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1.
J Strength Cond Res ; 35(11): 3265-3269, 2021 Nov 01.
Article in English | MEDLINE | ID: mdl-31453941

ABSTRACT

ABSTRACT: Jenkins, NDM, Miramonti, AA, Hill, EC, Smith, CM, Cochrane-Snyman, KC, Housh, TJ, and Cramer, JT. Mechanomyographic amplitude is sensitive to load-dependent neuromuscular adaptations in response to resistance training. J Strength Cond Res 35(11): 3265-3269, 2021-We examined the sensitivity of the mechanomyographic amplitude (MMGRMS) and frequency (MMGMPF) vs. torque relationships to load-dependent neuromuscular adaptations in response to 6 weeks of higher- vs. lower-load resistance training. Twenty-five men (age = 22.8 ± 4.6 years) were randomly assigned to either a high- (n = 13) or low-load (n = 12) training group and completed 6 weeks of leg extension resistance training at 80 or 30% 1RM. Before and after 3 and 6 weeks of training, mechanomyography signals were recorded during isometric contractions at target torques equal to 10-100% of the subjects' baseline maximal strength to quantify MMGRMS and MMGMPF vs. torque relationships. MMGRMS decreased from Baseline to weeks 3 and 6 in the high-load, but not low-load group, and was dependent on the muscle and intensity of contraction examined. Consequently, MMGRMS was generally lower in the high- than low-load group at weeks 3 and 6, and these differences were most apparent in the vastus lateralis (VL) and rectus femoris muscles at higher contraction intensities. MMGMPF was greater in the high- than low-load training group independent of time or muscle. The MMGRMS vs. torque relationship was sensitive to load-dependent, muscle-specific neuromuscular adaptations and suggest reductions in neuromuscular activation to produce the same absolute submaximal torques after training with high, but not low loads.


Subject(s)
Resistance Training , Adaptation, Physiological , Adolescent , Adult , Electromyography , Humans , Isometric Contraction/physiology , Male , Muscle Strength/physiology , Muscle, Skeletal/physiology , Quadriceps Muscle/physiology , Torque , Young Adult
2.
J Strength Cond Res ; 34(10): 2849-2856, 2020 Oct.
Article in English | MEDLINE | ID: mdl-29489728

ABSTRACT

McKay, BD, Miramonti, AA, Gillen, ZM, Leutzinger, TJ, Mendez, AI, Jenkins, NDM, and Cramer, JT. Normative reference values for high school-aged American football players. J Strength Cond Res 34(10): 2849-2856, 2020-The purpose of the present report was to provide test- and position-specific normative reference values for combine test results based on a large, nationally representative sample of high school-aged American football players in their freshman, sophomore, and junior classes. Cross-sectional anthropometric and performance data were obtained from 12 different high school American football recruiting combines between March 7, 2015, and January 9, 2016, across the United States. Subjects included a sample (n = 7,478) of high school-aged American football athletes in their junior (n = 3,779), sophomore (n = 2,514), and freshman (n = 1,185) classes. The database included combine date, school state, position, class, height, body mass (BM), 40-yard dash, pro-agility, 3-cone, vertical jump, broad jump, and power push-up. Each player self-classified their American football positions as defensive back, defensive end, defensive linemen, linebacker, offensive linemen, quarterback, running back, tight end (TE), or wide receiver. Test- and position-specific normative values were generated by aggregating data from freshman, sophomore, and junior classes. Mean differences were found among classes for all positions and all measurements (p ≤ 0.05), except for TE BM (p > 0.05). Greater differences for all variables were observed from freshman to sophomore classes than from sophomore to junior classes. These normative reference values may provide realistic comparisons and evaluations in performance for young American football players, parents, and coaches with collegiate football aspirations. High school strength and conditioning professionals should use these norms to set attainable goals and reward accomplishments for young football players.


Subject(s)
Athletes , Athletic Performance/physiology , Athletic Performance/standards , Football/physiology , Football/standards , Adolescent , Adult , Anthropometry , Body Height , Body Mass Index , Cross-Sectional Studies , Exercise Test , Humans , Male , Reference Values , Running/physiology , Running/standards , United States , Universities
3.
J Strength Cond Res ; 34(4): 1184-1187, 2020 Apr.
Article in English | MEDLINE | ID: mdl-30418328

ABSTRACT

McKay, BD, Miramonti, AA, Gillen, ZM, Leutzinger, TJ, Mendez, AI, Jenkins, NDM, and Cramer, JT. Normative reference values for high school-aged American football players: Proagility drill and 40-yard dash split times. J Strength Cond Res 34(4): 1184-1187, 2020-The purpose of this short report was to provide test- and position-specific normative reference values for the 10- and 20-yd split times (10YD and 20YD) during the 40-yd dash (40YD) as well as 10-yd split times during the proagility drill (PA) based on a large, nationally representative sample of high school-aged American football players in their freshman, sophomore, and junior classes. Cross-sectional performance data were obtained from 12 different high school American football recruiting combines between March 7, 2015, and January 9, 2016, across the United States. The sample included (n = 7,478) high school-aged American football athletes in their freshman (n = 1,185), sophomore (n = 2,514), and junior (n = 3,779) classes. Each player self-classified their American football positions as defensive back, defensive end, defensive linemen, linebacker, offensive linemen (OL), quarterback (QB), running back, tight end, or wide receiver. The results of the freshman, sophomore, and junior class were aggregated to generate test- and position-specific normative values. Mean differences were found among classes for all positions and all measurements (p ≤ 0.05) except for OL and QB PA split time (p > 0.05). Greater percent differences for all 3 variables were observed between freshman and sophomore years than between sophomore and junior years. These normative reference values will be useful for athletes, parents, coaches, and high school strength and conditioning professionals to set realistic goals for young American football athletes.


