A Retrospective Analysis of Southeastern U.S. Police Recruit Health and Fitness From 4 Points in Time Within a 16-Year Period: Implications for Physical Fitness Training.

ABSTRACT: Gonzales, SM, Orr, RM, Coburn, JW, Hoffmann, MD, Kennedy, K, Dawes, JJ, and Lockie, RG. A retrospective analysis of southeastern U.S. police recruit health and fitness from 4 points in time within a 16-year period: Implications for physical fitness training. J Strength Cond Res 38(6): 1118-1126, 2024-Drawing from the general population for its recruiting needs, police departments often employ academy curricula to improve a recruit's fitness so they can perform occupational tasks. Recently, obesity and physical inactivity have increased in the general population, potentially influencing the health and fitness of incoming recruits. This study involved a retrospective, cross-sectional analysis of health and fitness data of police recruits. Data from 1 police department in southeastern United States were analyzed at 4 specific time points, splitting the recruits into natural immerging groups; 2003 (n = 93), 2006 (n = 137), 2009 (n = 74), and 2019 (n = 242). Health and fitness data for all recruits included age, height, body mass, and body mass index (BMI); systolic and diastolic blood pressure (BP); sit-and-reach; combined grip strength; push-ups and sit-ups completed in 60 seconds; physical ability test time; and 2.4-km run time. Several univariate analyses, with sex and age as covariates (analyses of covariance), and a Bonferroni's post hoc, determined whether there were significant between-group differences. Effect sizes (d) were also calculated. Key results demonstrated that 2019 recruits were heavier than the recruits in 2006 and 2009 (p ≤ 0.032; d = 0.14-0.38); had a greater BMI (p ≤ 0.028; d = 0.24-0.75) and systolic BP (p < 0.001; d = 0.47-0.65), and lesser sit-and-reach distance (p ≤ 0.020; d = 0.26-0.46), than all recruit groups; completed fewer sit-up repetitions than the recruits in 2006 and 2009 (p ≤ 0.025; d = 0.42-0.48); and were slower in the 2.4-km run than the recruits in 2006 (p = 0.009; d = 0.36). Police training staff may need to address lesser health (BMI, BP) and fitness (hamstring flexibility, abdominal endurance, aerobic fitness) in incoming recruits.

Effects of Percussive Massage Treatments on Symptoms Associated with Eccentric Exercise-Induced Muscle Damage.

Percussive massage (PM) is an emerging recovery treatment despite the lack of research on its effects post-eccentric exercise (post-EE). This study investigated the effects of PM treatments (immediately, 24, 48, and 72 h post-EE) on the maximal isometric torque (MIT), range of motion (ROM), and an 11-point numerical rating scale (NRS) of soreness of the nondominant arm's biceps brachii from 24-72 h post-EE. Seventeen untrained, college-aged subjects performed 60 eccentric elbow flexion actions with their nondominant arms. Nine received 1 minute of PM, versus eight who rested quietly (control [CON]). In order, NRS, ROM, and MIT (relative to body mass) were collected pre-eccentric exercise (pre-EE) and after treatment (AT) at 24, 48, and 72 h post-EE. NRS was also collected before treatment (BT). Electromyographic (EMG) and mechanomyographic (MMG) amplitudes were collected during the MIT and normalized to pre-EE. There were no interactions for MIT, EMG, or MMG, but there were interactions for ROM and NRS. For ROM, the PM group had higher values than the CON 24-72 h by ~6-8°, a faster return to pre-EE (PM: 48 h, CON: 72 h), and exceeded their pre-EE at 72 h by ~4°. The groups' NRS values did not differ BT 24-72 h; however, the PM group lowered their NRS from BT to AT within every visit by ~1 point per visit, which resulted in them having lower values than the CON from 24-72 h by ~2-3 points. Additionally, the PM group returned their NRS to pre-EE faster than the CON (PM: BT 72 h, CON: never). In conclusion, PM treatments may improve ROM without affecting isometric strength or muscle activation 24-72 h post-EE. Although the PM treatments did not enhance the recovery from delayed onset muscle soreness until 72 h, they consistently provided immediate, temporary relief when used 24-72 h post-EE.

Hip and Knee Kinetics During a Back Squat and Deadlift.

