The effects of regular aerobic exercise on renal functions in streptozotocin induced diabetic rats

Diabetic nephropathy is a feared complication of diabetes since it can lead to end-stage renal failure and also it is a risk factor of cardiovascular disease. The important clinical problems caused by diabetic nephropathy are proteinuria and decreased renal function. Exercise is a cornerstone of diabetes management, along with diet and medication. Since acute exercise causes proteinuria and decreases glomerular filtration rate, the effect of exercise on diabetic nephropathy is controversial. The aim of this study was to investigate the effect of regular aerobic exercise on microalbuminuria and glomerular filtration rate in diabetic rats. Moderate diabetes was induced by streptozotocin (45 mg/kg IV) in rats and an aerobic exercise-training program on a treadmill was carried out for 8 weeks. Four groups of rats; control sedentary (CS), control exercise (CE), diabetic sedentary (DS) and diabetic exercise (DE) were included in the study. Blood glucose levels were determined from the plasma samples taken at the end of 4 weeks of stabilization period and 8 weeks of training program. Creatinine clearance (CCr) and microalbuminuria (MA) levels were determined to evaluate renal functions. The analyzed data revealed that regular aerobic exercise: 1) significantly decreased the plasma glucose level of the DE group compared to the DS group (p < 0.05), 2) significantly decreased the microalbuminuria level of the DE group compared to those of DS group (p < 0.01), 3) significantly decreased the creatinine clearance levels of the DE and CE groups compared to those of CS group (p < 0.05). The results of this study suggest that despite of decreasing creatinine clearance, regular submaximal aerobic exercise has a preventive effect on development of microalbuminuria and thus may retard nephropathy in diabetic rats. © Journal of Sports Science and Medicine

Determination of an optimal threshold value for muscle activity detection in EMG analysis

It is commonly agreed that one needs to use a threshold value in the detection of muscle activity timing in electromyographic (EMG) signal analysis. However, the algorithm for threshold determination lacks an agreement between the investigators. In this study we aimed to determine a proper threshold value in an incremental cycling exercise for accurate EMG signal analysis. Nine healthy recreationally active male subjects cycled until exhaustion. EMG recordings were performed on four low extremity muscle groups; gastrocnemius lateralis (GL), gastrocnemius medialis (GM), soleus (SOL) and vastus medialis (VM). We have analyzed our data using three different threshold levels: 25%, 35% and 45% of the mean RMS EMG value. We compared the appropriateness of these threshold values using two criteria: (1) significant correlation between the actual and estimated number of bursts and (2) proximity of the regression line of the actual and estimated number of bursts to the line of identity. It had been possible to find a significant correlation between the actual and estimated number of bursts with the 25, 35 and 45% threshold values for the GL muscle. Correlation analyses for the VM muscle had shown that the number of bursts estimated with the 35% threshold value was found to be significantly correlated with the actual number of bursts. For the GM muscle, it had been possible to predict the burst number by using either the 35% or 45% threshold value and for the SOL muscle the 25% threshold value was found as the best predictor for actual number of burst estimation. Detailed analyses of the actual and estimated number of bursts had shown that success of threshold estimation may differ among muscle groups. Evaluation of our data had clearly shown that it is important to select proper threshold values for correct EMG signal analyses. Using a single threshold value for different exercise intensities and different muscle groups may cause misleading results. © Journal of Sports Science and Medicine

The effect of L-(+)-lactate on tension development and excitability in in vitro rat diaphragm muscle

PubMedID: 12391435Background. The aim of this study was to determine the effect of lactate anion, independent of H+, on in vitro rat diaphragm muscle tension development, and to evaluate the changes in excitability by measuring resting membrane potential (RMP) and the amplitude of the sarcolemma action potential (AP). Methods. Diaphragm muscle strips taken from 5 Wistar strain albino rats were placed in a tissue bath aerated with 95% O2 and 5% CO2 continuously at 30°C. The muscle was attached to an isometric force transducer and stimulated indirectly by the phrenic nerve (0.2 msec, 0.5 Hz, and supra-maximally). Two groups were studied, each subjected to a different sequence of 20 min exposures to a high level of lactate (high [La]), (20 mM) or control periods (C) without lactate. The first group was subjected to (C, high [La], C), and the second was subjected to (high [La], C, high [La]). Following the preparation of high [La] solution, pH was adjusted by adding saturated NaOH. In the second part of this experiment conventional microelectrode technique was used to determine the RMP and amplitude of sarcolemma AP of the rat diaphragm muscle. Thirteen muscles were used and 20-30 measurements were performed in both C and high [La] groups. Results. Addition of lactate reduced the mean tension development significantly (p&lt;0.05) at isopH (pH was 7.34±0.001 for C vs 7.33±0.001 for high [La]). Mean values of RMP (84.29±0.29 mV for C, -84.82±0.28 mV for high[La]) and amplitude of sarcolemma AP (118.86±0.72 mV for C, 119.19±0.71 mV for high[La]) did not differ significantly. Conclusions. We conclude that lactate reduces tension development at iso-pH without altering the amplitude of sarcolemma AP and RMP