Subject(s)
Athletic Performance/physiology , Football/physiology , Running/physiology , Adolescent , Athletes , Body Weights and Measures , Cross-Sectional Studies , Humans , Male , Reference Values , United States
4.
J Strength Cond Res ; 32(11): 3119-3126, 2018 Nov.
Article in English | MEDLINE | ID: mdl-30540280

ABSTRACT

Mendez, AI, Miramonti, AA, Gillen, ZM, McKay, BD, Leutzinger, TJ, and Cramer, JT. Stature, body mass, and BMI in high school american football players: Appropriate determinants of obesity prevalence? J Strength Cond Res 32(11): 3119-3126, 2018-The purpose of this study was to evaluate stature (HT), mass (BM), body mass index (BMI), and obesity prevalence based on BMI categories in a large sample (n = 7,175) of high school American football players enrolled as freshmen, sophomores, or juniors. Players were categorized by their positions: offensive linemen (OLs), defensive linemen (DLs), tight end, defensive end, linebacker, running back, quarterback, defensive back, and wide receiver. The HT, BM, and BMI increased as grade increased among all positions. Offensive lineman and DL had the greatest HT, BM, and BMI (p ≤ 0.05). Obesity prevalence was greatest in OL and DL. When accounting for age-related increases in BMI, BM increased to a greater degree than HT. If HT is an indirect indicator of skeletal size, although BM is more influenced by soft tissue, then the age-related BMI increases in this study may be largely accounted for by soft-tissue changes rather than skeletal growth. Although obesity prevalence in OL (94.5%) and DL (78.4%) positions was greater than all other positions as determined from BMI, it is impossible to know the allocations of fat-free and fat mass-particularly in American football athletes. If obesity continues to be defined as an unhealthy accumulation of fat, then athletes who may have a greater relative proportion of lean soft tissue should not be classified as obese using BMI (BM ÷ HT). More sophisticated, reliable, and sensitive measure of body composition, such as skinfolds, may be more appropriate field measurements.


Subject(s)
Body Height , Body Mass Index , Football , Obesity/epidemiology , Adolescent , Athletes , Body Composition , Humans , Male , Prevalence , Schools , United States
5.
Int J Exerc Sci ; 11(4): 198-213, 2018.
Article in English | MEDLINE | ID: mdl-29795731

ABSTRACT

The influence of baseline strength or muscle size on adaptations to training is not well-understood. Comparisons between novice and advanced lifters, and between stronger and weaker experienced-lifters, have produced conflicting results. This study examined the effect of baseline muscle strength and size on subsequent adaptations in resistance-trained individuals following a traditional high-volume, short-rest resistance training protocol. Fourteen resistance-trained men (24.0±2.7 y; 90.1±11.7 kg; 169.9±29.0 cm) completed pre-training (PRE) ultrasound measurements of muscle cross-sectional area (CSA) in the rectus femoris (RF), vastus lateralis (VL), pectoralis major, and triceps brachii (TRI) prior to strength assessments (e.g., one-repetition maximum strength bench press and back-squat). Post-training (POST) assessments were completed following 8-wks (4 d·wk-1) of resistance training. Comparisons were made between stronger (STR) and weaker (WKR) participants, and between larger (LGR) and smaller (SMR) participants, based upon PRE-muscle strength and size, respectively. When groups were based on upper-body strength, repeated measures analysis of variance indicated a significant group × time interaction where greater improvements in bench press strength were observed in WKR (12.5±8.6%, p = 0.013) compared to STR (1.3±5.4%, p=0.546). Within this comparison, STR also possessed more resistance training experience than WKR (mean difference=3.1 y, p=0.002). No other differences in experience or adaptations to training were observed. These data suggest that following a short-duration training program (8-weeks), baseline size and strength have little impact on performance gains in resistance-trained individuals who possess similar years of experience. However, when training experience is different, baseline strength may affect adaptations.