ABSTRACT: Choe, KH, Coburn, JW, Costa, PB, and Pamukoff, DN. Hip and knee kinetics during a back-squat and deadlift. J Strength Cond Res 35(5): 1364-1371, 2021-The back-squat and deadlift are performed to improve hip and knee extensor function. The purpose of this study was to compare lower extremity joint kinetics (peak net joint moments [NJMs] and positive joint work [PJW]) between the back-squat and deadlift. Twenty-eight resistance-trained subjects (17 men: 23.7 ± 4.3 years, 1.76 ± 0.09 m, 78.11 ± 10.91 kg; 11 women: 23.0 ± 1.9 years, 1.66 ± 0.06 m, 65.36 ± 7.84 kg) were recruited. One repetition maximum (1RM) testing and biomechanical analyses occurred on separate days. Three-dimensional biomechanics of the back-squat and deadlift were recorded at 70 and 85% 1RM for each exercise. The deadlift demonstrated larger hip extensor NJM than the back-squat {3.59 (95% confidence interval [CI]: 3.30-3.88) vs. 2.98 (95% CI: 2.72-3.23) Nm·kg-1, d = 0.81, p < 0.001}. However, the back-squat had a larger knee extensor NJM compared with the deadlift (2.14 [95% CI: 1.88-2.40] vs. 1.18 [95% CI: 0.99-1.37] Nm·kg-1, d = 1.44 p < 0.001). More knee PJW was performed during the back-squat compared with the deadlift (1.85 [95% CI: 1.60-2.09] vs. 0.46 [95% CI: 0.35-0.58] J·kg-1, d = 2.10, p < 0.001). However, there was more hip PJW during the deadlift compared with the back-squat (3.22 [95% CI: 2.97-3.47] vs. 2.37 [95% CI: 2.21-2.54] J·kg-1, d = 1.30, p < 0.001). Larger hip extensor NJM and PJW during the deadlift suggest that individuals targeting their hip extensors may yield greater benefit from the deadlift compared with the back-squat. However, larger knee extensor NJM and PJW during the back-squat suggest that individuals targeting their knee extensor muscles may benefit from incorporating the back-squat compared with the deadlift.

The Evolution of the Physical Work Capacity at the Fatigue Threshold Test: Past, Present, and Future.

ABSTRACT: Feldpausch, JE, Blok, AL, Frederick, EL, Coburn, JW, and Malek, MH. The evolution of the physical work capacity at the fatigue threshold test: past, present, and future. J Strength Cond Res 35(12): 3529-3536, 2021-The assessment of neuromuscular fatigue using surface electromyography has evolved over the past 40 years while maintaining some of the original key features. In this mini-review article, the goal will be to briefly present a history and systems of the physical working capacity at the fatigue threshold (PWCFT). In addition, we will discuss studies that have investigated the effect of different interventions such as supplementation, exercise, and cognitive fatigue to examine what stimuli influence the PWCFT. The latter section of this mini-review will discuss future studies that may provide additional information related to the underlying physiological mechanism(s) that influences the PWCFT. We will conclude with the practical application of PWCFT in health and sports settings.

Caffeine's Effects on an Upper-Body Resistance Exercise Workout.

Salatto, RW, Arevalo, JA, Brown, LE, Wiersma, LD, and Coburn, JW. Caffeine's effects on an upper-body resistance exercise workout. J Strength Cond Res 34(6): 1643-1648, 2020-The purpose of this study was to examine the effects of caffeine on an upper-body resistance exercise workout. Fifteen men (mean ± SD: age, 23.1 ± 1.9 years; body mass, 89.1 ± 13.9 kg; height, 175 ± 6.1 cm) volunteered to come to the laboratory 3 times. During visit 1, 1-repetition maximum (RM) values were determined for the barbell bench press, incline barbell bench press, and dumbbell bench press exercises. For visit 2, subjects consumed either 800-mg caffeine or a placebo. Subjects then completed 3 sets to failure of each exercise using 80% of their 1RM. Visit 3 was the same as visit 2; however, participants consumed the opposite treatment as visit 2. Various perceptual measures were recorded before, during, and after the workouts. The results indicated that participants completed significantly more repetitions per set for the barbell bench press (4.80 ± 2.66) and incline barbell bench press (4.91 ± 2.29) in the caffeine condition compared with the placebo condition (4.42 ± 2.56 and 4.36 ± 2.11, respectively). Higher arousal scores were found in the caffeine condition. For vigor, participants reported higher scores with caffeine before warming up (caffeine = 10.20 ± 4.11, placebo = 6.20 ± 3.23) and mid workout (caffeine = 13.53 ± 2.29, placebo = 11.13 ± 2.79). These results suggest that caffeine has an ergogenic effect on strength workout performance due, at least in part, to positive effects on workout perception. Athletes and recreational lifters may want to consider the ingestion of caffeine before a resistance exercise workout.

