The accuracy of ten common resting metabolic rate prediction equations in men and women collegiate athletes

Predictive resting metabolic rate (RMR) equations are widely used to determine total daily energy expenditure (TDEE). However, it remains unclear whether these predictive RMR equations accurately predict TDEE in the athletic populations. The purpose of this study was to examine the accuracy of 10 commonly used RMR prediction equations (Cunningham, De Lorenzo, Freire, Harris-Benedict, Mifflin St. Jeor, Nelson, Owen, Tinsley, Watson, Schofield) in collegiate men and women athletes. One-hundred eighty-seven National Collegiate Athletic Association Division III men (n = 97) and women (n = 90) athletes were recruited to participate in one day of metabolic testing. RMR was measured using indirect calorimetry and body composition was analyzed using air displacement plethysmography. A repeated measures ANOVA with Bonferroni post hoc analyses was selected to determine mean differences between measured and predicted RMR. Linear regression analysis was used to assess the accuracy of each RMR prediction method (p<0.05). All prediction equations significantly underestimated RMR (p<0.001), although there was no difference between the De Lorenzo and Watson equations and measured RMR (p = 1.00) for women, only. In men, the Tinsley and Freire equations were the most agreeable formulas with the lowest root-mean-square prediction error value of 404 and 412 kcals, respectively. In women, the De Lorenzo and Watson equations were the most agreeable equations with the lowest root-mean-squared error value of 171 and 211 kcals, respectively. The results demonstrate that such RMR equations may underestimate actual energy requirements of athletes and thus, practitioners should interpret such values with caution.Highlights All prediction equations significantly underestimated RMR in men athletes.All prediction equations, except for the De Lorenzo and Watson equations, significantly underestimated RMR in women athletes.Although a significant underestimation of RMR in men athletes, the Freire and Tinsley equations were the most agreeable prediction equations.In women athletes, the De Lorenzo and Watson equations were the most agreeable prediction equations.

The Effects of Acute Caffeine Supplementation on Repeated-Sprint Ability in Healthy Young Non-Athletes

The ergogenic effects of caffeine supplementation on repeated-sprint ability (RSA) have produced equivocal results. This study aimed to examine the effects of 200 mg of caffeine during repeated-sprint running on heart rate (HR), rating of perceived exertion (RPE), blood lactate (BLa) concentration, and sprint time (ST). Thirty-two individuals (males: n = 17, females: n = 15; age: 22 ± 1 years) participated in the study. The study followed a double-blind, randomized, placebo-controlled, crossover design, in which each participant ingested 200 mg of caffeine or placebo on separate visits 60 minutes prior to repeated-sprinting exercise. The repeated-sprint protocol consisted of three sets of six maximal-effort 30-meter sprints with 20 seconds and 5 minutes of active recovery in between sprints and sets, respectively. During each set, HR, RPE, BLa, and ST were recorded. Caffeine supplementation did not significantly (set 1: p = 0.535; set 2: p = 0.602; set 3: p = 0.189) impact HR during exercise. Similarly, RPE was not statistically (p = 0.052) altered between conditions during any of the sprint sets. The caffeine trials elicited greater BLa values after all three sets compared to the placebo trials (p < 0.001). Moreover, the caffeine trials demonstrated significantly reduced total STs during all sets compared to the placebo trials (p < 0.001). Thus, our findings suggested that 200 mg of caffeine supplementation elicited an increase in RSA in young, healthy non-athletes. These findings are accompanied by a blunted perceived exertion relative to an increase in exercise intensity during repeated-sprint exercise.

Relationship between training load and recovery in collegiate American football players during pre-season training

Background: The purpose of this study was to examine the relationship between training load and next-day recovery in collegiate American football (AF) players during pre-season.Methods: Seventeen athletes (Linemen, n = 6; Non-linemen, n = 11) participated in the 14-day study wearing monitoring (accelerometer + heart rate) sensors during on-field practice sessions throughout pre-season to assess the physiological (PL), mechanical load (ML) and recording of session RPE (sRPE load) immediately post-practice. Prior to practice, participants completed a drop-jump reactive strength index (RSI) test and reported perceived recovery status (PRS). Loaded counter movement vertical jump was assessed before and after pre-season.Results: For every one unit increase in sRPE load, RSI declined by 0.03. Non-linemen had a lower RSI value of 73.1 units compared to linemen. For every one unit increase in ML, the PRS decreased by 0.01. Non-linemen recorded higher average ML during week 2 (ES = 1.17) compared to linemen. Non-linemen recorded higher RSI values in weeks 1 (ES = -1.41) and 2 (ES = -1.72) compared to linemen. All training load and recovery parameters were lower week 2 compared to week 1 (p < 0.05) for all players.Conclusions: Next-day RSI values were influenced by sRPE load while next-day PRS appears to be more influenced by ML. No difference in PL or sRPE load was observed been groups despite non-linemen completing a higher ML throughout the preseason. A combination of training load and recovery metrics may be needed to monitor the fatigue and state of readiness of each player.

Prevalence and Amounts of Common Ingredients Found in Energy Drinks and Shots

BACKGROUND

Energy drinks are one of the most popular packaged beverage products consumed within the United States (US). Energy drinks are considered a functional beverage, a category that also includes sports drinks and nutraceutical beverages.

PURPOSE

The focus of the current study was to examine the nutrition fact panels of the top selling commercially available energy drink and energy shot products within the US to characterize common ingredient profiles to help establish a standard definition and ingredient profile of energy drinks and energy shots for consumers, health care practitioners, and researchers.

