TEST-RETEST RELIABILITY FOR VOLUNTARY AND EVOKED MEASURES OF PEAK TORQUE, ELECTROMECHANICAL DELAY, AND RATE OF TORQUE DEVELOPMENT IN OLDER MEN.

The purpose of this study was to examine the test-retest reliability for peak torque (PT), rates of torque development (RTD), and electromechanical delay (EMD) calculated during voluntary and evoked muscle actions in men ages 65 and older. Fifteen older men (mean ± standard deviation (SD) age = 72.3 ± 7.3 years) completed 3 evoked and 3 voluntary isometric muscle actions of the leg extensors during two visits separated by 48 to 72 h. PT and EMD were calculated during voluntary and evoked muscle actions. RTD was quantified as the peak RTD, overall RTD, RTD in time intervals of 0-30 (RTD30), 0-50 (RTD50), 0-100 (RTD100), and 0-200 ms (RTD200) from the onset of torque, and RTD in 10 ms epochs during the first 250 ms after the onset of torque or to peak torque for voluntary and evoked muscle actions. Intraclass correlation coefficients (ICCs), standard errors of measurement (SEMs), and coefficients of variation (CV) were used to quantify the test-retest reliability. Voluntary and evoked PT demonstrated good reliability, whereas EMD can be considered unreliable. The ICCs for voluntary PRTD, RTD30, RTD50, RTD100, RTD200, and overall RTDranged from 0.598-0.799, while for evoked PRTD, RTD30,RTD50, RTD100, and overall RTD, ICCs ranged from 0.943-0.984. Voluntary RTDs in 10 ms epochs had ICCs ranging from 0.179-0.939, while evoked RTD in 10 ms epochs demonstrated ICCs ranging from 0.693-0.975. Except for PRTD and RTD in 10 ms epochs after 50 ms, CVs were higher for voluntary (11-41%) than evoked (7-24%) measures. Systematic decreases occurred from trial one to trial two for several voluntary measures of RTD, while there was only one for the evoked measures of RTD. CONCLUSIONS: There is dissociation in the reliability of voluntary and evoked PT, and RTD, such that the evoked measurements display greater reliability in older men. Voluntary RTDs were most suspect, consistently demonstrating lower ICCs and greater SEMs than evoked RTD. However, if choosing to measure voluntary RTD in older men, the most reliable measurements may be RTD in the first 10 ms, 80-110 ms, or overall RTD. Finally, EMD may be unreliable in older men. Adviser: Joel T. Crame

TEST-RETEST RELIABILITY FOR VOLUNTARY AND EVOKED MEASURES OF PEAK TORQUE, ELECTROMECHANICAL DELAY, AND RATE OF TORQUE DEVELOPMENT IN OLDER MEN.

The purpose of this study was to examine the test-retest reliability for peak torque (PT), rates of torque development (RTD), and electromechanical delay (EMD) calculated during voluntary and evoked muscle actions in men ages 65 and older. Fifteen older men (mean ± standard deviation (SD) age = 72.3 ± 7.3 years) completed 3 evoked and 3 voluntary isometric muscle actions of the leg extensors during two visits separated by 48 to 72 h. PT and EMD were calculated during voluntary and evoked muscle actions. RTD was quantified as the peak RTD, overall RTD, RTD in time intervals of 0-30 (RTD30), 0-50 (RTD50), 0-100 (RTD100), and 0-200 ms (RTD200) from the onset of torque, and RTD in 10 ms epochs during the first 250 ms after the onset of torque or to peak torque for voluntary and evoked muscle actions. Intraclass correlation coefficients (ICCs), standard errors of measurement (SEMs), and coefficients of variation (CV) were used to quantify the test-retest reliability. Voluntary and evoked PT demonstrated good reliability, whereas EMD can be considered unreliable. The ICCs for voluntary PRTD, RTD30, RTD50, RTD100, RTD200, and overall RTDranged from 0.598-0.799, while for evoked PRTD, RTD30,RTD50, RTD100, and overall RTD, ICCs ranged from 0.943-0.984. Voluntary RTDs in 10 ms epochs had ICCs ranging from 0.179-0.939, while evoked RTD in 10 ms epochs demonstrated ICCs ranging from 0.693-0.975. Except for PRTD and RTD in 10 ms epochs after 50 ms, CVs were higher for voluntary (11-41%) than evoked (7-24%) measures. Systematic decreases occurred from trial one to trial two for several voluntary measures of RTD, while there was only one for the evoked measures of RTD. CONCLUSIONS: There is dissociation in the reliability of voluntary and evoked PT, and RTD, such that the evoked measurements display greater reliability in older men. Voluntary RTDs were most suspect, consistently demonstrating lower ICCs and greater SEMs than evoked RTD. However, if choosing to measure voluntary RTD in older men, the most reliable measurements may be RTD in the first 10 ms, 80-110 ms, or overall RTD. Finally, EMD may be unreliable in older men. Adviser: Joel T. Crame