Epigenetic Responses to Acute Resistance Exercise in Trained vs. Sedentary Men.

Bagley, JR, Burghardt, KJ, McManus, R, Howlett, B, Costa, PB, Coburn, JW, Arevalo, JA, Malek, MH, and Galpin, AJ. Epigenetic responses to acute resistance exercise in trained vs. sedentary men. J Strength Cond Res 34(6): 1574-1580, 2020-Acute resistance exercise (RE) alters DNA methylation, an epigenetic process that influences gene expression and regulates skeletal muscle adaptation. This aspect of cellular remodeling is poorly understood, especially in resistance-trained (RT) individuals. The study purpose was to examine DNA methylation in response to acute RE in RT and sedentary (SED) young men, specifically targeting genes responsible for metabolic, inflammatory, and hypertrophic muscle adaptations. Vastus lateralis biopsies were performed before (baseline), 30 minutes after, and 4 hours after an acute RE bout (3 × 10 repetitions at 70% 1 repetition maximum [1RM] leg press and leg extension) in 11 RT (mean ± SEM: age = 26.1 ± 1.0 years; body mass = 84.3 ± 0.2 kg; leg press 1RM = 412.6 ± 25.9 kg) and 8 SED (age = 22.9 ± 1.1 years; body mass = 75.6 ± 0.3 kg; leg press 1RM = 164.8 ± 22.5 kg) men. DNA methylation was analyzed through methylation sensitive high-resolution melting using real-time polymerase chain reaction. Separate 2 (group) × 3 (time) repeated-measures analyses of variance and analyses of covariance were performed to examine changes in DNA methylation for each target gene. Results showed that acute RE (a) hypomethylated LINE-1 (measure of global methylation) in RT but not SED, (b) hypermethylated metabolic genes (GPAM and SREBF2) in RT, while lowering SREBF2 methylation in SED, and (c) did not affect methylation of genes associated with inflammation (IL-6 and TNF-α) or hypertrophy (mTOR and AKT1). However, basal IL-6 and TNF-α were lower in SED compared with RT. These findings indicate the same RE stimulus can illicit different epigenetic responses in RT vs. SED men and provides a molecular mechanism underpinning the need for differential training stimuli based on subject training backgrounds.

Muscle health and performance in monozygotic twins with 30 years of discordant exercise habits.

INTRODUCTION: Physical health and function depend upon both genetic inheritance and environmental factors (e.g., exercise training). PURPOSE: To enhance the understanding of heritability/adaptability, we explored the skeletal muscle health and physiological performance of monozygotic (MZ) twins with > 30 years of chronic endurance training vs. no specific/consistent exercise. METHODS: One pair of male MZ twins (age = 52 years; Trained Twin, TT; Untrained Twin, UT) underwent analyses of: (1) anthropometric characteristics and blood profiles, (2) markers of cardiovascular and pulmonary health, and (3) skeletal muscle size, strength, and power and molecular markers of muscle health. RESULTS: This case study represents the most comprehensive physiological comparison of MZ twins with this length and magnitude of differing exercise history. TT exhibited: (1) lower body mass, body fat%, resting heart rate, blood pressure, cholesterol, triglycerides, and plasma glucose, (2) greater relative cycling power, anaerobic endurance, and aerobic capacity (VO2max), but lower muscle size/strength and poorer muscle quality, (3) more MHC I (slow-twitch) and fewer MHC IIa (fast-twitch) fibers, (4) greater AMPK protein expression, and (5) greater PAX7, IGF1Ec, IGF1Ea, and FN14 mRNA expression than UT. CONCLUSIONS: Several measured differences are the largest reported between MZ twins (TT expressed 55% more MHC I fibers, 12.4 ml/kg/min greater VO2max, and 8.6% lower body fat% vs. UT). These data collectively (a) support utilizing chronic endurance training to improve body composition and cardiovascular health and (b) suggest the cardiovascular and skeletal muscle systems exhibit greater plasticity than previously thought, further highlighting the importance of studying MZ twins with large (long-term) differences in exposomes.

Relationships and Reliability Between a Drive Block Test and Traditional Football Performance Tests in High School Offensive Line Players.