METHODS

The top 75 commercially available energy drinks and shots were identified and compiled from multiple commercial retail websites as of September 2021. For the purpose of this study, an energy drink must have met the following criteria: (A) marketed as an energy drink; (B) purported to improve energy, focus, or alertness; (C) not sold as a dietary supplement (no supplement fact panels); (D) manufactured as a pre-packaged and ready-to-drink beverage; and (E) contains at least three of (1) caffeine, (2) B-vitamins, (3) sugar, (4) taurine, (5) creatine, (6) quercetin, (7) guarana, (8) ginseng, (9) coenzyme Q10, or (10) branched chain amino acids. Energy shots must have met similar criteria to be included: (A) marketed as an energy shot; (B) purported to improve energy, focus, or alertness; (C) sold as a dietary supplement; (D) manufactured as a pre-packaged beverage with a small volume (<3.5 mL); and (E) contains at least three of the ingredients stated above.

RESULTS

Twenty energy shots and fifty-five energy drinks were included in this analysis. The number of ingredients per product (mean ± SD) was 18.2 ± 5.7, with 15 products containing proprietary blends with undisclosed ingredient amounts. The relative prevalence and average amounts of the top ingredients were as follows: caffeine (100%; 174.4 ± 81.1 mg), vitamin B6 (72%; 366.9 ± 648.1 percent daily value (%DV)), vitamin B3 (67%; 121.44 ± 69.9% DV), vitamin B12 (67%; 5244.5 ± 10,474.6% DV), vitamin B5 (37.3%; 113.6 ± 76.6% DV), and taurine (37.3%; amounts undisclosed).

CONCLUSIONS

Our findings suggest a high prevalence of caffeine and B-vitamins in these energy products, with many of the formulations containing well above the recommended daily value of B-vitamins.

Higher Body Mass Index Values Do Not Impact Physical Function and Lower-Extremity Muscle Strength Performance in Active Older Individuals

This study examined the potential impact of BMI on physical function and lower-extremity muscle strength (leg extension and flexion peak torque) performance in active/trained older individuals. Sixty-four active/trained older individuals were enrolled, and later allocated to groups according to BMI categories (normal [≤ 24.9 kg/m²], overweight [25 to 29.9 kg/m²] and obese [≥ 30 kg/m²]). Sixty-four active/trained older individuals were enrolled, and later allocated to groups according to BMI categories (normal [≤ 24.9 kg/m²], overweight [25 to 29.9 kg/m²] and obese [≥ 30 kg/m²]). Assessments were conducted in two separate visits to the laboratory. In the first visit, participants underwent measures of height, body mass, and peak torque leg extension and flexion using an isokinetic dynamometer. On visit two, participants performed the 30-second Sit and Stand test (30SST), Timed Up and Go (TUG), and 6-minute Walk (6MW) tests. ANOVA one-way was used to analyze the data and significance was set at P < .05. One-way ANOVAs did not reveal significance differences among BMI categories for leg extension peak torque (F(2,61) = 1.11; P = 0.336), leg flexion peak torque (F(2,61) = 1.22; P = 0.303), 30SST (F(2,61) =1.28; P = 0.285), TUG (F(2,61) = 0.238; P = 0.789), and 6MW (F(2,61) = 2.52; P = 0.089)]. Our findings indicated that for older individuals who exercise regularly, physical function tests which mimic ordinary activities of daily living, are not impacted by BMI status. Thus, being physically active may counteract some of the negative effects of high BMI observed in the older adult population.

The Impact of COVID-19-Related Shutdown Measures on the Training Habits and Perceptions of Athletes in the United States: A Brief Research Report

The purpose of the current study was to examine the impact of COVID-19 government-enforced shutdown measures on the training habits and perceptions of athletes. A web-based electronic survey was developed and distributed online to athletes. The survey contained questions regarding currently available resources, changes in weekly training habits, and perceptions of training such as intensity, motivation, and enjoyment. A total of 105 (males: n = 31; females: n = 74) athletes completed the survey (mean ± SD age = 19.86 ± 2.13 years). Ninety-nine (94.3%) athletes continued to receive guidance from their primary sport coach or strength training staff. There was a significant (p < 0.001) decrease (mean ± SD) in self-reported participation time for strength training (-1.65 ± 4.32 h. week^-1), endurance (-1.47 ± 3.93 h. week^-1), and mobility (-1.09 ± 2.24 h. week^-1), with the largest reduction coming from participation time in sport-specific activities (-6.44 ± 6.28 h. week^-1) pre- to post-shutdown. When asked to rate their current state of emotional well-being using a visual analog scale of 0-100, with 100 being exceptional, the mean score was 51.6 ± 19.6 AU. Athletes experienced notable reductions in training frequency and time spent completing various training related activities. In the future, practitioners should have preparations in place in the event of another lockdown period or future pandemic to avoid or minimize significant disruptions in training. Special considerations may be needed when athletes are allowed to return to sport in the event of significant levels of detraining that may have occurred.