Novel Energy Drink Improves Mood and Raises Blood Pressure, but has No Effect on Cardiac QTc Interval or Rate-Pressure Product in Young Adult Gamers

Novel energy drink formulations have been introduced to the market that are purported to have nootropic effects – including improving mood. Despite their rapidly growing popularity, especially among video gamers, there is minimal evidence supporting their efficacy or establishing their cardiovascular safety profiles. PURPOSE: We conducted a randomized, double-blind, placebo-controlled, crossover trial to investigate the effects of acute consumption of a non-caloric, novel energy drink (NED) containing 200 mg caffeine, citicoline, tyrosine, B-vitamins, and carboxylic acids on mood and cardiovascular safety outcomes. We hypothesized that NED would improve mood without significant adverse cardiovascular effects when compared to placebo. METHODS: Forty-five healthy young adults who routinely play video games (37M, 8F; mean ± SD, age = 25 ± 6 y) each completed two experimental study visits in randomized order where they consumed either NED or a placebo matched for volume, calories, taste, appearance, and mouthfeel. Resting systolic and diastolic blood pressure (SBP and DBP) and an electrocardiogram (ECG) were obtained from each participant after a 10-min quiescent period prior to and 45 minutes after consumption of NED or placebo. Resting heart rate (RHR) and corrected QT interval length (QTc) were derived from the ECG. Rate-pressure product (RPP) was determined as the product of HR and SBP. Mood was assessed using the Profile of Mood States at post-consumption after BP and ECG assessments. Paired t-tests or signed ranked tests (for non- normally distributed data) were used to examine between-condition differences in mood states, whereas 2 (condition) × 2 (time) ANOVAs were used to examine SBP, DBP, QTc, and RPP. RESULTS: Change scores are presented as mean absolute change ± 95% confidence interval. Relative changes are provided for mood data. Acute NED consumption improved fatigue-inertia (-1.4 ± 1.0 a.u. [+36%]; p = 0.004), vigor-activity (+2.4 ± 1.2 a.u. [+33%]; p \u3c 0.001), and friendliness (+0.7 ± 0.7 a.u. [+7%]; p = 0.04), without adverse effects on tension-anxiety, confusion-bewilderment, or depression-dejection (all p ≥ 0.27). RHR decreased from pre- to post-beverage consumption, and this decrease was greater following NED than placebo consumption (-6.0 ± 2.8 vs. -2.6 ± 1.4 bpm, p = 0.017). SBP (+3.7 ± 2.0 vs. -0.4 ± 2.0 mmHg; p = 0.002) and DBP (+3.7 ± 1.7 vs. -0.04 ± 1.4 mmHg; p = 0.003) increased following NED vs. placebo; however, RPP decreased independent of condition (-386.0 ± 229.0; p = 0.03), and there was no effect of beverage consumption on QTc (p = 0.44). CONCLUSION: Acute NED consumption improved mood states related to vigor, fatigue, and friendliness without affecting tension-anxiety, depression, or confusion in young adult gamers. While NED consumption produced mild increases in SBP and DBP, there were no effects on either QTc or RPP. Thus, overall, NED consumption produces mood-enhancing effects without markedly influencing cardiovascular safety outcomes

Physiological Responses Underlying the Perception of Effort during Moderate and Heavy Intensity Cycle Ergometry