Collins, KS, Coburn, JW, Galpin, AJ, and Lockie, RG. Relationships and reliability between a drive block test and traditional football performance tests in high school offensive line players. J Strength Cond Res 32(12): 3432-3441, 2018-The offensive line (OL) is a specialized football position responsible for blocking tasks. Little research exists on OL-specific movements and relationships to performance tests in high school players. This study investigated the reliability of the average and peak velocity (avgV, peakV) and momentum (avgM, peakM) of a drive block test (DBT) in 15 high school OL and relationships to performance tests. A linear position transducer attached to the OL waist measured the DBT from a 3-point stance into a blocking pad. Linear speed was measured by a 36.58-m sprint. Change-of-direction (COD) ability was measured by the pro-agility shuttle (first COD, second COD, and total time) and COD deficit from the first (COD deficit 1) and second COD (COD deficit 2) of the pro-agility shuttle. Vertical jump, standing broad jump (SBJ), and 1 repetition maximum (1RM) back squat were also measured. Pearson's correlations (p < 0.05) investigated relationships between the DBT and performance tests. Intraclass correlation coefficients (ICCs), dependent t-tests, and coefficient of variation (CV) assessed DBT reliability. Drive block test variables were reliable (ICC > 0.90; CV = 6.46-8.29%) and correlated with the second pro-agility shuttle COD and COD deficit 2 (r = -0.515 to -0.721). One repetition maximum back squat correlated with avgM and peakM (r = 0.551-0.582); SBJ correlated with avgV and peakV (r = 0.557-0.571). The pro-agility shuttle splits, COD deficit, and SBJ may provide useful information about DBT qualities important for high school OL. It is recommended high school OL training focus on strength, COD performance, and jumping ability to aid drive block performance.

Effects of Foam Rolling on Range of Motion, Peak Torque, Muscle Activation, and the Hamstrings-to-Quadriceps Strength Ratios.

Madoni, SN, Costa, PB, Coburn, JW, and Galpin, AJ. Effects of foam rolling on range of motion, peak torque, muscle activation, and the hamstrings-to-quadriceps strength ratios. J Strength Cond Res 32(7): 1821-1830, 2018-To examine the effects of foam rolling (FR) on range of motion (ROM), peak torque (PT), hamstrings-to-quadriceps (H:Q) ratios, and muscle activation. Twenty-two recreationally active women (mean age ± SD = 21.55 ± 1.82 years, 161.91 ± 6.58 cm, 61.47 ± 10.54 kg) volunteered for this study. Participants performed pre- and posttests analyzing PT and surface electromyography (EMG) of their dominant limb, completing maximal knee extension and flexion at 3 different velocities. Participants foam rolled the hamstrings muscles or sat for the control condition between the pre- and posttests. Hamstrings ROM increased in the FR condition from (mean ± SE) 123.23 ± 3.49 to 126.41 ± 3.62° (p < 0.001) and decreased in the control condition from 118.82 ± 4.25 to 117.95 ± 4.29° (p = 0.013). Concentric hamstrings PT and conventional H:Q ratios decreased after both conditions, with smaller decreases after FR (p ≤ 0.05). No significant changes were found for eccentric hamstrings PT, eccentric hamstrings EMG, or functional H:Q ratios (p > 0.05). Foam rolling resulted in greater changes in hamstrings ROM without creating a deficit in PT or muscle activation when compared with the control group. When compared with other methods of stretching, FR may be beneficial in increasing ROM without decreasing functional H:Q ratios.

Skeletal Muscle Fatigability and Myosin Heavy Chain Fiber Type in Resistance Trained Men.

Bagley, JR, McLeland, KA, Arevalo, JA, Brown, LE, Coburn, JW, and Galpin, AJ. Skeletal muscle fatigability and myosin heavy chain fiber type in resistance trained men. J Strength Cond Res 31(3): 602-607, 2017-Forty years ago, Thorstensson and Karlsson in 1976 described the link between muscle fatigability and fiber type, finding that more fast-twitch fibers were associated with a quicker onset of quadriceps fatigue. This provided the foundation for the Classic Thorstensson Test of fatigability and subsequent noninvasive fiber type prediction equation. This equation was developed with data from recreationally active (REC) men but has been implemented in participants with heterogeneous physical activity/exercise backgrounds. The accuracy of this approach in resistance trained (RET) men has not been established. Moreover, muscle fiber typing techniques have evolved considerably since this seminal work. Therefore, we reexamined this relationship using RET men and a more sensitive fiber typing method (single fiber myosin heavy chain [MHC] isoform classification). Fifteen RET men (age = 24.8 ± 1.3 years) performed maximal knee extensions (via isokinetic dynamometry) to determine peak torque (PT) and quadriceps fatigue percentage (FP) after 30 and 50 repetitions. Vastus lateralis (VL) single fiber MHC type was determined and fibers were grouped as %Fast (expressing MHC IIa, IIa/IIX, or IIx; no MHC I containing fibers). Resistance trained men exhibited 46% greater PT (RET = 207 ± 28 N·m vs. REC = 130 ± 8 N·m) and 28% more %Fast (RET = 61 ± 4% vs. REC = 44 ± 4%) than REC men. Additionally, RET men had a relatively homogeneous FP (64 ± 1%) ranging from 53 to 72%. No relationship was found between FP and MHC fiber type (R = 0.01, p > 0.05). The Classic Thorstensson Test may not accurately estimate VL fiber type composition in RET men, highlighting the (a) unique phenotypical/functional adaptations induced by chronic RET and (b) the need for more sensitive cellular/molecular analyses in RET muscle.