Comparison of Multi-Frequency Bioelectrical Impedance and Dual-Energy X-Ray Absorptiometry to Assess Body Composition in College-Aged Adults

The purpose of this study was to evaluate the validity of whole body percent fat (%BF) and segmental fat-free mass (FFM) using multi-frequency bioelectrical impedance analysis (MF-BIA) and dual-energy x-ray absorptiometry (DEXA) in college-aged adults. Sixty-two participants male (n = 32) and female (n = 30) completed MF-BIA and DEXA measurements following established pre-test guidelines. %BF and segmental FFM (right arm, left arm, trunk, right leg, and left leg) were collected and analyzed. The MF-BIA significantly (p < 0.05) underestimated %BF for all participants, females, and males compared to DEXA. In addition, MF-BIA significantly (p < 0.05) underestimated FFM in the arms and legs in all participants and males with the exception of the left arm in all subjects while significantly overestimating FFM in the trunk. In females, the MF-BIA overestimated FFM in the arms and trunk while significantly (p < 0.05) underestimating FFM in the legs. Difference plots also indicated that the underestimation of FFM from MF-BIA in the arms and legs increased as the amount of FFM increased. Thus, our findings suggested that the MF-BIA may not be accurate for measuring whole %BF and segmental FFM in the college-aged population.

Application of the neuromuscular fatigue threshold treadmill test to muscles of the quadriceps and hamstrings

PURPOSE

The purposes of the present study were: (1) to determine whether the physical working capacity at the fatigue threshold (PWC_FT) model that has been used for estimating the onset of neuromuscular fatigue in the vastus lateralis (VL) during incremental treadmill running could also be applied to the vastus medialis (VM), biceps femoris (BF), and semitendinosus (ST) muscles; and (2) if applicable, to compare the running velocities associated with the PWC_FT among these muscles.

METHODS

Eleven subjects (age 21.7 ± 1.8 years) performed an incremental treadmill test to exhaustion with electromyographic signals recorded from the VL, VM, BF, and ST.

RESULTS

The results indicated there were no significant (p > 0.05) mean differences in the running velocities associated with the PWC_FT for the VL (14.4 ± 2.0 km/h), VM (14.3 ± 1.9 km/h), BF (13.8 ± 1.8 km/h), and ST (14.7 ± 2.3 km/h). In addition, there were significant inter-correlations (r = 0.68-0.88) among running velocities associated with the PWC_FT of each muscle. Individual results also indicated that 9 of the 11 subjects exhibited identical PWC_FT values for at least 3 of the 4 muscles, but there were no uniform patterns for any intra-individual differences.

CONCLUSION

The findings of the present study suggested that the PWC_FT test is a viable method to identify neuromuscular fatigue in the quadriceps and hamstrings during incremental treadmill exercise and results in consistent PWC_FT values among these muscles.

Effects of a Multi-Ingredient Preworkout Supplement Versus Caffeine on Energy Expenditure and Feelings of Fatigue during Low-Intensity Treadmill Exercise in College-Aged Males

The primary purpose of this study was to examine the acute effects of a multi-ingredient (i.e., caffeine, green tea extract, Yohimbe extract, capsicum annum, coleus extract, L-carnitine, beta-alanine, tyrosine) preworkout supplement versus a dose of caffeine (6 mg·kg⁻¹) on energy expenditure during low-intensity exercise. The effects of these treatments on substrate utilization, gas exchange, and psychological factors were also investigated. Twelve males (mean ± SD: age = 22.8 ± 2.4 years) completed three bouts of 60 min of treadmill exercise on separate days after consuming a preworkout supplement, 6 mg·kg⁻¹ of caffeine, or placebo in a randomized fashion. The preworkout and caffeine supplements resulted in significantly greater energy expenditure (p < 0.001, p = 0.006, respectively), V˙O₂ (p < 0.001, p = 0.007, respectively), V˙CO₂ (p = 0.006, p = 0.049, respectively), and V˙_E (p < 0.001, p = 0.007, respectively) compared to placebo (collapsed across condition). There were no differences among conditions, however, for rates of fat or carbohydrate oxidation or respiratory exchange ratio. In addition, the preworkout supplement increased feelings of alertness (p = 0.015) and focus (p = 0.005) 30-min postingestion and decreased feelings of fatigue (p = 0.014) during exercise compared to placebo. Thus, the preworkout supplement increased energy expenditure and measures of gas exchange to the same extent as 6 mg·kg⁻¹ of caffeine with concomitant increased feelings of alertness and focus and decreased feelings of fatigue.

The accuracy of fitness watches for the measurement of heart rate and energy expenditure during moderate intensity exercise

BACKGROUND

As new technology emerges and updated fitness watches are released to the market, it is important to examine their accuracy. The aim of the current study was to examine the accuracy of three commercially available activity trackers in assessing heart rate (HR) and energy expenditure (EE) during moderate intensity exercise.

METHODS

Twenty healthy participants (Age: 20.5±0.7 yrs., Ht: 173.4±10.8 cm, BM: 72.8±13.9 kg, BMI: 24.0±2.5 kg/m²) wore two fitness watches (FB: Fitbit Versa^TM, San Francisco, CA, USA; and PI: Polar Ignite^TM, Polar Electro Oy, Kempele, Finland) and a chest-worn HR monitor (PTP: Polar TeamPro Sensor^TM, Polar Electro) during a 12-minute exercise protocol at incremental speeds. An electrocardiogram (ECG) and indirect calorimetry were used as criterion measures for HR and EE. Mean absolute percentage error (MAPE) was calculated to determine measurement error.

RESULTS

The MAPE values for HR were 11.6±8.7% for the FB, 11.0±10.0% for the PI, and 6.3±5.2% for the PTP. For EE, MAPE values were 9.6±7.2% for the FB, 16.7±19.6% for the PI and 13.8±13.0% for the PTP.

CONCLUSIONS

Fitness watches relying on optical measures of HR underestimate HR compared to criterion measures during moderate intensity exercise. Despite providing a more accurate measure of HR, a chest-worn monitor does not provide a more accurate estimate of EE compared to fitness watches. The Fitbit provided the most accurate measure of EE when compared to the Polar Ignite watch and chest-worn device.

