Electrical Stimulation While Resistance Training Leads to Greater Gains in Muscle Mass and Strength

Resistance training (RT) has long been shown to increase muscle strength and muscle mass and is widely recommended for people of all ages and ability levels. Neuromuscular electrical stimulation (NMES) is an involuntary mode of inducing muscle contractions that has been used to prevent muscle immobility, weakness, strength loss, and muscle loss in rehabilitative settings. However, the additive effects of NMES and RT are not well established. PURPOSE:. To determine if superimposing neuromuscular electrical stimulation during a resistance training intervention elicits greater gains in muscle strength and/or muscle mass than resistance training being performed alone. METHODS: An electronic search was performed from EBSCO, GoogleScholar, PubMed, and ResearchGate to identify all original research investigating the effects of superimposed NMES and RT on muscle strength and muscle mass. Studies that met the inclusion criteria for the meta-analyses were included if the study design was a randomized controlled trial with NMES being superimposed during RT and outcome measure included muscle strength and/or muscle mass. Effect sizes were calculated as the standard mean difference (SMD) using a pooled standard deviation (SD) and meta-analyses were computed using random effects models. RESULTS: Sixteen studies met the inclusion criteria for systematic review with 14 of those being included in the meta-analysis (n=8 for strength, n=1 for muscle mass, n=5 reported both). The meta-analyses comprised of 347 subjects demonstrated that superimposing NMES during a RT intervention has a significant additive effect on increase in muscle strength (SMD: 0.21; 95% CI: 0.03 to 0.38; p = 0.02; I² = 73.05%) as well as increase in muscle mass (SMD: 0.26; 95% CI: 0.04 to 0.49; p = 0.02; I² = 21.45%), compared to performing RT alone, in a healthy population. CONCLUSION: Use of NMES during RT results in greater gains in muscle strength and muscle mass when compared to resistance training performed alone. Incorporation of NMES during RT may be a more effective strategy to improve muscle strength and muscle mass. Future studies should determine whether use of NMES concurrently with RT may have additive effects on metabolic and/or cardiovascular health

Improved Glucose Tolerance and Glucose Utilization with Neuromuscular Electrical Stimulation

Sedentariness and increased body fat are the leading risk factors for developing insulin resistance, obesity, and type 2 diabetes. We have shown that muscle contraction induced by electrical pulse stimulation increase GLUT4 content in an in vitro primary cell culture model. Neuromuscular electrical stimulation (NMES) is a novel alternative strategy to induce muscle contraction in humans. Although widely used in rehabilitation settings to prevent muscle atrophy, effectiveness of NMES-induced muscle contractions in improving metabolic health is not clear. PURPOSE: To investigate the effects of four weeks of NMES on glucose tolerance, substrate utilization, and muscle mass in a sedentary overweight/obese population. METHODS: Sedentary overweight/obese participants were randomized into either a control (n=5; age: 42.2 ± 5.0 years; BMI= 32.8 ± 1.5 kg/m2) or NMES (n=5; age: 30.3 ± 4.5 years; BMI= 32.7 ± 2.3 kg/m2) group. All participants received bilateral quadriceps stimulation (12 sessions; 30 minutes/session; 3 times/week) either using low intensity sensory level (control) or at high intensity neuromuscular level (NMES) for four weeks (50Hz; 300ms pulse width). Insulin sensitivity was assessed by three-hour oral glucose tolerance test (OGTT), substrate utilization was assessed by measuring blood lactate (acute effects) and indirect calorimetry (respiratory quotient, RQ) and body composition was measured by dual X-ray absorptiometry. RESULTS: Control and NMES groups had comparable fasting blood glucose (Control 110.2 ± 21.1; NMES 96 ± 3.9 mg/dL; p=0.53), glucose tolerance (Control 430.73 ± 20.23; NMES 455.55 ± 26.07; AU; p=0.49), substrate utilization measured by RQ (Control 0.78 ± 0.02; NMES 0.78 ± 0.02; p=0.99), and muscle mass (Control 48.6 ± 5.5; NMES 47.3 ± 4.3; kg; p=0.86) at baseline. Four weeks of NMES resulted in a significant improvement in blood glucose measured after 2 hours of glucose drink consumption during OGTT (150.90 ± 7.59 to 138.20 ± 7.61 mg/dL, p=0.03) whereas no change was observed in control group (151.75 ± 6.14 to 173.20 ± 34.17 mg/dL, p=0.12). Insulin sensitivity measured by glucose area under the curve (AUC), trended to improve with NMES (455.55 ± 26.07 to 415.36 ± 25.89 AU; p=0.07), whereas no change was observed in control (430.73 ± 20.23 to 494.68 ± 77.21 AU; p=0.32). Lactate accumulation (AUC) assessed during 30 min of NMES was significantly greater compared to that of control group (Control 0.87 ± 0.07; NMES 1.22 ± 0.14 AU; pCONCLUSION:NMES is a novel and effective strategy to improve glucose utilization and insulin sensitivity in an at-risk overweight/obese sedentary population in the absence of substrate utilization and muscle mass improvement. This project was funded by student research development award by Texas chapter of American College of Sports Medicine