Comparison of Olympic and Hexagonal Barbells With Midthigh Pull, Deadlift, and Countermovement Jump.

Malyszek, KK, Harmon, RA, Dunnick, DD, Costa, PB, Coburn, JW, and Brown, LE. Comparison of olympic and hexagonal barbells with midthigh pull, deadlift, and countermovement jump. J Strength Cond Res 31(1): 140-145, 2017-Those training for strength and power commonly use different bars and different lifts. The hexagonal barbell (HBar) and Olympic barbell (OBar) are frequently used training implements, and the midthigh pull (MTP) and deadlift (DL) are 2 popular exercises. Therefore, the purpose of this study was to compare force between an HBar and OBar for a MTP, DL, and countermovement jump (CMJ). Twenty resistance-trained men (age = 24.05 ± 2.09 years, ht = 178.07 ± 7.05 cm, mass = 91.42 ± 14.44 kg) volunteered to participate and performed MTP and DL using both bars and a CMJ. Joint angles were recorded for all pulls and the bottom position of the CMJ. Peak ground reaction force (PGRF) was greater in the MTP (3,186.88 ± 543.53 N) than DL (2,501.15 ± 404.04 N) but not different between bars. Midthigh pull joint angles were more extended than DL, and the strongest correlations between isometric and dynamic performance were seen between DL PGRF and CMJ impulse (OBar r = 0.85; HBar r = 0.84). These findings are likely because of the different anatomical characteristics between the MTP and DL and the similarity in joint angles between the DL and CMJ. Therefore, the DL may be an optimal choice for athletes in jump-dependent sports, regardless of bar.

Influence of Rest Intervals After Assisted Sprinting on Bodyweight Sprint Times in Female Collegiate Soccer Players.

Nealer, AL, Dunnick, DD, Malyszek, KK, Wong, MA, Costa, PB, Coburn, JW, and Brown, LE. Influence of rest intervals after assisted sprinting on bodyweight sprint times in female collegiate soccer players. J Strength Cond Res 31(1): 88-94, 2017-Speed is a crucial element an athlete must possess to be successful. In soccer, the ability to accelerate faster than your opponent can result in being first to reach a ball on a breakaway or stopping a counter attack. A unique way to train explosive movements is to evoke postactivation potentiation (PAP) in the working muscles. Traditionally, an overload stimulus with a long rest period is used, but a model using an overspeed stimulus with shorter rest periods is less understood. Therefore, the purpose of this study was to determine the acute effects of varied rest intervals after assisted sprinting on bodyweight sprint time. Twenty-four female soccer players were split into 2 groups: recreational (n:11; age:20 ± 1.67 year; ht:162.30 ± 4.35 cm; mass:61.02 ± 8.78 kg) and collegiate athletes (n:13; age:19.76 ± 0.83 year; ht:166.85 ± 5.98 cm; mass:61.23 ± 3.77 kg). All participants attended 5 separate sessions, performed a dynamic warm up, then executed one 20 m sprint (with 5 m splits) at 30% bodyweight assistance (BWA). They then rested for 30 seconds, 1, 2, or 4 minutes in random order, followed by one bodyweight sprint with no BWA. Baseline sprint times were measured without BWA on the initial session of testing. Results revealed no difference in sprint time for the full 20 m distance in either group. However, sprint time was significantly decreased for the 0-5 m split only for the athletes after 1 minute (1.15 ± 0.06 second) and 2 minute (1.16 ± 0.06 second) rest compared with baseline (1.21 ± 0.04 second). Therefore, trained athletes should rest 1 or 2 minutes after 30% BWA supramaximal sprinting for increased bodyweight sprint speed.

Sled Towing Acutely Decreases Acceleration Sprint Time.