Acute Effects of a Multi-Ingredient Pre-Workout Supplement On 5-KM Running Performance in Recreationally-Trained Athletes

The purpose of the present study was to examine the effects of an acute dose of a multi-ingredient pre-workout supplement on 5-km running performance and subjective measures of fatigue. Twenty aerobically-trained, males (n = 10, mean ± SD = 80.8 ± 6.1 kg) and females (n = 10, 64.5 ± 6.6 kg) completed two 5-km running races for time in a double-blind, cross-over fashion. During the first session, subjects were randomly assigned to ingest the supplement or placebo 30 minutes prior to running a 5-km race. The supplement contained multiple ingredients including caffeine anhydrous (150 mg), beta alanine (1.6 g), and arginine alpha-ketoglutarate (AKG) (1.0 g). Subjects also completed a 5-point Likert scale (1 = low, 5 = high) questionnaire to determine feelings of fatigue immediately prior to ingesting the substance (baseline), 30 minutes post-ingestion (immediately pre-race), and 5 minutes post-race. For the second session, subjects ingested the opposite substance (supplement or placebo) and underwent the same testing procedures (including time of day) as the first session. The results indicated there was no significant (p > 0.05) difference in 5-km race time between the supplement (23.62 ± 2.08 min) and placebo (23.51 ± 1.97 min) conditions. For the feelings of fatigue, there were no significant condition × time interactions or main effects for condition, but there were main effects for time. These findings indicated that the pre-workout supplement provided no ergogenic effect on 5-km race time or subjective feelings of fatigue when administered on an acute basis in aerobically-trained individuals.

Supplementation with a Multi-ingredient Pre-workout Supplement does not Augment Resistance Training Adaptations in Females

Multiple ingredient pre-workout supplements (MIPS) are purported to offer favorable acute metabolic changes potentially leading to improvements in body composition and training adaptations over time. However, there is limited information available regarding the long-term benefits and safety of consuming MIPS, specifically in female populations. Therefore, the purpose of this study was to investigate the effects of pre-workout ingestion on body composition, training adaptations and select markers of clinical health in recreationally active females after 7 weeks of supplementation and resistance training. Nineteen participants participated in a randomized, double-blind, placebo controlled study. Experimental testing included resting heart rate and blood pressure, blood lipid panels, body composition, resting metabolic testing and performance measurements before and after a seven-week resistance training program while ingesting either a MIPS or placebo once daily. There were no significant group x time interactions for changes in body fat percentage (p=0.66), fat-free mass (p=0.87), fat mass (p=0.63) or resting metabolic rate (p=0.52). Both groups showed significant improvements in upper (p<0.001) and lower body (p<0.001) maximal strength following the 7-week training period however no differences in upper (p=0.74) and lower body (p=0.53) strength improvements were observed between groups, respectively. No significant group x time interactions were observed for any of the markers of clinical health. In conclusion, the current study suggests that daily consumption of a MIPS does not enhance training adaptations in recreationally active females and does not appear to negatively affect resting blood pressure, heart rate and blood lipids.

Validity and reliability of a handheld blood glucose monitor during exercise and an oral glucose tolerance test

The purpose of the present study was to examine the validity and reliability of the handheld Nova Max Plus blood glucose monitor during an oral glucose tolerance test and 60-minute bout of exercise. Thirty subjects (mean age±SD=22.3±1.9 years; body mass=77.6±14.2 kg) volunteered for an oral glucose tolerance test or 60-minute treadmill test. Blood glucose concentrations were measured from the fingertip at six time points during both tests. The reference method of blood glucose analysis was the Yellow Springs Instruments (YSI) 2300. Our results indicated that the blood glucose values provided by the Nova Max Plus were significantly (p&lt;.05) greater than the YSI 2300 at all-time points of the oral glucose tolerance test and treadmill test. In addition, the Nova Max Plus exhibited an overall mean absolute relative deviation (±SD) of 9.0 (±7.0) and did not meet the 95% accuracy requirements of ISO 15197:2013. The Bland-Altman plot for constant error (YSI 2300 – Nova Max Plus) versus the reference method (YSI 2300) indicated an average negative bias (-8.2 mg·dL-1) that increased (r=-0.23) at higher blood glucose values. Intra-device reliability analyses for the Nova Max Plus demonstrated the ICC was R=0.99 and CV=3.0%, with no mean differences between the test and retest values. These findings suggested that the Nova Max Plus provided highly reliable, yet inaccurate blood glucose values compared to the YSI 2300 during the dynamic conditions associated with an oral glucose tolerance test and exercise.