This study examined patterns of responses for physiological and perceptual variables during cycle ergometry at a constant rate of perceived exertion (RPE) within the moderate and heavy exercise intensity domains. Nineteen (mean age 21.3 ± 0.5 years; 43.4 ± 2.0 mL·kg−1·min−1 VO2Peak) moderately trained cyclists performed an incremental test to exhaustion and two 60 min constant RPE rides at the RPE corresponding to the gas exchange threshold (RPEGET) and 15% above the GET (RPEGET+15%). Oxygen consumption (VO2), respiratory exchange ratio (RER), heart rate (HR), minute ventilation (VE), breathing frequency (FB), and power output (PO) were monitored throughout the rides. Polynomial regression analyses showed VO2, RER, HR, and VE (correlation = −0.85 to −0.98) tracked the decreases in PO required to maintain a constant RPE. Only FB tracked RPE during the moderate and heavy intensity rides. Repeated measures ANOVAs indicated that VO2 during the 60 min rides at RPEGET was not different (p \u3e 0.05) from VO2 at GET from the incremental test to exhaustion. Thus, monitoring intensity using an RPE associated with the GET is sustainable for up to 60 min of cycling exercise and a common mechanism may mediate FB and the perception of effort during moderate and heavy intensity cycle ergometry

Physiological Responses Underlying the Perception of Effort during Moderate and Heavy Intensity Cycle Ergometry

This study examined patterns of responses for physiological and perceptual variables during cycle ergometry at a constant rate of perceived exertion (RPE) within the moderate and heavy exercise intensity domains. Nineteen (mean age 21.3 ± 0.5 years; 43.4 ± 2.0 mL·kg−1·min−1 VO2Peak) moderately trained cyclists performed an incremental test to exhaustion and two 60 min constant RPE rides at the RPE corresponding to the gas exchange threshold (RPEGET) and 15% above the GET (RPEGET+15%). Oxygen consumption (VO2), respiratory exchange ratio (RER), heart rate (HR), minute ventilation (VE), breathing frequency (FB), and power output (PO) were monitored throughout the rides. Polynomial regression analyses showed VO2, RER, HR, and VE (correlation = −0.85 to −0.98) tracked the decreases in PO required to maintain a constant RPE. Only FB tracked RPE during the moderate and heavy intensity rides. Repeated measures ANOVAs indicated that VO2 during the 60 min rides at RPEGET was not different (p \u3e 0.05) from VO2 at GET from the incremental test to exhaustion. Thus, monitoring intensity using an RPE associated with the GET is sustainable for up to 60 min of cycling exercise and a common mechanism may mediate FB and the perception of effort during moderate and heavy intensity cycle ergometry

Individual Responses for Muscle Activation, Repetitions, and Volume during Three Sets to Failure of High- (80% 1RM) \u3ci\u3eversus\u3c/i\u3e Low-Load (30% 1RM) Forearm Flexion Resistance Exercise

This study compared electromyographic (EMG) amplitude, the number of repetitions completed, and exercise volume during three sets to failure of high- (80% 1RM) versus low-load (30% 1RM) forearm flexion resistance exercise on a subject-by-subject basis. Fifteen men were familiarized, completed forearm flexion 1RM testing. Forty-eight to 72 h later, the subjects completed three sets to failure of dumbbell forearm flexion resistance exercise with 80% (n = 8) or 30% (n = 7) 1RM. EMG amplitude was calculated for every repetition, and the number of repetitions performed and exercise volume were recorded. During sets 1, 2, and 3, one of eight subjects in the 80% 1RM group demonstrated a significant linear relationship for EMG amplitude versus repetition. For the 30% 1RM group, seven, five, and four of seven subjects demonstrated significant linear relationships during sets 1, 2, and 3, respectively. The mean EMG amplitude responses show that the fatigue-induced increases in EMG amplitude for the 30% 1RM group and no change in EMG amplitude for the 80% 1RM group resulted in similar levels of muscle activation in both groups. The numbers of repetitions completed were comparatively greater, while exercise volumes were similar in the 30% versus 80% 1RM group. Our results, in conjunction with those of previous studies in the leg extensors, suggest that there may be muscle specific differences in the responses to high- versus low-load exercise