Wong, MA, Dobbs, IJ, Watkins, C, Barillas, SR, Lin, A, Archer, DC, Lockie, RG, Coburn, JW, and Brown, LE. Sled towing acutely decreases acceleration sprint time. J Strength Cond Res 31(11): 3046-3051, 2017-Sled towing is a common form of overload training in sports to develop muscular strength for sprinting. This type of training leads to acute and chronic outcomes. Acute training potentially leads to postactivation potentiation (PAP), which is when subsequent muscle performance is enhanced after a preload stimulus. The purpose of this study was to determine differences between rest intervals after sled towing on acute sprint speed. Twenty healthy recreationally trained men (age = 22.3 ± 2.4 years, height = 176.95 ± 5.46 cm, mass = 83.19 ± 11.31 kg) who were currently active in a field sport twice a week for the last 6 months volunteered to participate. A maximal 30-meter (m) baseline (BL) body mass (BM) sprint was performed (with splits at 5, 10, 20, and 30 m) followed by 5 visits where participants sprinted 30 m towing a sled at 30% BM then rested for 2, 4, 6, 8, or 12 minutes. They were instructed to stand still during rest times. After the rest interval, they performed a maximal 30-m post-test BM sprint. Analysis of variance (ANOVA) revealed that post sled tow BM sprint times (4.47 ± 0.21 seconds) were less than BL times (4.55 ± 0.18 seconds) on an individualized rest interval basis. A follow-up 2 × 4 ANOVA showed that this decrease occurred only in the acceleration phase over the first 5 m (BL = 1.13 ± 0.08 seconds vs. Best = 1.08 ± 0.08 seconds), which may be the result of PAP and the complex relationship between fatigue and potentiation relative to the intensity of the sled tow and the rest interval. Therefore, coaches should test their athletes on an individual basis to determine optimal rest time after a 30-m 30% BM sled tow to enhance acute sprint speed.

Determination of Vertical Jump as a Measure of Neuromuscular Readiness and Fatigue.

Watkins, CM, Barillas, SR, Wong, MA, Archer, DC, Dobbs, IJ, Lockie, RG, Coburn, JW, Tran, TT, and Brown, LE. Determination of vertical jump as a measure of neuromuscular readiness and fatigue. J Strength Cond Res 31(12): 3305-3310, 2017-Coaches closely monitor training loads and periodize sessions throughout the season to create optimal adaptations at the proper time. However, only monitoring training loads ignores the innate physiological stress each athlete feels individually. Vertical jump (VJ) is widely used as a measure of lower-body power, and has been used in postmatch studies to demonstrate fatigue levels. However, no pretraining monitoring by VJ performance has been previously studied. Therefore, the purpose of this study was to determine the sensitivity of VJ as a measure of readiness and fatigue on a daily sessional basis. Ten healthy resistance-trained males (mass = 91.60 ± 13.24 kg; height = 179.70 ± 9.23 cm; age = 25.40 ± 1.51 years) and 7 females (mass = 65.36 ± 12.29 kg; height = 162.36 ± 5.75 cm; age = 25.00 ± 2.71 years) volunteered to participate. Vertical jump and BRUNEL Mood Assessment (BAM) were measured 4 times: pre-workout 1, post-workout 1, pre-workout 2, and post-workout 2. Workout intensity was identical for both workouts, consisting of 4 sets of 5 repetitions for hang cleans, and 4 sets of 6 repetitions for push presses at 85% 1 repetition maximum (1RM), followed by 4 sets to failure of back squats (BSs), Romanian deadlift, and leg press at 80% 1RM. The major finding was that VJ height decrement (-8.05 ± 9.65 cm) at pre-workout 2 was correlated (r = 0.648) with BS volume decrement (-27.56 ± 24.56%) between workouts. This is important for coaches to proactively understand the current fatigue levels of their athletes and their readiness to resistance training.

Acute Effects of Eccentric Overload on Concentric Front Squat Performance.