Support vector machines for aerobic fitness prediction of athletes

Support vector machine is a statistical learning classifier, based on the principle of structural risk minimization, which performs well when applied to data outside the training set. This paper presents a new approach based on support vector machines to predict whether an athlete is aerobically fit or not. The input data set contains physical properties of athletes as well as their cardiopulmonary exercise testing results which were obtained at Cukurova University Sports Physiology Laboratory. According to the exercise test protocol, speed and grade of the treadmill were increased at certain times and the input variables of time, speed and grade of the treadmill, and oxygen uptake, carbon dioxide output, minute ventilation and heart rate of athletes were recorded. The average of the exercise test data was taken over certain time intervals and a curve fitting algorithm was applied to remove the spikes in the data and make it more suitable to use with support vector machines. Experiments with several different training and test data show that curve-fitted data has better performance measures, such as higher prediction rate, sensitivity, specificity, and shorter training time. © 2008 Elsevier Ltd. All rights reserved

Changes in substrate utilization rates during 40 min of walking within the Fatmax range

PubMedID: 31560234BACKGROUND AND AIMS: The aim of this study was to evaluate changes in fat oxidation rate during 40 min of continuous exercise and identify the intensity at the highest fat oxidation rate (Fatmax). METHODS: A total of 14 sedentary males with age, body height, weight, and BMI averages of 29.3?±?0.7 years, 178.3?±?1.7 cm, 81.1?±?3.9 kg, and 25.4?±?0.9 kg/m2, respectively, were included in the study. Fatmax was determined using an indirect calorimeter with an incremental treadmill walking test at least after 12 h of fasting. On a separate day, at least after 12 h of fasting, the participants walked for 40 min within their predetermined individual Fatmax heart rate and speed ranges. RESULTS: The initial fat oxidation rate was not sustained within the first 16 min of exercise and was reduced; however, carbohydrate oxidation reached a stable level after nearly 10 min. CONCLUSIONS: In sedentary individuals, during low-intensity physical activity, fat oxidation rates may not be sustainable as expected from Fatmax testing. Therefore, when exercise is prescribed, one should consider that the fat oxidation rate might decrease in sedentary overweight individuals

A comparison of the maximal fat oxidation rates of three different time periods in the Fatmax stage

PubMedID: 30787650This study aimed to compare the maximal fat oxidation (MFO) rates obtained from the stage average, last 2 min average, and highest value in the Fatmax stage determined with a 6 min step protocol. A total of 35 overweight, sedentary healthy men (age: 25.4 ± 0.7 years, body mass index: 26.0 ± 0.6 kg/m 2 ) participated in the study. Substrate oxidation was calculated using breath-bybreath gas exchange data for each stage. When the change in the fat oxidation rate for every min throughout the Fatmax stage was evaluated, the average value of the 4th min was significantly lower than that of the 2 nd and 3 rd min (p &lt; 0.01). In addition, the 5th and 6th min fat oxidation rates were significantly lower than the rates of the 1 st , 2 nd , 3 rd , and 4th min (0.30 ± 0.01 and 0.29 ± 0.01 g/min for the 5 th and 6 th min, respectively, vs. 0.35 ± 0.02, 0.34 ± 0.02, 0.33 ± 0.02, and 0.31 ± 0.01 g/min for the 1 st , 2 nd , 3 rd , and 4 th min, respectively; p &lt; 0.01). Most of the participants had MFO rates in the 1 st min of the stage (16/35 participants), and the MFO rates of the remaining participants were observed in the 2 nd , 3 rd , and 4 th min (7/35, 4/35, and 8/35 participants, respectively). None of the participants had MFO rates in the 5 th or 6 th min. The individual MFO rate (highest fat oxidation rate during Fatmax) was significantly higher than the fat oxidation rate calculated with the last 2 min average values (0.36 ± 0.02 and 0.30 ± 0.01 g/min, respectively; p &lt; 0.05). In conclusion, the calculation of the fat oxidation rate by averaging the last portion of the Fatmax stage data may cause the underestimation of the MFO rate, which probably occurs earlier in the Fatmax stage. © Journal of Sports Science and Medicine