The Effects of Two Different Sprint Training Modalities on Sprint Speed, Aerobic Fitness and Body Composition

Previous studies on sprint training have shown subjects to improve not only sprint speed, but also aerobic fitness and body composition. However, it is unclear whether sprint training on the track is more effective in improving these variables compared to training on a high-speed treadmill. The purpose of this study was to examine the effects of a 6-week track (TR) vs. high-speed treadmill (TM) sprint training on maximal aerobic capacity (VO2max), sprint speed and body composition. Twelve subjects were randomly assigned to the TR (n=6; 3 males, 3 females) or TM training group (n=6; 3 males, 3 females). All subjects performed 2 training sessions weekly, performing 4 maximal sprints with 3-4 minutes rest in between attempts. Four cones were placed along the track to simulate progression of speed to replicate treadmill conditions. TR started from an upright jog position and progressively increased speed at each cone (60%, 70%, 80%, and 90%) of maximal speed and 100% maximal speed through the recording zone (5-6 seconds). A treadmill speed test was applied increasing treadmill speed to the subjects’ loss of control, while suspended in a safety harness. VO2max was measured by Parvomedics True Max 2400 metabolic cart and body composition was measured by Dual Energy X-ray absorptiometry (DXA) at baseline and after the 6 weeks of training. Treadmill sprint speed improved significantly in both groups (TR 16.36±0.54 to 17.79±0.52 miles/hr, p=0.0003; TM 17.13±0.84 to 18.63±0.93 miles/hr, p=0.0018). VO2 max was improved in both groups (TR 46.60±2.03 to 49.54±1.71 ml/kg/min, p=0.03; TM 47.59±4.152 to 51.05±4.445 ml/kg/min, p=0.04). There was no significant change in body mass index (TR 24.1±1.0 to 24.0±1.0 kg/m2; p=0.51; TM 24.5±0.7 to 24.1±0.8; p=0.30) or in lean mass (TR 44.08±3.12 to 43.80±2.62 kg; p=0.73; TM 48.41±5.29 to 44.55±7.49 kg; p=0.36) in either group. There was a significant decrease in percent body fat in the TR group (30.36±3.75 to 29.20±3.75%; p=0.01) but not in the TM group (27.83±5.50 to 27.20±5.95%; p=0.38). In summary, both the track and treadmill sprint training modalities appear to be effective to improve sprint speed and aerobic power after only 6 weeks of training. However, only track sprint training appears to be beneficial towards decreasing body fat

Adiposity and High-Density Lipoprotein are Reflective of Blood Pressure among Individuals without Hypertension

Obesity and abnormal lipid profiles have been linked to hypertension and other cardiometabolic risks. Early identification of cardiovascular risks factors in healthy individuals is important for disease prevention and maintaining a high quality of life. PURPOSE: This study sought to determine whether adiposity and lipid profile in a non-hypertensive, otherwise healthy population, is associated with blood pressure, a hallmark of cardiovascular disease risk. METHODS: Seventy-seven individuals (34 males 43 females; age 25.4 ±7.7 years; BMI 27.2 ± 5.2 kg/m2) without hypertension (systolic blood pressure (SBP) 110.3 ± 10.3 mmHg; diastolic blood pressure (DBP) 71.48 ± 7.93 mmHg) from the border region of El Paso participated in this study. Anthropometric measurements were taken. Blood pressure was measured by sphygmomanometer. Adiposity (percent body fat) and abdominal fat distribution (android/gynoid ratio) were measured by dual energy X-ray absorptiometry. Lipid profile (triglycerides (TG), total cholesterol (TC), high-density lipoprotein (HDL) and low-density lipoprotein (LDL)) were measured by automated serum chemistry analyzer. The relationship between various body composition indices, lipid profile and blood pressure were determined by Pearson correlation at an alpha level of 0.05. RESULTS: Body mass index positively correlated with SBP (r=0.30, p0.05). TG, TC and LDL did not correlate with SBP nor DBP. CONCLUSION: Higher body fat and android/gynoid ratio, and lower HDL corresponds to higher blood pressure among individuals without hypertension. Early measures to control adiposity and maintenance of a healthy lipid profile may help maintain healthy blood pressure and ultimately, the prevention of cardiovascular diseases in a healthy, non-hypertensive population