Munger, CN, Archer, DC, Leyva, WD, Wong, MA, Coburn, JW, Costa, PB, and Brown, LE. Acute effects of eccentric overload on concentric front squat performance. J Strength Cond Res 31(5): 1192-1197, 2017-Eccentric overload is used to enhance performance. The purpose of this study was to investigate the acute effects of eccentric overload on concentric front squat performance. Twenty resistance-trained men (age = 23.80 ± 1.82 years, height = 176.95 ± 5.21 cm, mass = 83.49 ± 10.43 kg, 1 repetition maximum [1RM] front squat = 131.02 ± 21.32 kg) volunteered. A dynamic warm-up and warm-up sets of front squat were performed. Eccentric hooks were added to the barbell. They descended for 3 seconds, until eccentric hooks released, and performed the concentric phase as fast as possible. There were 3 randomly ordered conditions with the concentric phase always at 90% 1RM and the eccentric phase at 105, 110, and 120% of 1RM. Two repetitions were performed for each condition. A repeated measures analysis of variance was used to determine differences. For peak velocity, there were main effects for time and condition (p < 0.05), where post (1.01 ± 0.10 m·s) was greater than pre (0.96 ± 0.11 m·s) and 120% (1.03 ± 1.11 m·s) was greater than 105% (0.99 ± 0.13 m·s). For peak power, there was a main effect for condition where 120% (2,225.00 ± 432.37 W) was greater than 105% (2,021.84 ± 563.53 W). For peak ground reaction force, there were main effects for time and condition, where post was greater than pre and 120% was greater than 105%. For the rate of force development, there was no interaction or main effects. Eccentric overload enhanced concentric velocity and power; therefore, it can be used by strength coaches and athletes during the power phase of a training program. It can also be used to prescribe supramaximal loads and could be a tool to supplement the clean exercise because the front squat is a precursor.

An Examination of Muscle Activation and Power Characteristics While Performing the Deadlift Exercise With Straight and Hexagonal Barbells.

The deadlift exercise is commonly performed to develop strength and power, and to train the lower-body and erector spinae muscle groups. However, little is known about the acute training effects of a hexagonal barbell vs. a straight barbell when performing deadlifts. Therefore, the purpose of this study was to examine the hexagonal barbell in comparison with the straight barbell by analyzing electromyography (EMG) from the vastus lateralis, biceps femoris, and erector spinae, as well as peak force, peak power, and peak velocity using a force plate. Twenty men with deadlifting experience volunteered to participate in the study. All participants completed a 1 repetition maximum (1RM) test with each barbell on 2 separate occasions. Three repetitions at 65 and 85% 1RM were performed with each barbell on a third visit. The results revealed that there was no significant difference for 1RM values between the straight and hexagonal barbells (mean ± SD in kg = 181.4 ± 27.3 vs. 181.1 ± 27.6, respectively) (p > 0.05). Significantly greater normalized EMG values were found from the vastus lateralis for both the concentric (1.199 ± 0.22) and eccentric (0.879 ± 0.31) phases of the hexagonal-barbell deadlift than those of the straight-barbell deadlift (0.968 ± 0.22 and 0.559 ± 1.26), whereas the straight-barbell deadlift led to significantly greater EMG values from the bicep femoris during the concentric phase (0.835 ± 0.19) and the erector spinae (0.753 ± 0.28) during the eccentric phase than the corresponding values for the hexagonal-barbell deadlift (0.723 ± 0.20 and 0.614 ± 0.21) (p ≤ 0.05). In addition, the hexagonal-barbell deadlift demonstrated significantly greater peak force (2,553.20 ± 371.52 N), peak power (1,871.15 ± 451.61 W), and peak velocity (0.805 ± 0.165) values than those of the straight-barbell deadlift (2,509.90 ± 364.95 N, 1,639.70 ± 361.94 W, and 0.725 ± 0.138 m·s, respectively) (p ≤ 0.05). These results suggest that the barbells led to different patterns of muscle activation and that the hexagonal barbell may be more effective at developing maximal force, power, and velocity.

Electromyographic and Force Plate Analysis of the Deadlift Performed With and Without Chains.

The purpose of this study was to determine the effects of deadlift chain variable resistance on surface electromyography (EMG) of the gluteus maximus, erector spinae, and vastus lateralis muscles, ground reaction forces (GRFs), and rate of force development (RFD). Thirteen resistance-trained men (24.0 ± 2.1 years, 179.3 ± 4.8 cm, 87.0 ± 10.6 kg) volunteered for the study. On day 1, subjects performed 1 repetition maximum (1RM) testing of the deadlift exercise. On day 2, subjects performed one set of 3 repetitions with a load of 85% 1RM with chains (CH) and without chains (NC). The order of the CH and NC conditions was randomly determined for each subject. For the CH condition, the chains accounted for approximately 20% (19.9 ± 0.6%) of the 85% 1RM load, matched at the top of the lift. Surface EMG was recorded to differentiate muscle activity between conditions (CH, NC), range of motion (ROM; bottom, top), and phase (concentric, eccentric). Peak GRFs and RFD were measured using a force plate. Electromyography results revealed that for the gluteus maximus there was significantly greater EMG activity during the NC condition vs. the CH condition. For the erector spinae, EMG activity was greater at the bottom than the top ROM (p ≤ 0.05). Force plate results revealed that deadlifting at 85% 1RM with an accommodating chain resistance of approximately 20% results in a reduction in GRFs (p ≤ 0.05) and no change in RFD (p > 0.05). Collectively, these results suggest that the use of chain resistance during deadlifting can alter muscle activation and force characteristics of the lift.