6.
J Strength Cond Res ; 32(10): 2783-2794, 2018 Oct.
Article in English | MEDLINE | ID: mdl-29465606

ABSTRACT

Gillen, ZM, Miramonti, AA, McKay, BD, Leutzinger, TJ, and Cramer, JT. Test-retest reliability and concurrent validity of athletic performance combine tests in 6-15-year-old male athletes. J Strength Cond Res 32(10): 2783-2794, 2018-Athletic performance combine tests are used by high school, collegiate, and professional American football programs to evaluate performance; however, limited evidence is available on performance combine test results in youth athletes. The purposes of this study were to report test-retest reliability statistics and evaluate concurrent validity among combine performance tests in 6-15-year-old male athletes. Sixty-nine young male athletes (mean ± SD; age = 10.9 ± 2.1 years, height = 154.4 ± 13.6 cm, body mass = 46.8 ± 16.0 kg) were divided into 3 age groups: 6-9 years (n = 16), 10-11 years (n = 26), and 12-15 years (n = 27). Participants completed 2 attempts of the vertical jump (VJ), broad jump (BJ), pro-agility (PA), L-cone (LC) drill, and 10-, 20-, 40-yd dashes. The results indicated that the older age groups performed better on most performance assessments compared with the 6-9-year group (p ≤ 0.05). The combine tests demonstrated consistently adequate reliability for all age groups, except for the 10-yd dash, which was deemed unreliable. Evidence of concurrent validity, and possible measurement redundancy were observed in the VJ vs. BJ, PA vs. LC, and 20 vs. 40 yd, but zero- and first-order partial correlations suggested that only the PA and LC were redundant, and the PA may be superior for this age group over the LC. Although the VJ and BJ provide independent performance information regarding lower-body power, questions regarding the redundancy of the 20 vs. 40 yd remain unanswered from a measurement perspective.


Subject(s)
Athletic Performance/physiology , Exercise Test/standards , Reproducibility of Results , Adolescent , Athletes , Child , Cross-Sectional Studies , Humans , Male
7.
J Strength Cond Res ; 32(1): 83-96, 2018 Jan.
Article in English | MEDLINE | ID: mdl-29084096

ABSTRACT

Gillen, ZM, Miramonti, AA, McKay, BD, Jenkins, NDM, Leutzinger, TJ, and Cramer, JT. Reliability and sensitivity of the power push-up test for upper-body strength and power in 6-15-year-old male athletes. J Strength Cond Res 32(1): 83-96, 2018-The power push-up (PPU) test is an explosive upper-body test performed on a force plate and is currently being used in high school football combines throughout the United States. The purpose of this study was to quantify the reliability of the PPU test based on age and starting position (knees vs. toes) in young athletes. Sixty-eight boys (mean ± SD; age = 10.8 ± 2.0 years) were tested twice over 5 days. Boys were separated by age as 6-9 years (n = 16), 10-11 years (n = 26), and 12-15 years (n = 26). The PPU test was performed on a force plate while rotating from the knees vs. the toes. Measurements were peak force (PF, N), peak rate of force development (pRFD, N·s), average power (AP, W), and peak power (PP, W). Intraclass correlation coefficients (ICC2,1), SEMs, coefficients of variation (CVs), and minimum detectable changes (MDCs) were calculated to quantify reliability and sensitivity. Peak force from the knees in 10-15-year-olds, PF from the toes in 12-15-year-olds, and pRFD from the knees and toes in 12-15-year-olds were comparably reliable (ICC ≥ 0.84). Neither power measurements (AP or PP) for any age group, nor any measurements (PF, pRFD, AP, or PP) for the 6-9-year-olds were comparably reliable (ICC ≤ 0.74). When considering the reliable variables, PF was greater in the 12-15-year-olds than in 10-11-year-olds (p ≤ 0.05). In addition, in 12-15-year-olds, PF and pRFD were greater from the knees than from the toes (p ≤ 0.05). For reasons largely attributable to growth and development, the PPU test may be a reliable (ICC ≥ 0.80) and sensitive (CV ≤ 19%) measure of upper-body strength (PF), whereas pRFD was also reliable (ICC ≥ 0.80), but less sensitive (CV = 30-38%) in 10-15-year-old male athletes.


Subject(s)
Athletes , Exercise Test/methods , Muscle Strength/physiology , Muscle, Skeletal/physiology , Adolescent , Child , Exercise Test/standards , Humans , Male , Reproducibility of Results
8.
Front Physiol ; 8: 331, 2017.
Article in English | MEDLINE | ID: mdl-28611677

ABSTRACT

We examined the neuromuscular adaptations following 3 and 6 weeks of 80 vs. 30% one repetition maximum (1RM) resistance training to failure in the leg extensors. Twenty-six men (age = 23.1 ± 4.7 years) were randomly assigned to a high- (80% 1RM; n = 13) or low-load (30% 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 and echo intensity, 1RM strength, maximal voluntary isometric contraction (MVIC) strength, and contractile properties of the quadriceps femoris were measured. Percent voluntary activation (VA) and electromyographic (EMG) amplitude were measured during MVIC, and during randomly ordered isometric step muscle actions at 10-100% of baseline MVIC. There were similar increases in muscle thickness from Baseline to Week 3 and 6 in the 80 and 30% 1RM groups. However, both 1RM and MVIC strength increased from Baseline to Week 3 and 6 to a greater degree in the 80% than 30% 1RM group. VA during MVIC was also greater in the 80 vs. 30% 1RM group at Week 6, and only training at 80% 1RM elicited a significant increase in EMG amplitude during MVIC. The peak twitch torque to MVIC ratio was also significantly reduced in the 80%, but not 30% 1RM group, at Week 3 and 6. Finally, VA and EMG amplitude were reduced during submaximal torque production as a result of training at 80% 1RM, but not 30% 1RM. Despite eliciting similar hypertrophy, 80% 1RM improved muscle strength more than 30% 1RM, and was accompanied by increases in VA and EMG amplitude during maximal force production. Furthermore, training at 80% 1RM resulted in a decreased neural cost to produce the same relative submaximal torques after training, whereas training at 30% 1RM did not. Therefore, our data suggest that high-load training results in greater neural adaptations that may explain the disparate increases in muscle strength despite similar hypertrophy following high- and low-load training programs.