Exercise Mediated Improvements in Insulin Sensitivity and Metabolic Flexibility Are Not Inhibited by a Family History of Type 2 Diabetes

ABSTRACT A family history of diabetes (FH+) is considered a risk factor for the development of insulin resistance and type 2 diabetes. However, it is not known whether exercise induced improvement in insulin sensitivity (IS) and metabolic flexibility (MF) are impacted by a FH+, compared to those without (FH-). PURPOSE: To determine if a FH+ limits exercise induced improvements in IS, MF, body composition, and strength following an 8-week combined aerobic and resistance training intervention. METHODS: 20 sedentary, normoglycemic, Mexican-American males underwent 8-weeks of combined exercise training 3 times/week (35-min aerobic & 45-min resistance training/session). A controlled diet was provided 5 days before pre/post intervention tests. IS was assessed by hyperinsulinemic euglycemic clamp. MF was assessed by change in respiratory quotient (ΔRQ) at the insulin stimulated state of the clamp compared to the fasted state. Body composition was measured using DXA. Upper/lower body strength were measured by 1 repetition maximum bench press and leg strength dynamometer. RESULTS: IS significantly improved in both groups (FH- 3.05±0.25 to 3.74±0.29ml/kg estimated metabolic body size (EMBS), p=0.05; FH+ 3.53±0.46 to 4.83±0.51ml/kg EMBS; p=0.006). MF significantly improved in both groups (FH- 0.72±0.009 to 0.78±0.008, p=0.0006; FH+ 0.71±0.01 to 0.81±0.02, p=0.0001). Fat free mass significantly improved in both groups (FH- 55.62±2.19 to 57.71±2.06kg, p=0.02; FH+ 51.77±1.95 to 53.45±1.79kg, p=0.0002) Upper body strength (FH- 164.78±20.69 to 190.50±21.10lb, p=0.00001; FH+ 145.45±15.55 to 178.00±16.75lb, p=0.00001) and lower body strength (FH- 360.00±29.13 to 417.00±24.64lb, p=0.007; FH+ 346.36±20.63 to 419.50±15.99lb, p=0.00003) significantly increased in both groups. Degrees of improvement in IS was not different between groups (FH- 28.2±12.13% vs. FH+ 41.66±11.87%; p\u3e0.05). CONCLUSION: FH+ is not a limiting factor for exercise induced improvements in IS, MF, body composition, and strength in normoglycemic Mexican Americans

Does Having a Glucose Peak Time within 30 Minutes of Glucose Ingestion Indicate Better Metabolic Flexibility?

Metabolic flexibility is the ability of the body to physiologically adapt to fuel oxidation in response to fuel availability assessed by change in respiratory quotient (DRQ) from fasted to glucose/insulin-stimulated states. Glucose peak time describes the time of the highest plasma glucose concentration during an oral glucose tolerance test (OGTT). Peak time \u3e30 minutes has been associated with increased odds of prediabetes compared to peak times ≤30 minutes. PURPOSE: The purpose of the study was to determine if glucose peak time withing 30 minutes of glucose ingestion during an OGTT is indicative of better substrate utilization. METHODS: Sixty-two healthy participants without diabetes (34 males, 28 females) participated in this study (Age 26.02 ± 8.25 years; BMI 28.91 ± 4.71 kg/m2). Blood glucose levels were measured during an OGTT at 0, 30, 60, 90, 120, 150, and 180 minutes. Participants were classified in two groups based on whether glucose level reached its peak at 30 min (≤30) or after 30 min (\u3e30) during the OGTT. Substrate utilization was assessed by measuring respiratory quotient (RQ) using indirect calorimetry. Metabolic flexibility was calculated from the change in RQ (DRQ) from fasted to postprandial condition. Groups were compared using unpaired t-test. RESULTS: Fasting blood glucose was not significantly different between participants with peak time ≤30 minutes and peak time \u3e30 (96.15 ± 11.50 vs. 98.20 ± 11.14 mg/dL; p=0.49). Fasting RQ was also not significantly different between two groups (0.78 ± 0.07 vs. 0.77 ± 0.08; p=0.84). However, post-prandial RQ for participants with glucose peak time ≤30 minutes was significantly higher compared with those with peak time \u3e30 minutes (0.83 ± 0.07 vs. 0.77 ± 0.04; p=0.002 respectively). The change in RQ (DRQ) tended to be higher for participants with peak time ≤30 minutes compared with those with peak time \u3e30 minutes (0.06 ± 0.05 vs. 0.03 ± 0.05; p=0.06 respectively). CONCLUSION: Glucose peak time of ≤30 minutes does indicate greater glucose utilization compared with peak time \u3e30 minutes evident by post-prandial RQ, however since DRQ was not statistically different, based on our data we are unable to conclude that peak time ≤30 minutes is indicative of better metabolic flexibility compared with \u3e30 minutes. Further research in this area is needed