Accuracy of Resting Metabolic Rate Prediction Equations in Athletes

Jagim, AR, Camic, CL, Kisiolek, J, Luedke, J, Erickson, J, Jones, MT, and Oliver, JM. Accuracy of resting metabolic rate prediction equations in athletes. J Strength Cond Res 32(7): 1875-1881, 2018-The purpose of this study was to determine the accuracy of 5 different resting metabolic rate (RMR) prediction equations in male and female athletes. Twenty-two female (19.7 ± 1.4 years; 166.2 ± 5.5 cm; 63.5 ± 7.3 kg; 49.2 ± 4.3 kg of fat-free mass (FFM); 23.4 ± 4.4 body fat (BF) percent) and 28 male (20.2 ± 1.6 years; 181.9 ± 6.1 cm; 94.5 ± 16.2 kg; 79.1 ± 7.2 kg of FFM; 15.1 ± 8.5% BF) athletes were recruited to participate in 1 day of metabolic testing. Assessments comprised RMR measurements using indirect calorimetry, and body composition analyses using air displacement plethysmography. One-way repeated-measures analysis of variance with follow-up paired t tests were selected to determine differences between indirect calorimetry and 5 RMR prediction equations. Linear regression analysis was used to assess the accuracy of each RMR prediction method. An alpha level of p ≤ 0.05 was used to determine statistical significance. All the prediction equations significantly underestimated RMR while the Cunningham equation had the smallest mean difference (-165 kcals). In men, the Harris-Benedict equation was found to be the best prediction formula with the lowest root-mean-square prediction error value of 284 kcals. In women, the Cunningham equation was found to be the best prediction equation with the lowest root-mean-squared error value of 110 kcals. Resting metabolic rate prediction equations consistently seem to underestimate RMR in male and female athletes. The Harris-Benedict equation seems to be most accurate for male athletes, whereas the Cunningham equation may be better suited for female athletes.

Sex Differences in Resting Metabolic Rate Among Athletes

Jagim, AR, Camic, CL, Askow, A, Luedke, J, Erickson, J, Kerksick, CM, Jones, MT, and Oliver, JM. Sex differences in resting metabolic rate among athletes. J Strength Cond Res 33(11): 3008-3014, 2019-The purpose of this study was to compare differences in resting metabolic rate (RMR) between sexes in Division III National Collegiate Athletic Association (NCAA) collegiate athletes and to identify predictors of RMR. Sixty-eight male (M) (age: 20.1 ± 1.5 years; height: 181.8 ± 5.9 cm; body mass (BM): 93.7 ± 16.3 kg; and body fat%: 16.3 ± 8.6%) and 48 female (F) athletes (age: 19.4 ± 1.3 years; height: 166.5 ± 6.0 cm; BM: 63.4 ± 12.7 kg; and body fat%: 21.5 ± 6.3%) participated in a single day of testing, which included determination of RMR using indirect calorimetry and air displacement plethysmography to measure fat mass and fat-free mass (FFM). An independent-samples t-test was used to compare differences in body composition and RMR between sexes, and regression analysis was used to identify predictors of RMR. Men had a significantly higher absolute RMR (M: 2,481 ± 209 vs. F: 1,553 ± 193 kcals·d; p < 0.001), but when adjusted for BM (M: 25.6 ± 8.3 vs. F: 25.9 ± 2.5 kcals·kg BM per day; p = 0.82) and FFM (M: 31.1 ± 10.6 vs. F: 33.6 ± 3.8 kcals·kg FFM per day; p = 0.12), these differences became nonsignificant. Regression analysis indicated that BM in both men (β = 0.73) and women (β = 0.88) was the strongest predictor of RMR. The results of the current study indicate minimal differences in RMR between sexes among athletic populations when adjusted for BM and FFM. In the current group of athletes, BM seems to account for the largest variability in RMR.

Acute Effects of the Elevation Training Mask on Strength Performance in Recreational Weight lifters

Jagim, AR, Dominy, TA, Camic, CL, Wright, G, Doberstein, S, Jones, MT, and Oliver, JM. Acute effects of the elevation training mask on strength performance in recreational weightlifters. J Strength Cond Res 32(2): 482-489, 2018-The Elevation Training Mask 2.0 (ETM) is a novel device that purportedly simulates altitude training. The purpose of this study was to investigate the acute effects of the ETM on resistance exercise performance, metabolic stress markers, and ratings of mental fatigue. Twenty male recreational weight lifters completed 2 training sessions of back squat and bench press (6 sets of 10 repetitions at 85% of 5-repetition maximum and seventh set to failure) as well as a maximal effort sprint test (18% body mass) with the mask (ETM) and without the mask (NM). Training evaluation included baseline and postexercise blood lactate and oxygen saturation measures. Performance evaluation included peak and average velocity bar velocity, total volume load, total work, total repetitions completed, and sprint performance. Adverse side effects were reported in 12% (n = 3) of participants, which included feelings of light headedness, anxiety, and discomfort. No differences were found in repetitions or total workload in back squat (p = 0.07) or bench press (p = 0.08) between conditions. A lower peak velocity was identified during the back squat, bench press, and sprint test in the ETM condition (p = 0.04). Blood lactate values were lower after bench press and sprint during the ETM condition (p < 0.001). Significantly lower ratings of alertness and focus for task were found after squat, bench press, and sprint test in the ETM condition compared with the NM condition (p < 0.001). Wearing the ETM during bouts of resistance training did not hinder the ability to achieve desired training volumes during the resistance training session. However, wearing the ETM does seem to attenuate the ability to maintain working velocity during training bouts and negatively influence ratings of alertness and focus for task.

Velocity-Dependent Changes in Electrical Efficiency of the Leg Extensors during Eccentric Isokinetic Muscle Actions

The mechanisms underlying velocity-specific decreases in torque production during eccentric muscle actions remain unclear. Therefore, the purpose of the present study was to examine electrical efficiency at 60 and 180°·s -1 during fatiguing, maximal eccentric isokinetic muscle actions of the leg extensors. Thirteen men visited the lab on two occasions and randomly performed 30 repeated maximal eccentric isokinetic muscle actions of the leg extensors at 60 and 180°·s - ¹ through a 90° range of motion. Polynomial regression analyses and separate repeated measures ANOVAs were used to examine the composite patterns of responses for electromyographic amplitude, eccentric torque, and electrical efficiency across the 60 and 180°·s - ¹ protocols. Eccentric torque remained unchanged across the 30 maximal eccentric muscle actions performed at 60 and 180°·s -1. Electromyographic amplitude and electrical efficiency, however, increased linearly across the 180°·s -1 protocol, but there were no changes for either electromyographic amplitude or electrical efficiency during the 60°·s -1 fatiguing protocol. These findings indicated that performing eccentric muscle actions at a fast velocity (i. e., 180°·s -1) was characterized by greater efficiency (i. e., decreased electrical efficiency) compared to eccentric muscle actions performed at a slow velocity (i. e., 60°·s -1). Thus, it is possible that eccentric muscle actions performed at fast velocities are more robust to fatigue due, in part, to greater efficiency compared to slow-velocity eccentric muscle actions.