9.
J Strength Cond Res ; 31(5): 1403-1410, 2017 May.
Article in English | MEDLINE | ID: mdl-28146033

ABSTRACT

McKay, BD, Yeo, NM, Jenkins, NDM, Miramonti, AA, and Cramer, JT. Exertional rhabdomyolysis in a 21-year-old healthy woman: a case report. J Strength Cond Res 31(5): 1403-1410, 2017-The optimal resistance training program to elicit muscle hypertrophy has been recently debated and researched. Although 3 sets of 10 repetitions at 70-80% of the 1 repetition maximum (1RM) are widely recommended, recent studies have shown that low-load (∼30% 1RM) high-repetition (3 sets of 30-40 repetitions) resistance training can elicit similar muscular hypertrophy. Incidentally, this type of resistance training has gained popularity. In the process of testing this hypothesis in a research study in our laboratory, a subject was diagnosed with exertional rhabdomyolysis after completing a resistance training session that involved 3 sets to failure at 30% 1RM. Reviewed were the events leading up to and throughout the diagnosis of exertional rhabdomyolysis in a healthy recreationally-trained 21-year-old woman who was enrolled in a study that compared the acute effects of high-load low-repetition vs. low-load high-repetition resistance training. The subject completed a total of 143 repetitions of the bilateral dumbbell biceps curl exercise. Three days after exercise, she reported excessive muscle soreness and swelling and sought medical attention. She was briefly hospitalized and then discharged with instructions to take acetaminophen for soreness, drink plenty of water, rest, and monitor her creatine kinase (CK) concentrations. Changes in the subject's CK concentrations, ultrasound-determined muscle thickness, and echo intensity monitored over a 14-day period are reported. This case illustrates the potential risk of developing exertional rhabdomyolysis after a low-load high-repetition resistance training session in healthy, young, recreationally-trained women. The fact that exertional rhabdomyolysis is a possible outcome may warrant caution when prescribing this type of resistance exercise.


Subject(s)
Muscle, Skeletal/physiopathology , Resistance Training/adverse effects , Resistance Training/methods , Rhabdomyolysis/etiology , Creatine Kinase/blood , Female , Humans , Rest , Rhabdomyolysis/diagnosis , Young Adult
10.
Muscle Nerve ; 55(3): 344-349, 2017 03.
Article in English | MEDLINE | ID: mdl-27422091

ABSTRACT

INTRODUCTION: The purpose of this study was to determine the validity of the maximal distance-electromyography (Dmax-EMG) method for estimating physical working capacity at fatigue threshold (PWCFT ). METHODS: Twenty-one men and women (age 22.9 ± 3.0 years) volunteered to perform 12 sessions of high-intensity interval training (HIIT) over 4 weeks. Before and after HIIT training, a graded exercise test (GXT) was used to estimate PWCFT using the Dmax method and the original (ORG) method. RESULTS: There was a significant increase in PWCFT for both ORG (+10.6%) and Dmax (+12.1%) methods, but no significant difference in the change values between methods. Further, Bland-Altman analyses resulted in non-significant biases (ORG-Dmax) between methods at pre-HIIT (-6.4 ± 32.5 W; P > 0.05) and post-HIIT (-4.2 ± 33.1 W; P > 0.05). CONCLUSION: The Dmax method is sensitive to training and is a valid method for estimating PWCFT in young men and women. Muscle Nerve 55: 344-349, 2017.


Subject(s)
Exercise/physiology , Muscle Fatigue/physiology , Physical Education and Training , Work Capacity Evaluation , Adult , Analysis of Variance , Electromyography , Exercise Test , Female , Healthy Volunteers , Humans , Male , Physical Examination , Young Adult
11.
Muscle Nerve ; 56(1): 107-116, 2017 07.
Article in English | MEDLINE | ID: mdl-27718510

ABSTRACT

INTRODUCTION: In this study we examined relationships among mechanomyographic (MMG), electromyographic (EMG), and peak twitch torque (PTT) responses as well as test-retest reliability when recorded during recruitment curves in the soleus muscle. METHODS: PTT, EMG (M-wave, H-reflex), and MMG responses were recorded during recruitment curves in 16 subjects (age 24 ± 2 years) on 2 separate days. The sum of the M-wave and H-reflex (M+H) was calculated. Correlations among variables and test-retest reliability were determined. RESULTS: MMG was correlated with PTT (mean r = 0.93, range r = 0.59-0.99), the M-wave (0.95, 0.04-0.98), and M+H (0.91, 0.42-0.97), but was unrelated to the H-reflex (-0.06, -0.56 to 0.47). Reliability was consistently high among most variables, but normalizing to the maximum value improved MMG reliability and the minimum detectable change. CONCLUSION: MMG responses predicted 86%-90% of the variability in PTT, M-wave, and M+H; thus, MMG may be a useful alternative for estimating twitch torque and maximal activation. Muscle Nerve 56: 107-116, 2017.