International society of sports nutrition position stand: caffeine and exercise performance

Following critical evaluation of the available literature to date, The International Society of Sports Nutrition (ISSN) position regarding caffeine intake is as follows: 1. Supplementation with caffeine has been shown to acutely enhance various aspects of exercise performance in many but not all studies. Small to moderate benefits of caffeine use include, but are not limited to: muscular endurance, movement velocity and muscular strength, sprinting, jumping, and throwing performance, as well as a wide range of aerobic and anaerobic sport-specific actions. 2. Aerobic endurance appears to be the form of exercise with the most consistent moderate-to-large benefits from caffeine use, although the magnitude of its effects differs between individuals. 3. Caffeine has consistently been shown to improve exercise performance when consumed in doses of 3–6 mg/ kg body mass. Minimal effective doses of caffeine currently remain unclear but they may be as low as 2 mg/kg body mass. Very high doses of caffeine (e.g. 9 mg/kg) are associated with a high incidence of side-effects and do not seem to be required to elicit an ergogenic effect. 4. The most commonly used timing of caffeine supplementation is 60 min pre-exercise. Optimal timing of caffeine ingestion likely depends on the source of caffeine. For example, as compared to caffeine capsules, caffeine chewing gums may require a shorter waiting time from consumption to the start of the exercise session. 5. Caffeine appears to improve physical performance in both trained and untrained individuals. 6. Inter-individual differences in sport and exercise performance as well as adverse effects on sleep or feelings of anxiety following caffeine ingestion may be attributed to genetic variation associated with caffeine metabolism, and physical and psychological response. Other factors such as habitual caffeine intake also may play a role in between-individual response variation. 7. Caffeine has been shown to be ergogenic for cognitive function, including attention and vigilance, in most individuals. 8. Caffeine may improve cognitive and physical performance in some individuals under conditions of sleep deprivation. 9. The use of caffeine in conjunction with endurance exercise in the heat and at altitude is well supported when dosages range from 3 to 6 mg/kg and 4–6 mg/kg, respectively. 10. Alternative sources of caffeine such as caffeinated chewing gum, mouth rinses, energy gels and chews have been shown to improve performance, primarily in aerobic exercise. 11. Energy drinks and pre-workout supplements containing caffeine have been demonstrated to enhance both anaerobic and aerobic performance

Reliability and Minimum Detectable Change for Common Clinical Physical Function Tests in Sarcopenic Men and Women

Objectives: To determine the test–retest reliability and minimum detectable change scores for seven common clinical measurements of muscle strength and physical function in a multiethnic sample of sarcopenic, malnourished men and women. Design: Each participant visited the laboratory seven times over 25 to 26 weeks. Reliability was assessed for each measurement from Familiarization 1 to Familiarization 2 (R1), Familiarization 2 to baseline testing (R2), Familiarization 3 to 12-week testing (R3), and Familiarization 4 to 24-week testing (R4). Setting: Data were collected during a clinical trial at 23 sites in the United States, Belgium, Italy, Mexico, Poland, Spain, Switzerland, and the United Kingdom. Participants: Sarcopenic, malnourished, older adults (N = 257; n = 98 men aged 76.8 ± 6.3, n = 159 women aged 75.9 ± 6.6). Measurements: During each visit, participants completed the Short Physical Performance Battery (SPBB) and isometric handgrip and isokinetic leg extensor and flexor strength testing at a slow (1.05 rad/s) and fast (3.15 rad/s) velocity. Results: Handgrip strength, gait speed, SPPB score, and isokinetic leg extension and flexion peak torque (PT) had intraclass correlation coefficients (ICCs) that were significantly greater than 0 (all ≥ 0.59) at R1, R2, R3, and R4, although most of these variables demonstrated systematic increases at R1, and several exhibited systematic variability beyond the baseline testing session. Conclusion: The ICCs and standard errors of the measurement (SEMs) generally improved with familiarization, which emphasizes the need for at least one familiarization trial for these measurements in sarcopenic, malnourished older adults. A three tier-approach to interpreting the clinical importance of statistically significant results that includes null hypothesis testing, examination and interpretation of the effect magnitude, and comparison of individual changes with the SEM and minimum detectable change of the measurements used is recommended. Includes supplementary materials