The acute effects of a multi-ingredient pre-workout supplement on resting energy expenditure and exercise performance in recreationally active females

BACKGROUND

The use of dietary supplements to improve performance is becoming increasingly popular among athletes and fitness enthusiasts. Unfortunately, there is a tremendous lack of research being done regarding female athletes and the use of sport supplements. The purpose of this study was to examine the acute effects of multi-ingredient pre-workout supplement (MIPS) ingestion on resting metabolism and exercise performance in recreationally-active females.

METHODS

Fifteen recreationally-active females participated in a randomized, double-blind, placebo controlled study. Subjects completed baseline, and two experimental testing sessions in a cross-over design fashion. Experimental testing included assessment of resting energy expenditure (REE), heart rate, and blood pressure following the ingestion of a MIPS or placebo. Subjects also completed a repetition to failure test for the back squat (BS) and bench press (BP) at 85% of their 5-repetition maximum followed by the assessment of anaerobic power using a counter-movement vertical jump test and a sprint test on a force-treadmill. Subjective measurements of energy, focus, and fatigue were also assessed using a 5-point Likert scale. Separate repeated measures analysis of variance (ANOVA) were used to assess differences in REE, cardiovascular responses, and subjective markers between conditions. Performance data were analyzed using paired Student's T-tests.

RESULTS

A significant main effect for condition was observed for REE (p = 0.021) and diastolic blood pressure (p = 0.011) following ingestion of the MIPS. The supplement condition resulted in a greater number of BP repetitions to failure and total work completed during treadmill test (p = 0.039) compared to placebo (p = 0.037). A significant condition x time interaction for focus was observed with the supplement treatment exhibiting improved focus at 80-min post ingestion (p = 0.046).

CONCLUSIONS

Consumption of a MIPS increased resting metabolism following a single dose accompanied by an increase in diastolic blood pressure. Furthermore, acute MIPS ingestion improved upper body muscular endurance and anaerobic capacity while improving feelings of focus following high-intensity exercise in recreationally active females.

Validation of the physical working capacity at the fatigue threshold treadmill test

<div>The purposes of the present study were twofold: 1) to determine the physical working capacity at the fatigue threshold (PWCFT) during an incremental treadmill test, and 2) to examine the validity of this fatigue threshold through constant-velocity runs to exhaustion at 90, 100, and 110% of the estimated PWCFT. Twelve aerobically-trained males (mean age±SD=24.6±5.4 years, running volume=69.9±46.0 km·wk-1, n=9) and females (22.3±2.3 years, 45.6±4.6 km·wk-1, n=3) volunteered to perform a treadmill test to exhaustion with electromyographic (EMG) signals recorded from the m. vastus lateralis on four separate visits. The First visit required each subject to complete an incremental treadmill test to exhaustion for determination of their PWCFT. During the second, third, and fourth visit, the subjects completed a treadmill run to exhaustion at a constant velocity that corresponded to 90, 100, or 110% of their PWCFT in random order. The linear regression analyses indicated there were no significant (p&gt;.05) changes in muscle activation (i.e. EMG amplitude) across time to exhaustion during the constant velocity runs at 90% (60.00±0.00 min) and 100% (48.86±14.59 min) PWCFT, but significant (p&lt;.05) increases occurred at 110% PWCFT (19.44±10.26 min). Thus, the findings of the present study indicated that the PWCFT treadmill test was able to accurately estimate the fastest running velocity that could be maintained for an extended period of time without evidence of neuromuscular fatigue.</div>

Influences of Interelectrode Distance and Innervation Zone on Electromyographic Signals

The purpose of the present study was to examine the effects of electrode placements centered over and offset from the innervation zone (IZ) with different interelectrode distances (IED) on the time and frequency domain parameters of the electromyographic (EMG) signal during a fatiguing submaximal, isometric workout. 11 adults performed an isometric leg extension muscle action at 50% maximal voluntary isometric contraction (MVIC) to exhaustion. Electromyographic amplitude and frequency parameters were determined from electrode placements with different IED centered over, at proximal offset, at distal offset, and away from the IZ at 10, 50, and 100% of the time to exhaustion using an electrode array. There were greater absolute EMG amplitude and lower absolute EMG frequency for electrode placements over and offset from the IZ, but lower absolute EMG amplitude over than offset from the IZ regardless of IED at each time-point during the time to exhaustion. The absolute EMG frequency values were affected by the location relative to the IZ and IED of the electrode placements, and were greater for distal offset vs. proximal offset electrode placements at each time-point. Normalization of the EMG amplitude and EMG frequency values to MVIC eliminated differences due to IED and electrode placements during the fatiguing workout.