Subject(s)
H-Reflex/physiology , Muscle Contraction/physiology , Muscle, Skeletal/physiology , Torque , Action Potentials/physiology , Adult , Analysis of Variance , Electromyography , Female , Humans , Male , Physical Stimulation , Psychophysics , Young Adult
12.
J Strength Cond Res ; 31(1): 45-53, 2017 Jan.
Article in English | MEDLINE | ID: mdl-28005636

ABSTRACT

Mangine, GT, Hoffman, JR, Gonzalez, AM, Townsend, JR, Wells, AJ, Jajtner, AR, Beyer, KS, Boone, CH, Wang, R, Miramonti, AA, LaMonica, MB, Fukuda, DH, Witta, EL, Ratamess, NA, and Stout, JR. Exercise-induced hormone elevations are related to muscle growth. J Strength Cond Res 31(1): 45-53, 2017-Partial least squares regression structural equation modeling (PLS-SEM) was used to examine relationships between the endocrine response to resistance exercise and muscle hypertrophy in resistance-trained men. Pretesting (PRE) measures of muscle size (thickness and cross-sectional area) of the vastus lateralis and rectus femoris were collected in 26 resistance-trained men. Participants were randomly selected to complete a high-volume (VOL, n = 13, 10-12RM, 1-minute rest) or high-intensity (INT, n = 13, 3-5RM, 3-minute rest) resistance training program. Blood samples were collected at baseline, immediately postexercise, 30-minute, and 60-minute postexercise during weeks 1 (week 1) and 8 (week 8) of training. The hormonal responses (testosterone, growth hormone [22 kD], insulin-like growth factor-1, cortisol, and insulin) to each training session were evaluated using area-under-the-curve (AUC) analyses. Relationships between muscle size (PRE), AUC values (week 1 + week 8) for each hormone, and muscle size (POST) were assessed using a consistent PLS-SEM algorithm and tested for statistical significance (p ≤ 0.05) using a 1,000 samples consistent bootstrapping analysis. Group-wise comparisons for each relationship were assessed through independent t-tests. The model explained 73.4% (p < 0.001) of variance in muscle size at POST. Significant pathways between testosterone and muscle size at PRE (p = 0.043) and muscle size at POST (p = 0.032) were observed. The ability to explain muscle size at POST improved when the model was analyzed by group (INT: R = 0.882; VOL: R = 0.987; p < 0.001). No group differences in modal quality were found. Exercise-induced testosterone elevations, independent of the training programs used in this study, seem to be related to muscle growth.


Subject(s)
Muscle, Skeletal/physiology , Resistance Training/methods , Adult , Athletes , Human Growth Hormone/blood , Humans , Hydrocortisone/blood , Insulin-Like Growth Factor I/biosynthesis , Male , Muscle, Skeletal/blood supply , Quadriceps Muscle/physiology , Rest/physiology , Testosterone/blood , Young Adult
13.
Physiol Meas ; 37(11): 1993-2002, 2016 11.
Article in English | MEDLINE | ID: mdl-27754975

ABSTRACT

The purposes of the present study were to apply a unique method for the identification of the time course of changes in neuromuscular responses and to infer the motor unit activation strategies used to maintain force during a fatiguing, intermittent isometric workbout. Eleven men performed 50, 6 s intermittent isometric muscle actions of the leg extensors, each separated by 2 s of rest at 60% maximal voluntary isometric contraction (MVIC). Electromyographic (EMG) and mechanomyographic (MMG) amplitude (root mean square; RMS) and frequency (mean power frequency; MPF) were obtained from the vastus lateralis (VL) every 5 of the 50 repetitions and normalized as a percent of the initial repetition. Polynomial regression analyses were used to determine the model of best fit for the normalized EMG RMS, EMG MPF, MMG RMS, and MMG MPF versus repetition relationships and one-way repeated measures ANOVAs with post-hoc Student Newman-Keuls were used to identify when these neuromuscular parameters changed from the initial repetition. The findings of the present study indicated two unique phases of neuromuscular responses (repetitions 1-20 and 20-50) during the fatiguing workbout. The time course of changes in these four neuromuscular responses suggested that the after-hyperpolarization theory could not explain the maintenance of force production, but Muscle Wisdom and the Onion Skin Scheme could. The findings of the current study suggested that the time course of changes in neuromuscular responses can provide insight in to the motor unit activation strategies used to maintain force production and allow for a greater understanding of the fatiguing process by identifying the time-points at which these neuromuscular parameters changed.


Subject(s)
Fatigue/physiopathology , Isometric Contraction , Muscles/physiology , Neurons/cytology , Electromyography , Humans , Male , Regression Analysis , Signal Processing, Computer-Assisted , Young Adult
14.
Eur J Appl Physiol ; 116(11-12): 2367-2374, 2016 Dec.
Article in English | MEDLINE | ID: mdl-27744584

