible chance of injury. It should be acknowledged that there may be reasons for stipulating one position over another (e.g., injuries, leg length).
Asunto(s)
Ciclismo/fisiología , Prueba de Esfuerzo/métodos , Postura/fisiología , Patinación/fisiología , Adolescente , Adulto , Femenino , Frecuencia Cardíaca/fisiología , Humanos , Lactatos/sangre , Masculino , Consumo de Oxígeno/fisiologíaRESUMEN
Diabetes causes oxidative stress in the liver and other tissues prone to complications. Photobiomodulation by near infrared light (670 nm) has been shown to accelerate diabetic wound healing, improve recovery from oxidative injury in the kidney, and attenuate degeneration in retina and optic nerve. The present study tested the hypothesis that 670 nm photobiomodulation, a low-level light therapy, would attenuate oxidative stress and enhance the antioxidant protection system in the liver of a model of type I diabetes. Male Wistar rats were made diabetic with streptozotocin (50 mg/kg, ip) then exposed to 670 nm light (9 J/cm(2)) once per day for 18 days (acute) or 14 weeks (chronic). Livers were harvested, flash frozen, and then assayed for markers of oxidative stress. Light treatment was ineffective as an antioxidant therapy in chronic diabetes, but light treatment for 18 days in acutely diabetic rats resulted in the normalization of hepatic glutathione reductase and superoxide dismutase activities and a significant increase in glutathione peroxidase and glutathione-S transferase activities. The results of this study suggest that 670 nm photobiomodulation may reduce, at least in part, acute hepatic oxidative stress by enhancing the antioxidant defense system in the diabetic rat model.
Asunto(s)
Antioxidantes/metabolismo , Diabetes Mellitus Experimental/terapia , Hígado/metabolismo , Fototerapia , Enfermedad Aguda , Animales , Glucemia/metabolismo , Peso Corporal/efectos de la radiación , Enfermedad Crónica , Diabetes Mellitus Experimental/enzimología , Glutatión/metabolismo , Glutatión Peroxidasa/metabolismo , Glutatión Reductasa/metabolismo , Glutatión Transferasa/metabolismo , Peroxidación de Lípido/efectos de la radiación , Hígado/enzimología , Hígado/efectos de la radiación , Masculino , Malondialdehído/metabolismo , Ratas , Ratas Wistar , Superóxido Dismutasa/metabolismoRESUMEN
Since interest in science classes has declined recently and obesity, especially in youth, continues to increase, an exercise physiology-based course was taught in public parks to promote active-learning science and healthy living. The course emphasized and integrated exercise, nutrition, and health during a 3-h session. Following an introduction, five hands-on laboratory-based student modules were performed. Students performed respiratory, cardiovascular, temperature regulation, energy expenditure, oxygen uptake, and exercise modules. During most modules, the students made measurements at rest and during the performance of exercise at different intensities. The students were very involved and engaged in problem solving throughout the session. The program was given for 10 days to more than 500 students representing 18 classes from 10 different schools. Evaluations indicated that the program was a real-life science experience that gave the students a new understanding of how their bodies worked and the purpose of exercise. The students and teachers also experienced "school learning" put into action as the program fit well with their science curriculum.