Living, training and playing in the heat: Challenges to the football player and strategies for coping with environmental extremes

PubMedID: 21029198Dehydration and hyperthermia both, if sufficiently severe, will impair exercise performance. Dehydration can also impair performance of tasks requiring cognition and skill. Body temperature may exceed 40 °C in competitive games played in hot weather, but limited data are available. Football played in the heat, therefore, poses a challenge, and effects on some aspects of performance become apparent as environmental temperature increases above about 12-15 °C. Prior acclimatization will reduce the impact of high environmental temperatures but provides limited protection when humidity is also high. Ingestion of fluids is effective in limiting the detrimental effects on performance: drinks with added carbohydrate and electrolytes are generally more effective than plain water and drinks may be more effective if taken cold than if taken at ambient temperature. Pre-exercise lowering of body temperature may aid some aspects of performance, but the efficacy has not been demonstrated in football. © 2010 John Wiley & Sons A/S

Analysis of isokinetic knee extension/flexion in male elite adolescent wrestlers

Wrestling requires strength of the upper and lower body musculature which is critical for the athletic performance. Evaluation of the adolescent's skeletal muscle is important to understand body movement, especially including those involved in sports. Strength, power and endurance capacity are defined as parameters of skeletal muscle biomechanical properties. The isokinetic dynamometer is an important toll for making this type of evaluation. However, load range phase of range of motion has to be considered to interpret the data correctly. With this in mind we aimed to investigate the lover body musculature contractile characteristics of adolescent wrestlers together with detailed analyses of load range phase of motion. Thirteen boys aged 12 - 14 years participated to this study. Concentric load range torque, work and power of knee extension and flexion were measured by a Cybex Norm dynamometer at angular velocities from 450°/sec to 30°/sec with 30°/sec decrements for each set. None of the wrestlers were able to attain load range for angular velocities above 390°/sec and 420°/sec for extension and flexion respectively. Detailed analyses of the load range resulted in statistically significant differences in the normalized load range peak torque for extension at 270°/sec (1.44 ± 0.28 Nm·kg-1 and 1.14 ± 0.28 Nm·kg-1 for total and load range peak torque respectively, p &lt; 0.05), and for flexion at 300°/sec (1.26 ± 0.28 Nm·kg-1 and 1.03 ± 0.23 Nm·kg-1 for total and load range peak torque respectively, p &lt; 0.05), compared to total peak torque data. Similarly, the significant difference was found for the work values at 90°/sec (1.91 ± 0.23 Nm·kg-1 and 1.59 ± 0.24 Nm·kg-1 for total and load range work respectively for extension and 1.73 ± 0.21 Nm·kg-1 and 1.49 ± 0.19 Nm·kg-1 for total and load range work respectively for flexion, p &lt; 0.05), and was evident at higher angular velocities (p &lt; 0.001) for both extension and flexion. At extension, load range power values were significantly smaller than total power for all angular velocities except 150°/sec (p &lt; 0.05 for 120 and 180°/sec, p &lt; 0.001 for others). Finally, load range flexion power was found to be higher than total power with statistically significance (p &lt; 0.05 for 60, 120, 150, 180, 210, 270 and 300°/sec, p &lt; 0.001 for 240°/sec). Extra caution is required for correct interpretation of load range data in terms of considering the load range during limb movement. Evaluation of muscle performance of these adolescent wrestlers at regular intervals may give us an opportunity to obtain a healthy maturation profile of these adolescent wrestlers. ©Journal of Sports Science and Medicine (2005)

Effect of hot environmental conditions on physical activity patterns and temperature response of football players

PubMedID: 21029201Heat stress may contribute to decreased match performance when football is played in extreme heat. This study evaluated activity patterns and thermal responses of players during soccer matches played in different environmental conditions. Non-acclimatized soccer players (n=11, 20±2 years) played two matches in conditions of moderate heat (MH) and high heat (HH) index. Core temperature (Tc) and physical performance were measured using a telemetric sensor and a global positioning system, respectively. The average ambient temperature and relative humidity were MH 34±1 °C and 38±2%; HH 36±0 °C and 61±1%. Peak Tc in the MH match was 39.1±0.4 °C and in the HH match it was 39.6±0.3 °C. The total distance covered in the first and second halves was 4386±367 and 4227±292 m for the MH match and 4301±487 and 3761±358 m for the HH match. Players covered more distance (P&lt;0.001) in the first half of the HH match than in the second half. In football matches played at high environmental temperature and humidity, the physical performance of the players may decrease due to high thermal stress. © 2010 John Wiley &amp; Sons A/S