ABSTRACT

PURPOSE: To compare the effects of two different resistance training programs, high intensity (INT) and high volume (VOL), on changes in isometric force (FRC), rate of force development (RFD), and barbell velocity during dynamic strength testing. METHODS: Twenty-nine resistance-trained men were randomly assigned to either the INT (n = 15, 3-5 RM, 3-min rest interval) or VOL (n = 14, 10-12 RM, 1-min rest interval) training group for 8 weeks. All participants completed a 2-week preparatory phase prior to randomization. Measures of barbell velocity, FRC, and RFD were performed before (PRE) and following (POST) the 8-week training program. Barbell velocity was determined during one-repetition maximum (1RM) testing of the squat (SQ) and bench press (BP) exercises. The isometric mid-thigh pull was used to assess FRC and RFD at specific time bands ranging from 0 to 30, 50, 90, 100, 150, 200, and 250 ms. RESULTS: Analysis of covariance revealed significant (p < 0.05) group differences in peak FRC, FRC at 30-200 ms, and RFD at 50-90 ms. Significant (p < 0.05) changes in INT but not VOL in peak FRC (INT: 9.2 ± 13.8 %; VOL: -4.3 ± 10.2 %), FRC at 30-200 ms (INT: 12.5-15.8 %; VOL: -1.0 to -4.3 %), and RFD at 50 ms (INT: 78.0 ± 163 %; VOL: -4.1 ± 49.6 %) were observed. A trend (p = 0.052) was observed for RFD at 90 ms (INT: 58.5 ± 115 %; VOL: -3.5 ± 40.1 %). No group differences were observed for the observed changes in barbell velocity. CONCLUSIONS: Results indicate that INT is more advantageous than VOL for improving FRC and RFD, while changes in barbell velocity during dynamic strength testing are similarly improved by both protocols in resistance-trained men.


Subject(s)
High-Intensity Interval Training/methods , Isometric Contraction/physiology , Muscle Strength/physiology , Muscle, Skeletal/physiology , Physical Exertion/physiology , Resistance Training/methods , Female , Humans , Male , Physical Fitness/physiology , Young Adult
15.
Exp Gerontol ; 84: 1-11, 2016 11.
Article in English | MEDLINE | ID: mdl-27521997

ABSTRACT

The purpose of this study was to investigate the effects of 8weeks at 6g per day of RAR CLA versus placebo on cognitive function and handgrip performance in older men and women. Sixty-five (43 women, 22 men) participants (mean±SD; age=72.4±5.9yrs; BMI=26.6±4.2kg·m-2) were randomly assigned to a RAR CLA (n=30: 10 men, 20 women) or placebo (PLA; high oleic sunflower oil; n=35: 12 men, 23 women) group in double-blind fashion and consumed 6g·d-1 of their allocated supplement for 8weeks. Before (Visit 1) and after supplementation (Visit 2), subjects completed the Serial Sevens Subtraction Test (S7), Trail Making Test Part A (TMA) and Part B (TMB), and Rey's Auditory Verbal Learning Test (RAVLT) to measure cognitive function. The RAVLT included 5, 15-item auditory word recalls (R1-5), an interference word recall (RB), a 6th word recall (R6), and a 15-item visual word recognition trial (RR). For handgrip performance, subjects completed maximal voluntary isometric handgrip strength (MVIC) testing before (MVICPRE) and after (MVICPOST) a handgrip fatigue test at 50% MVICPRE. Hand joint discomfort was measured during MVICPRE, MVICPOST, and the handgrip fatigue test. There were no treatment differences (p>0.05) for handgrip strength, handgrip fatigue, or cognitive function as measured by the Trail Making Test and Serial Seven's Subtraction Test in men or women. However, RAR CLA supplementation improved cognitive function as indicated by the RAVLT R5 in men. A qualitative examination of the mean change scores suggested that, compared to PLA, RAR CLA supplementation was associated with a small improvement in joint discomfort in both men and women. Longer-term studies are needed to more fully understand the potential impact of RAR CLA on cognitive function and hand joint discomfort in older adults, particularly in those with lower cognitive function.


Subject(s)
Aging , Cognition/drug effects , Hand Strength/physiology , Linoleic Acids, Conjugated/administration & dosage , Aged , Double-Blind Method , Fatigue , Female , Hand Joints/physiopathology , Humans , Male , Plant Oils/administration & dosage , Prospective Studies , Sex Factors , Sunflower Oil , United States
16.
J Strength Cond Res ; 30(11): 3051-3056, 2016 Nov.
Article in English | MEDLINE | ID: mdl-26982977

ABSTRACT

Wang, R, Hoffman, JR, Tanigawa, S, Miramonti, AA, La Monica, MB, Beyer, KS, Church, DD, Fukuda, DH, and Stout, JR. Isometric mid-thigh pull correlates with strength, sprint, and agility performance in collegiate rugby union players. J Strength Cond Res 30(11): 3051-3056, 2016-The purpose of this investigation was to examine the relationships between isometric mid-thigh pull (IMTP) force and strength, sprint, and agility performance in collegiate rugby union players. Fifteen members of a champion-level university's club rugby union team (mean ± SD: 20.67 ± 1.23 years, 1.78 ± 0.06 m, and 86.51 ± 14.18 kg) participated in this investigation. One repetition maximum (1RM) squat, IMTP, speed (40 m sprint), and agility (proagility test and T-test) were performed during 3 separate testing sessions. Rate of force development (RFD) and force output at 30, 50, 90, 100, 150, 200, and 250 milliseconds of IMTP, as well as the peak value were determined. Pearson product-moment correlation analysis was used to examine the relationships between these measures. Performance in the 1RM squat was significantly correlated to the RFD between 90 and 250 milliseconds from the start of contraction (r's ranging from 0.595 to 0.748), and peak force (r = 0.866, p ≤ 0.05). One repetition maximum squat was also correlated to force outputs between 90 and 250 milliseconds (r's ranging from 0.757 to 0.816, p ≤ 0.05). Sprint time over the first 5 m in the 40 m sprint was significantly (p ≤ 0.05) correlated with peak RFD (r = -0.539) and RFD between 30 and 50 milliseconds (r's = -0.570 and -0.527, respectively). Time for the proagility test was correlated with peak RFD (r = -0.523, p ≤ 0.05) and RFD between 30 and 100 milliseconds (r's ranging from -0.518 to -0.528, p's < 0.05). Results of this investigation indicate that IMTP variables are significantly associated with strength, agility, and sprint performance. Future studies should examine IMTP as a potential tool to monitor athletic performance during the daily training of rugby union players.