Endocrine response to acute resistance exercise in obese versus lean physically active men.

PURPOSE: Resistance exercise induces a host of endocrine responses that potentiate its effects on body composition and metabolism. Excess adiposity negatively affects some hormonal responses to exercise in sedentary men. This study compared the resistance exercise (RE)-associated growth hormone (GH), insulin-like growth factor-1 (IGF-1), and testosterone responses in lean vs. obese physically active men. METHODS: Ten healthy physically active obese males (body fat  % 36.2 ± 4.03, age 24.6 ± 3.7 years, mass 104.5 ± 15.5 kg, height 178.8 ± 6.0 cm) were compared to ten lean counterparts (body fat  % 12.7 ± 2.9, age 24.6 ± 3.7 years, mass 77.1 ± 6.4 kg, height 177.2 ± 4.8 cm). The muscular endurance RE protocol consisted of six sets of ten repetitions per leg of stepping onto an elevated platform (20 % of participant's height) while wearing a weighted-vest (50 % of participant's lean mass). Pre-, immediately post-exercise (IP), and three more blood samples were collected during the one-hour recovery. RESULTS: When accounting for baseline differences there were no group by time interactions for GH (p = 0.33); or LH (p = 0.52). Lean presented a trend towards significance for higher IGF-1 IP (p = 0.08) than obese. Testosterone IP was similar in obese and lean, but lower in obese than lean at 30 min into recovery (p < 0.01). AUC were lower in obese than lean for all hormones (p < 0.05 for all). CONCLUSION: These findings suggest that excess adiposity does not appear to negatively affect the immediate GH and T responses to RE in active males; but possibly negatively affects IGF-1. However, the baseline and integrated concentrations during recovery appear negatively affected by excess adiposity.

Bench Press Upper-Body Muscle Activation Between Stable and Unstable Loads.

The bench press is one of the most commonly used upper-body exercises in training and is performed with many different variations, including unstable loads (ULs). Although there is much research on use of an unstable surface, there is little to none on the use of an UL. The purpose of this study was to investigate muscle activation during the bench press while using a stable load (SL) vs. UL. Twenty resistance-trained men (age = 24.1 ± 2 years; ht = 177.5 ± 5.8 cm; mass = 88.7 ± 13.7 kg) completed 2 experimental conditions (SL and UL) at 2 different intensities (60 and 80% one repetition maximum). Unstable load was achieved by hanging 16 kg kettlebells by elastic bands from the end of the bar. All trial lifts were set to a 2-second cadence with a slight pause at the bottom. Subjects had electrodes attached to 5 muscles (pectoralis major, anterior deltoid, medial deltoid, triceps brachii, and latissimus dorsi) and performed 3 isometric bench press trials to normalize electromyographic data. All 5 muscles demonstrated significantly greater activation at 80% compared with 60% load and during concentric compared with eccentric actions. These results suggest that upper body muscle activation is not different in the bench press between UL and SL. Therefore, coaches should use their preference when designing training programs.

Acute effects of caffeine on strength and muscle activation of the elbow flexors.

The purpose of this study was to examine the effects of caffeine on strength and muscle activation of the elbow flexors. Thirteen recreationally active male volunteers (mean ± SD, age: 21.38 ± 1.26 years) came to the laboratory 4 times. Visit 1 served as a familiarization visit. During visits 2 through 4, subjects ingested a randomly assigned drink, with or without caffeine (0, 5, or 10 mg·kg of body mass), and performed 3 maximal isometric muscle actions of the elbow flexors 60 minutes after ingestion. Maximal strength and rate of torque development (RTD) were recorded. Electromyographic (EMG) and mechanomyographic (MMG) amplitude and frequency, and electromechanical delay (EMD), and phonomechanical delay (PMD) were measured from the biceps brachii. The results indicated that the ingestion of 0 (placebo), 5, or 10 mg·kg of body mass of caffeine did not significantly influence (p > 0.05) peak torque, RTD, normalized EMG amplitude or frequency, normalized MMG amplitude, or EMD and PMD. Normalized MMG frequency was significantly lower (p ≤ 0.05) following ingestion of 5 mg·kg of body mass of caffeine compared with the placebo trial. This was most likely an isolated finding because MMG frequency was the only variable to have a significant difference across all trials. The results suggested that ingestion of either 5 or 10 mg·kg of body mass of caffeine does not provide an ergogenic effect for the elbow flexors during isometric muscle actions.