Gender Difference in the Relationship of Fatigue Index, Anaerobic Power and Capacity to Body Composition and Bone Mineral Status in Non-Athletes

The fatigue index is considered an important indicator of anaerobic fitness. The lower the fatigue index, the greater the ability of the body to maintain its power output through an anaerobic performance. The Wingate test is widely used by coaches, athletes, and researchers to measure lower body power, anaerobic capacity, and fatigue index. Body composition is considered an important component of anaerobic fitness, it is not clear how gender may influence the relationship between body composition and anaerobic fitness. PURPOSE: The purpose of this study was to understand how gender may impact the relationship between body composition and anaerobic fitness in a non-athlete population. METHODS: Fourteen non-athletes (M=7/F=7, age 27.31 ± 6.8 years; BMI 25.5 ± 5.4 kg/m²) volunteered to participate in this study. Peak power, anaerobic capacity, and fatigue index were assessed by the Wingate test. Following a three-minute warm-up, the participant began to pedal as fast as possible for fifteen seconds without any resistance, then a calculated resistance of 0.092 kg x.kg-1 body mass for males and 0.075 kg x.kg-1 body mass for females were applied to the flywheel and the participant continued to pedal for the duration of the test (30s). Body composition including bone mineral density (BMD) and bone mineral content (BMC) was assessed by dual-energy x-ray absorptiometry (DXA). General characteristics of the participants were presented as means and standard deviation (SD). Unpaired t-test was used for statistical comparison between the female and male groups. Pearson correlation coefficients were used to express the relationships between anaerobic test parameters and body composition parameters. RESULTS: Body weight and body mass index (BMI) were not significantly different between females and males (p=0.73 and p= 0.94 respectively). Fatigue index positively correlated with BMI (r= 0.89, p=0.02) and negatively correlated with percent lean mass (r = -0.86, p= 0.03) and bone mineral content (BMC, %) (r= -0.84, p= 0.04) in females whereas no correlation between fatigue index and body composition parameters was found in males. Peak power was significantly correlated with BMI (r=0.83, p=0.04) and BMD (r=0.93, p=0.01) in females but not in males. Likewise, Anaerobic capacity was also significantly correlated to BMI (r=0.94, p=0.01) and BMD (r=0.86, p=0.03) in females. But not in males. CONCLUSION: Anaerobic fitness parameters are associated with BMI and BMC in females but not in males. Our study suggested body composition components could be a reliable predictor of the ability to maintain anaerobic power in females and it could be an indicator of anaerobic performance in this population

Biphasic Glucose Curve Morphology Reflects Better Glucose Tolerance and Substrate Utilization

The shape of glucose curve during an oral glucose tolerance test is a plausible risk factor for insulin resistance and other metabolic disorders and could be a potential biomarker for predicting risk for developing diabetes. PURPOSE: This study aimed to compare the glucose tolerance and substrate utilization between monophasic and biphasic glucose curve morphologies. METHODS: A total of 50 subjects (33/17 male/female; Age: 27 ± 7.74 years; BMI: 27.7 ± 4.97 kg/m2) without diabetes were tested for a two-hour oral glucose tolerance after ingesting 75g of glucose drink. Blood glucose levels were measured at time points 0, 15, 30, 60, 90, and 120 min. Based on the shape of glucose response curve, subjects were classified as either monophasic (when blood glucose level peaks and is followed by a decline in blood glucose level ≥4.5 mg/dL within the 120min test) or biphasic (when blood glucose level rises a second time within the 120min test, with both the initial decline and second rise in glucose levels being ≥4.5 mg/dL). Substrate utilization, body composition, and physical activity level were assessed using a metabolic cart, dual x-ray absorptiometry, and an activity monitor respectively. RESULTS: There were no significant differences in age, BMI, fasting blood glucose, fasting respiratory quotient, and body fat percentage between monophasic and biphasic glucose groups (p \u3e 0.05). The biphasic group was more glucose tolerant compared to the monophasic group as indicated by a lower glucose level at 60min post glucose ingestion (141.02 ± 25.90 vs 173.04 ± 37.64 mg/dL; p= 0.001), and glucose area under the curve after 120min (272.09 ± 39.61 vs 304.80 ± 49.32 AU; p=0.014). There was no significant difference in metabolic flexibility between groups (p\u3e0.05); however, glucose/insulin stimulated respiratory quotient was comparatively higher among the biphasic group (0.82 ± 0.07 vs 0.78 ± 0.05; p= 0.027). Additionally, the biphasic group was more physically active than the monophasic group (1.28 ± 0.03 vs 1.25 ± 0.02; p= 0.012). CONCLUSION: Monophasic glucose curve morphology is an indicative biomarker of lesser carbohydrate metabolism and glucose intolerance; hence, glucose curve morphology should be considered as an important feature of the conventional oral glucose tolerance test for medical screening