Subject(s)
Athletic Performance/physiology , Exercise Test , Isometric Contraction/physiology , Muscle Strength/physiology , Running/physiology , Athletes , Football/physiology , Humans , Male , Young Adult
17.
J Strength Cond Res ; 30(9): 2382-91, 2016 Sep.
Article in English | MEDLINE | ID: mdl-26937771

ABSTRACT

La Monica, MB, Fukuda, DH, Miramonti, AA, Beyer, KS, Hoffman, MW, Boone, CH, Tanigawa, S, Wang, R, Church, DD, Stout, JR, and Hoffman, JR. Physical differences between forwards and backs in American collegiate rugby players. J Strength Cond Res 30(9): 2382-2391, 2016-This study examined the anthropometric and physical performance differences between forwards and backs in a championship-level American male collegiate rugby team. Twenty-five male rugby athletes (mean ± SD; age 20.2 ± 1.6 years) were assessed. Athletes were grouped according to position as forwards (n = 13) and backs (n = 12) and were evaluated on the basis of anthropometrics (height, weight, percent body fat [BF%]), cross-sectional area (CSA), muscle thickness (MT), and pennation angle (PA) of the vastus lateralis (VL), maximal strength (1 repetition maximum [1RM] bench press and squat), vertical jump power, midthigh pull (peak force [PF] and peak rate of force development [PRFD]), maximal aerobic capacity (V[Combining Dot Above]O2peak), agility (pro agility, T test), speed (40-m sprint), and a tethered sprint (peak velocity [PV], time to peak velocity, distance covered, and step rate and length). Comparisons between forwards and backs were analyzed using independent t-tests with Cohen's d effect size. Forwards were significantly different from backs for body weight (90.5 ± 12.4 vs. 73.7 ± 7.1 kg, p < 0.01; d = 1.60), BF% (12.6 ± 4.2 vs. 8.8 ± 2.1%, p ≤ 0.05; d = 1.10), VL CSA (38.3 ± 9.1 vs. 28.7 ± 4.7 cm, p < 0.01; d = 1.26), 1RM bench press (121.1 ± 30.3 vs. 89.5 ± 20.4 kg, p ≤ 0.05; d = 1.17), 1RM squat (164.6 ± 43.0 vs. 108.5 ± 31.5 kg, p < 0.01; d = 1.42), PF (2,244.6 ± 505.2 vs. 1,654.6 ± 338.8 N, p < 0.01; d = 1.32), PV (5.49 ± 0.25 vs. 5.14 ± 0.37 m·s, p ≤ 0.05; d = 1.04), and step length (1.2 ± 0.1 vs. 1.1 ± 0.1 m, p ≤ 0.05; d = 0.80). V[Combining Dot Above]O2peak was significantly (p ≤ 0.05, d = -1.20) higher in backs (54.9 ± 3.9 ml·kg·min) than in forwards (49.4 ± 4.4 ml·kg·min). No differences in agility performance were found between position groups. The results of this study provide descriptive information on anthropometric and performance measures on American male collegiate championship-level rugby players offering potential standards for coaches to use when developing or recruiting players.


Subject(s)
Athletic Performance/physiology , Football/physiology , Muscle Strength/physiology , Muscle, Skeletal/physiology , Physical Fitness/physiology , Adolescent , Anthropometry/methods , Athletes , Athletic Performance/statistics & numerical data , Cross-Sectional Studies , Exercise/physiology , Exercise Test , Humans , Male , United States , Universities , Young Adult
18.
J Strength Cond Res ; 30(2): 400-6, 2016 Feb.
Article in English | MEDLINE | ID: mdl-26284681

ABSTRACT

This study examined the influence of recovery time on fatigue indices, performance (total work [TW], peak power [PP], and mean power [MP]), and oxygen consumption during repeated sprint ability (RSA) on a cycle ergometer. Eight recreationally-trained men performed 3 RSA protocols consisting of 10 × 6 s sprints with 12 s, 18 s, and 24 s rest intervals between each sprint. Fatigue indices were determined as percent decrement (%Dec) and rate of decline using either a log transform method or standard slope approach for TW, PP, and MP during respective RSA protocols. The maximal VO2 value in response to given sprint intervals and the minimal VO2 value in response to given rest periods (VO2 work and VO2 rest, respectively) were recorded. A repeated measures analysis of variance was used to analyze all variables. Average VO2 work was not different among rest interval trials. Average VO2 rest with 12 s rest was greater than 18 s and 24 s (2.16 ± 0.17 L · min(-1), 1.91 ± 0.18 L · min(-1), 1.72 ± 0.15 L · min(-1), respectively), while 18 s was greater than 24 s. Average TW and MP were greater with 24 s rest than 12 s (4,604.44 ± 915.98 J vs. 4,305.46 ± 727.17 J, respectively), with no differences between RSA protocols for PP. No differences in %Dec were observed. Both methods of calculating rates of decline per sprint for PP and TW were greater during 12 s than 18 s or 24 s. Since changes were only noted between the 12 s and 24 s protocols, a 6 s differential in rest intervals may not be enough to elicit alterations in TW, PP, MP, or %Dec in RSA performance. Rate of decline may be a more sensitive measure of fatigue than %Dec.