Neuromuscular adaptations to three and six weeks of high-versus low-load resistance training

The purpose of this study was to examine the neuromuscular adaptations following 3 and 6 weeks of 80% versus 30% one repetition maximum (1RM) resistance training to failure in the leg extensors. 26 men (mean ± SD; age = 23.1 ± 4.7 yrs) were randomly assigned to a high- (80% of 1RM; n = 13) or low-load (30% of 1RM; n = 13) resistance training group and completed leg extension resistance training to failure 3 times per week for 6 weeks. Testing was completed at baseline, 3, and 6 weeks of training. During each testing session, ultrasound muscle thickness (MT) and echo intensity (EI), 1RM strength, and maximal voluntary isometric contraction (MVIC) strength were measured. Percent voluntary activation (VA) and electromyographic (EMG) and mechanomyographic (MMG) amplitude (AMP) and mean power frequency (MPF) were measured during MVIC, and during randomly ordered isometric step muscle actions at 10 - 100% of the baseline MVIC. The results indicated that MT increased (2.8 – 3.0% and 6.0 – 6.6%) and EI (-3.8% and -6.8%) decreased similarly from Baseline to Week 3 and Baseline to Week 6, respectively, in the 80% and 30% 1RM groups. However, in the 80% 1RM group, 1RM strength increased by 14.7% and 27.7% and MVIC strength increased 11.8% and 28.0% from Baseline to Week 3 and Week 6, respectively. In the 30% 1RM group, 1RM strength decreased by 3.5% and increased by 9.5% and MVIC strength decreased by 4.3% and increased by 13.4% from Baseline to Week 3 and Week 6, respectively. There were similar changes in VA, EMG AMP, and MMG AMP in the 80% and 30% 1RM groups during MVIC. However, there were greater neuromuscular adaptations at submaximal torques in the 80% versus 30% 1RM group, which were evident in the VA, EMG, and MMG responses. Therefore, despite causing similar muscle hypertrophy, 80% 1RM enhanced muscle strength to a greater degree than 30% 1RM and resulted in an increased efficiency of activation that was especially apparent at high contraction intensities (i.e., ∼ 60 – 100% MVIC). These results suggest differences in the neuromuscular adaptations to high- versus low-load resistance training that may explain the disparate increases in muscle strength despite similar muscle hypertrophy in response to these two training modes

Influence of stretching velocity on musculotendinous stiffness of the hamstrings during passive straight-leg raise assessments

Background Recently, passive musculotendinous stiffness (MTS) has been assessed manually in the field; however, when conducting these types of assessments, the stretching velocity must be controlled to avoid eliciting the stretch reflex, which can be observed by increased electromyographic (EMG) amplitude of the stretched muscles and greater resistive torque (indicating the assessment is no longer passive). Objective To examine the effects of slow, medium, and fast stretching velocities during manually-applied passive straight-leg raise (SLR) assessments on hamstrings MTS and EMG amplitude characteristics. Study design Crossover study. Methods Twenty-three healthy, young adults underwent passive, manually-applied SLR assessments performed by the primary investigator at slow, medium, and fast stretching velocities. During each SLR, MTS and EMG amplitude were determined at 4 common joint angles (θ) separated by 5° during the final common 15° of range of motion for each participant. Results The average stretching velocities were 7, 11, and 18°·s−1 for the slow, medium, and fast SLRs. There were no velocity-related differences for MTS (P = 0.489) or EMG amplitude (P = 0.924). MTS increased (P \u3c 0.001) with joint angle (θ1\u3cθ2\u3cθ3\u3cθ4); however, EMG amplitude remained unchanged (P = 0.885) across the range of motion. Conclusions Although velocity discrepancies have been identified as a potential threat to the validity of passive MTS measurements obtained with manual SLR techniques, the present findings suggest that the SLR at any of the velocities tested in our study (7–18°·s−1) did not elicit a detectible stretch reflex, and thereby may be appropriate for examining MTS