Effects of Neuromuscular Electrical Stimulation on Energy Expenditure and Oxygen Consumption

Exercise is beneficial to improve metabolic diseases such as obesity and type 2 diabetes. Physical activity results in an increase in energy expenditure (EE) and oxygen consumption due to increased energy demand. Neuromuscular electrical stimulation (NMES) is an alternative strategy to induce muscle contraction. Our previous work have shown that NMES induced muscle contraction can improve metabolic health in an overweight and obese population. However, it is not known whether NMES induced muscle contraction leads to greater energy expenditure. PUPROSE: To determine the effect of NMES induced muscle contraction on energy expenditure and oxygen consumption. METHODS: Eighteen sedentary overweight/obese men (n=6) and women (n=9) participated in this study (Age: 35.0 ± 13.3 years; BMI: 32.3 ± 8.4 Kg/m2). All participants received 30 minutes of stimulation up to maximum tolerable intensity to induce visible muscle contraction (pulse duration 300 ms; frequency 50 Hz). Whole body energy expenditure and oxygen consumption were measured continuously for 50 minutes using indirect calorimetry. After 20 minutes of resting measurement, NMES was performed for following 30 minutes. Energy expenditure and oxygen consumption data was sampled every 5 minutes during NMES and an average value for 30 minutes of NMES was calculated. Results were analyzed using Graph Pad Prism software (version 9.2). Paired t-test was used to compare baseline vs. mean energy expenditure and oxygen consumption. One-way ANOVA was also used to determine the significant changes in energy expenditure and oxygen consumption at different time points during stimulation. RESULTS: Average energy expenditure (18.6 ± 0.8 Kcal/Kg to 18.8 ± 1.0 Kcal/Kg, pCONCLUSION:Neuromuscular electrical stimulation results in significant increase in energy expenditure and oxygen consumption. NMES could be used a viable alternative to increasing daily energy expenditure in a sedentary overweight and obese population and for people who are incapable of performing exercise

A Family History of Type 2 Diabetes does Not Impact Maximal Aerobic Capacity in Normoglycemic, Hispanic Males

A family history of type 2 diabetes (FH+) is considered a risk factor for insulin resistance and poor cardiorespiratory fitness. However, it is not known if a FH+ impedes exercise-induced improvements in maximal aerobic capacity (VO2max). Purpose: The purpose of this study was to determine if normoglycemic, sedentary, Hispanic men with FH+ have a lower VO2max compared to those without a family history of type 2 diabetes (FH-) and if the improvement in VO2max after 8-weeks of combined exercise training is comparable between FH- and FH+. Methods: 20 participants underwent 8 weeks of combined exercise training (35 min aerobic at 60-75% VO₂max followed by 6 full-body resistance exercises) 3x/week. VO₂max was measured using ParvoMedics 2400 metabolic measurement system during a standardized graded exercise test performed on a treadmill. Body composition was assessed by dual-energy x-ray absorptiometry. Results: There was no difference in VO2max at baseline regardless of family history (3.57 ± 1.7 vs. 3.91 ± 0.21 L/min; p=0.22). Eight weeks of combined exercise training significantly improved VO₂max (3.57 ± 0.17 to 3.82 ± 0.16 L/min; p=0.002) in FH+, and tended to increase VO2max in FH- (3.91 ± 0.21 to 4.06 ± 0.21 L/min; p=0.09). There was no difference in VO2max between groups after 8 weeks of exercise training (p=0.67). Lean body mass significantly improved in both groups (FH+ 50.7 ± 1.7 to 53.5 ± 1.79 kg; pConclusions: A family history of diabetes shows no effect on cardiorespiratory fitness in a normoglycemic, sedentary, Mexican American population