Subject(s)
Exercise Test/methods , Fatigue/prevention & control , Rest/psychology , Running/physiology , Adult , Humans , Male , Oxygen Consumption/physiology , Recovery of Function/physiology , Young Adult
19.
J Sports Med Phys Fitness ; 56(10): 1093-1102, 2016 Oct.
Article in English | MEDLINE | ID: mdl-26329841

ABSTRACT

BACKGROUND: To test if the critical power (CP) concept can be utilized to determine the critical rest interval (CRI) using repeated sprint ability (RSA) testing with varying work-to-rest ratios. METHODS: Twelve recreationally trained men (mean±SD; age 24.1±3.6 years) completed a graded exercise test and three RSA protocols with 6-second maximal sprints and varying rest intervals (12-36 s) on a cycle ergometer to determine CRI. Intermittent critical power (ICP) was calculated through the linear total work (TW) and time-to-exhaustion (TTE) relationship, whereas CRI was estimated using average work per sprint and ICP. Validation trials above and below CRI were conducted to evaluate physiological response. Repeated measures analysis of variance were used to analyze variables from RSA trials and changes in blood lactate, oxygen uptake (V̇O2), heart rate (HR), peak power, and TW throughout the validation trials. RESULTS: Blood lactate, average V̇O2, V̇O2peak, and heart rate were significantly greater below CRI (8.94±4.89 mmol/L, 2.05±0.36 L/min, 2.84±0.48 L/min, and 151.14±18.46 bpm, respectively) when compared to above CRI (6.56±3.45 mmol/L, 1.78±0.26 L/min, 2.61±0.43 L/min, and 138.14±17.51 bpm). Significant interactions were found between above and below CRI for minimal V̇O2 response and maximal HR response, which were consistent with the heavy and severe exercise intensity domains. CONCLUSIONS: The use of the work-time relationship determined from RSA testing with varying rest intervals can be used to determine CRI and may distinguish between physiological responses related to exercise intensity domains.


Subject(s)
Exercise Test , Rest/physiology , Running/physiology , Adolescent , Adult , Cross-Over Studies , Fatigue , Homeostasis , Humans , Male , Oxygen Consumption/physiology , Surveys and Questionnaires , Young Adult
20.
J Strength Cond Res ; 30(3): 626-34, 2016 Mar.
Article in English | MEDLINE | ID: mdl-26418369

ABSTRACT

This study investigated the effects of high-intensity interval training (HIIT) and ß-hydroxy-ß-methylbutyric free acid (HMB) supplementation on physical working capacity at the onset of neuromuscular fatigue threshold (PWC(FT)). Thirty-seven participants (22 men, 15 women; 22.8 ± 3.4 years) completed an incremental cycle ergometer test (graded exercise test [GXT]); electromyographic amplitude from the right vastus lateralis was recorded. Assessments occurred preceding (PRE) and after 4 weeks of supplementation (POST). Participants were randomly assigned to control (C, n = 9), placebo (P, n = 14), or supplementation (S, n = 14) groups. Both P and S completed 12 HIIT sessions, whereas C maintained normal diet and activity patterns. The PWC(FT) (W) was determined using the maximal perpendicular distance (D(MAX)) method. Electromyographic amplitude (µVrms) over time was used to generate a cubic regression. Onset of fatigue (TF) was the x-value of the point on the regression that was at D(MAX) from a line between the first and last data points. The PWC(FT) was estimated using TF and GXT power-output increments. The 2-way analysis of variance (ANOVA) (group × time) resulted in a significant interaction for PWC(FT) (F = 6.69, p = 0.004). Post hoc analysis with 1-way ANOVA resulted in no difference in PWC(FT) among groups at PRE (F = 0.87, p = 0.43); however, a difference in PWC(FT) was shown for POST (F = 5.46, p = 0.009). Post hoc analysis among POST values revealed significant differences between S and both P (p = 0.034) and C (p = 0.003). No differences (p = 0.226) were noted between P and C. Paired samples t-tests detected significant changes after HIIT for S (p < 0.001) and P (p = 0.016), but no change in C (p = 0.473). High-intensity interval training increased PWC(FT), but HMB with HIIT was more effective than HIIT alone. Furthermore, it seems that adding HMB supplementation with HIIT in untrained men and women may further improve endurance performance measures.


Subject(s)
Dietary Supplements , Muscle Fatigue/physiology , Physical Conditioning, Human/methods , Physical Conditioning, Human/physiology , Quadriceps Muscle/physiology , Valerates/administration & dosage , Adult , Double-Blind Method , Electromyography , Exercise Test , Exercise Tolerance , Female , Humans , Male , Muscle Fatigue/drug effects , Physical Exertion/physiology , Young Adult
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