Time Course of Changes in Neuromuscular Parameters During Sustained Isometric Muscle Actions

Smith, CM, Housh, TJ, Herda, TJ, Zuniga, JM, Camic, CL, Bergstrom, HC, Smith, DB, Weir, JP, Hill, EC, Cochrane, KC, Jenkins, NDM, Schmidt, RJ, and Johnson, GO. Time course of changes in neuromuscular parameters during sustained isometric muscle actions. J Strength Cond Res 30(10): 2697-2702, 2016-The objective of the present study was to identify the time course of changes in electromyographic (EMG) and mechanomyographic (MMG) time and frequency domain parameters during a sustained isometric muscle action of the leg extensors at 50% maximal voluntary isometric contraction. The EMG and MMG signals were measured from the vastus lateralis of 11 subjects to identify when motor unit activation strategies changed throughout the sustained isometric muscle action. The EMG amplitude (muscle activation) had a positive linear relationship (p = 0.018, r = 0.77) that began to increase at the initiation of the muscle action and continued until task failure. Electromyographic frequency (motor unit action potential conduction velocity) and MMG frequency (global motor unit firing rate) had negative quadratic relationships (p = 0.002, R = 0.99; p = 0.015, R = 0.94) that began to decrease at 30% of the time to exhaustion. The MMG amplitude (motor unit activation) had a cubic relationship (p = 0.001, R = 0.94) that increased from 10 to 30% of the time to exhaustion, then decreased from 40 to 70% of the time to exhaustion, and then markedly increased from 70% to task failure. The time course of changes in the neuromuscular parameters suggested that motor unit activation strategies changed at approximately 30 and 70% of the time to exhaustion during the sustained isometric muscle action. These findings indicate that the time course of changes in neuromuscular responses provide insight into the strategies used to delay the effects of fatigue and are valuable tools for quantifying changes in the fatiguing process during training programs or supplementation research.

Electromyographic Responses from the Vastus Medialis during Isometric Muscle Actions

This study examined the electromyographic (EMG) responses from the vastus medialis (VM) for electrodes placed over and away from the innervation zone (IZ) during a maximal voluntary isometric contraction (MVIC) and sustained, submaximal isometric muscle action. A linear electrode array was placed on the VM to identify the IZ and muscle fiber pennation angle during an MVIC and sustained isometric muscle action at 50% MVIC. EMG amplitude and frequency parameters were determined from 7 bipolar channels of the electrode array, including over the IZ, as well as 10 mm, 20 mm and 30 mm proximal and distal to the IZ. There were no differences between the channels for the patterns of responses for EMG amplitude or mean power frequency during the sustained, submaximal isometric muscle action; however, there were differences between channels during the MVIC. The results of the present study supported the need to standardize the placement of electrodes on the VM for the assessment of EMG amplitude and mean power frequency. Based on the current findings, it is recommended that electrode placements be distal to the IZ and aligned with the muscle fiber pennation angle during MVICs, as well as sustained, submaximal isometric muscle actions.

Evidence that the talk test can be used to regulate exercise intensity

The Talk Test (TT) has been shown to be a surrogate of the ventilatory threshold and to be a viable alternative to standard methods of prescribing exercise training intensity. The TT has also been shown to be responsive to manipulations known to change physiologic function including blood donation and training. Whether the TT can be used independently to regulated training intensity is not known. Physically active volunteers (N = 16) performed an incremental exercise test to identify stages of the TT (Last Positive [LP], Equivocal [EQ], and Negative [NEG]). In subsequent, randomly ordered, 30-minute steady-state runs, the running velocity was regulated solely by "clamping" the TT response desired and then monitoring the response of conventional markers of exercise intensity (heart rate, blood lactate, rating of perceived exertion). All subjects were able to complete the LP stage, but only 13 of 16 and 2 of 16 subjects were able to complete the EQ and NEG stages, respectively. Physiologic responses were broadly within those predicted from the incremental exercise test and within the appropriate range of physiologic responses for exercise training. Thus, in addition to correlating with convenient physiological markers, the TT can be used proactively to guide exercise training intensity. The LP stage produced training intensities compatible with appropriate training intensity in healthy adults and with recovery sessions or long duration training sessions in athletes. The EQ and NEG stages produced intensities compatible with higher intensity training in athletes. The results demonstrate that the TT can be used as a primary method to control exercise training intensity.

Effects of the innervation zone on the time and frequency domain parameters of the surface electromyographic signal

The purposes of the present study were to examine the effects of electrode placements over, proximal, and distal to the innervation zone (IZ) on electromyographic (EMG) amplitude (RMS) and frequency (MPF) responses during: (1) a maximal voluntary isometric contraction (MVIC), and; (2) a sustained, submaximal isometric muscle action. A linear array was used to record EMG signals from the vastus lateralis over the IZ, 30mm proximal, and 30mm distal to the IZ during an MVIC and a sustained isometric muscle action of the leg extensors at 50% MVIC. During the MVIC, lower EMG RMS (p>0.05) and greater EMG MPF (p<0.05) values were recorded over the IZ compared to away from the IZ, however, no differences in slope coefficients for the EMG RMS and MPF versus time relationships over, proximal, and distal to the IZ occurred. Thus, the results of the present study indicated that during an MVIC, EMG RMS and MPF values recorded over the IZ are not comparable to those away from the IZ. However, the rates of fatigue-induced changes in EMG RMS and MPF during sustained, submaximal isometric muscle actions of the leg extensors were the same regardless of the electrode placement locations relative to the IZ.

The influence of electromyographic recording methods and the innervation zone on the mean power frequency-torque relationships

This study examined the effects of electromyographic (EMG) recording methods and innervation zone (IZ) on the mean power frequency (MPF)-torque relationships. Nine subjects performed isometric ramp muscle actions of the leg extensors from 5% to 100% of maximal voluntary contraction with an eight channel linear electrode array over the IZ of the vastus lateralis. The slopes were calculated from the log-transformed monopolar and bipolar EMG MPF-torque relationships for each channel and subject and 95% confidence intervals (CI) were constructed around the slopes for each relationship and the composite of the slopes. Twenty-two to 55% of the subjects exhibited 95% CIs that did not include a slope of zero for the monopolar EMG MPF-torque relationships while 25-75% of the subjects exhibited 95% CIs that did not include a slope of zero for the bipolar EMG MPF-torque relationships. The composite of the slopes from the EMG MPF-torque relationships were not significantly different from zero for any method or channel, however, the method and IZ location slightly influenced the number of significant slopes on a subject-by-subject basis. The log-transform model indicated that EMG MPF-torque patterns were nonlinear regardless of recording method or distance from the IZ.

Acute effects of an arginine-based supplement on neuromuscular, ventilatory, and metabolic fatigue thresholds during cycle ergometry

The purpose of the present study was to examine the effects of an acute dose of an arginine-based supplement on the physical working capacity at the fatigue threshold (PWCFT), lactate threshold (LT), ventilatory threshold (VT), and peak oxygen uptake during incremental cycle ergometry. This study used a double-blinded, placebo-controlled, within-subjects crossover design. Nineteen untrained men (mean age ± SD = 22.0 ± 1.7 years) were randomly assigned to ingest either the supplement (3.0 g of arginine, 300 mg of grape seed extract, and 300 mg of polyethylene glycol) or placebo (microcrystalline cellulose) and performed an incremental test on a cycle ergometer for determination of PWCFT, LT, VT, and peak oxygen uptake. Following a 1-week period, the subjects returned to the laboratory and ingested the opposite substance (either supplement or placebo) prior to completing another incremental test to be reassessed for PWCFT, LT, VT, and peak oxygen uptake. The paired-samples t tests indicated there were significant (P < 0.05) mean differences between the arginine and placebo conditions for the PWCFT (192 ± 42 vs. 168 ± 53 W, respectively) and VT (2546 ± 313 vs. 2452 ± 342 mL·min(-1)), but not the LT (135 ± 26 vs. 138 ± 22 W), absolute peak oxygen uptake (3663 ± 445 vs. 3645 ± 438 mL·min(-1)), or relative peak oxygen uptake (46.5 ± 6.0 vs. 46.2 ± 5.0 mL·kg(-1)·min(-1)). These findings suggested that the arginine-based supplement may be used on an acute basis for delaying the onset of neuromuscular fatigue (i.e., PWCFT) and improving the VT in untrained individuals.

The effects of polyethylene glycosylated creatine supplementation on anaerobic performance measures and body composition

The purpose of this study was to examine the effects of 28 days of polyethylene glycosylated creatine (PEG-creatine) supplementation (1.25 and 2.50 g·d) on anaerobic performance measures (vertical and broad jumps, 40-yard dash, 20-yard shuttle run, and 3-cone drill), upper- and lower-body muscular strength and endurance (bench press and leg extension), and body composition. This study used a randomized, double-blind, placebo-controlled parallel design. Seventy-seven adult men (mean age ± SD, 22.1 ± 2.5 years; body mass, 81.7 ± 10.8 kg) volunteered to participate and were randomly assigned to a placebo (n = 23), 1.25 g·d of PEG-creatine (n = 27), or 2.50 g·d of PEG-creatine (n = 27) group. The subjects performed anaerobic performance measures, muscular strength (one-repetition maximum [1RM]), and endurance (80% 1RM) tests for bench press and leg extension, and underwater weighing for the determination of body composition at day 0 (baseline), day 14, and day 28. The results indicated that there were improvements (p < 0.0167) in vertical jump, 20-yard shuttle run, 3-cone drill, muscular endurance for bench press, and body mass for at least one of the PEG-creatine groups without changes for the placebo group. Thus, the present results demonstrated that PEG-creatine supplementation at 1.25 or 2.50 g·d had an ergogenic effect on lower-body vertical power, agility, change-of-direction ability, upper-body muscular endurance, and body mass.

An electromyographic-based test for estimating neuromuscular fatigue during incremental treadmill running

The purposes of the present study were two fold: (1) to determine if the model used for estimating the physical working capacity at the fatigue threshold (PWCFT) from electromyographic (EMG) amplitude data during incremental cycle ergometry could be applied to treadmill running to derive a new neuromuscular fatigue threshold for running, and (2) to compare the running velocities associated with the PWCFT, ventilatory threshold (VT), and respiratory compensation point (RCP). Fifteen college-aged subjects (21.5 ± 1.3 y, 68.7 ± 10.5 kg, 175.9 ± 6.7 cm) performed an incremental treadmill test to exhaustion with bipolar surface EMG signals recorded from the vastus lateralis. There were significant (p < 0.05) mean differences in running velocities between the VT (11.3 ± 1.3 km h(-1)) and PWCFT (14.0 ± 2.3 km h(-1)), VT and RCP (14.0 ± 1.8 km h(-1)), but not the PWCFT and RCP. The findings of the present study indicated that the PWCFT model could be applied to a single continuous, incremental treadmill test to estimate the maximal running velocity that can be maintained prior to the onset of neuromuscular fatigue. In addition, these findings suggested that the PWCFT, like the RCP, may be used to differentiate the heavy from severe domains of exercise intensity.