Nicholas A. Coker

Influence of Skeletal Muscle Carnosine Content on Fatigue during Repeated Resistance Exercise in Recreationally Active Women

Carnosine is a naturally occurring intramuscular dipeptide that is thought to attenuate fatigue during high-intensity exercise. Carnosine content is influenced by various factors, including gender and diet. Despite research reporting that carnosine content is lower in women compared to men and lower in vegetarians compared to omnivores, no investigations have examined carnosine content in women based on dietary protein intake and its effect on muscle fatigue. Twenty recreationally active women were assigned to either a high (HI; n = 5), moderate (MOD; n = 10), or low (LO; n = 5) group based upon intramuscular carnosine content of the vastus lateralis. Each participant underwent two unilateral maximal voluntary isometric contractions (MVIC) of the knee extensors separated by an isokinetic exercise protocol consisting of five sets of 50 repeated maximal unilateral contractions. Magnitude-based inferences were used to analyze group differences. Percent decline in rate of force development and peak torque (PT) during the MVICs and changes in PT and mean torque during the muscle-fatiguing protocol were lower in HI compared to both MOD and LO. Additionally, absolute and relative dietary protein intake were greater in HI compared to MOD or LO. Results indicated that greater intramuscular carnosine content was reflective of greater dietary protein intake and that individuals with higher carnosine content displayed a greater attenuation of fatigue compared to those with lower carnosine.

β-Alanine Supplementation Elevates Intramuscular Carnosine Content and Attenuates Fatigue in Men and Women Similarly, but does not Change Muscle L-Histidine Content

β-Alanine (BA) supplementation results in elevated intramuscular carnosine content, enhancing buffering capacity during intense exercise. Although men have greater muscle carnosine content than women, elevations still appear to occur despite high baseline levels. Recent research has suggested that BA supplementation may also reduce muscle l-histidine. Thus, the purpose of this investigation was to compare 28 days of BA (6 g·d-1) supplementation in men and women on performance and muscle carnosine, l-histidine, and BA. We hypothesized that supplementation would result in similar elevations in carnosine and performance between sexes and decrease l-histidine. Twenty-six men and women were assigned either BA or placebo (PLA). At baseline, a trend toward greater carnosine (P = .069) was observed in men, and intramuscular BA content was significantly (P ≤ .05) greater in men. Statistical analysis was performed using magnitude-based inferences. Changes in muscle carnosine were likely and very likely greater after BA supplementation compared with PLA in men and women, respectively, but changes were unclear between sexes (mean sex difference: 2.50 ± 4.30 mmol·kg-1 ww). The attenuation of exercise fatigue was likely greater in BA compared with PLA, but the change was unclear between sexes (mean sex difference: 14.0 ± 39.0 Nm). Changes in muscle BA following supplementation was unclear in men, likely elevated in women, but unclear between sexes (mean sex difference: 0.03 ± 0.42 mmol·kg-1 ww). Changes in muscle l-histidine were unclear in men and women, and unclear between sexes (mean sex difference: 0.09 ± 0.13 mmol·kg-1 ww). In conclusion, BA supplementation increased muscle carnosine and attenuated fatigue in men and women similarly but did not reduce muscle l-histidine.

Comparison of sustained-release and rapid-release β-alanine formulations on changes in skeletal muscle carnosine and histidine content and isometric performance following a muscle-damaging protocol

Abstractβ-alanine supplementation increases muscle carnosine content and improves anaerobic exercise performance by enhancing intracellular buffering capacity. β-alanine ingestion in its traditional rapid-release formulation (RR) is associated with the symptoms of paresthesia. A sustained-release formulation (SR) of β-alanine has been shown to circumvent paresthesia and extend the period of supply to muscle for carnosine synthesis. The purpose of this investigation was to compare 28 days of SR and RR formulations of β-alanine (6xa0gxa0day−1) on changes in carnosine content of the vastus lateralis and muscle fatigue. Thirty-nine recreationally active men and women were assigned to one of the three groups: SR, RR, or placebo (PLA). Participants supplementing with SR and RR formulations increased muscle carnosine content by 50.1% (3.87xa0mmolxa0kg−1ww) and 37.9% (2.62xa0mmolxa0kg−1ww), respectively. The change in muscle carnosine content in participants consuming SR was significantly different (pu2009=u20090.010) from those consuming PLA, but no significant difference was noted between RR and PLA (pu2009=u20090.077). Although participants ingesting SR experienced a 16.4% greater increase in muscle carnosine than RR, fatigue during maximal voluntary isometric contractions was significantly attenuated in both SR and RR compared to PLA (pu2009=u20090.002 and 0.024, respectively). Symptoms of paresthesia were significantly more frequent in RR compared to SR, the latter of which did not differ from PLA. Results of this study demonstrated that only participants consuming the SR formulation experienced a significant increase in muscle carnosine. Differences in the muscle carnosine response between these formulations may have practical significance for athletic populations in which small changes may have important implications on performance.

Use of B-Mode Ultrasound as a Body Fat Estimate in Collegiate Football Players

Abstract Hyde, PN, Kendall, KL, Fairman, CM, Coker, NA, Yarbrough, ME, and Rossi, SJ. Utilization of B-mode ultrasound as a body fat estimate in collegiate football players. J Strength Cond Res 30(12): 3525–3530, 2016—The purpose of the present study was to validate a 7-site ultrasound imaging protocol to predict the percent body fat (%BF) in a division I football team. Body composition was estimated by ultrasound, 7-site skinfolds, and the 3-compartment-water (3C-W) model of Siri, using bioimpedance spectroscopy to estimate the total body water and air displacement plethysmography (using BODPOD) to determine the body density. Pearsons product-moment correlation analyses were run to determine correlations between &Sgr;Ultrasound and the criterion 3C-W, and between the &Sgr;Skinfold and &Sgr;Ultrasound. Strong positive correlations were observed between &Sgr;Skinfold and &Sgr;Ultrasound (r = 0.984; p < 0.001). Furthermore, a strong positive correlation was observed between &Sgr;Ultrasound and %BF from 3C-W (r = 0.878; p < 0.001). Based on the significant correlation analysis, a linear regression equation was developed to predict the %BF from &Sgr;Ultrasound, using %BF from the 3C-W model as the dependent variable: %BF = 6.194 + (0.096 × &Sgr;Ultrasound); standard error of the estimate (SEE) = 2.97%. Cross-validation analyses were performed using an independent sample of 29 players. The mean observed %BF from the 3C-W model and the mean predicted %BF were 18.32 ± 6.26% and 18.78 ± 6.22%, respectively. The constant error, SEE, and validity coefficient (r) were 0.87%, 2.64%, and 0.91%, respectively. The total error was 2.87%. The positive relationship between ultrasound measurements and the 3C-W model suggests that ultrasound imaging may be a practical alternative to predicting %BF in division I football players.

Predictors of competitive success of national-level powerlifters: a multilevel analysis

ABSTRACT Powerlifting is a sport consisting of the squat, bench press, and deadlift. The overall winner is determined using the Wilks formula to make comparisons across weight classes. To date, literature evaluating competitive performance in powerlifting is scarce. The purpose of this study was to evaluate the role of body mass and the number of successful attempts for each lift in determining competitive success. Individual and group level data were taken from the online USA Powerlifting Nationals database for the years 2015–2017. The analysis consisted of 2,532 individual cases taken from 2,021 individual male and female athletes nested within 17 weight classes. The number of successful attempts for squat (SQ), bench press (BP) and deadlift (DL), as well as body mass, were entered as individual level predictors. Multi-level analysis revealed that increased body mass within a weight class resulted in significantly increased Wilks points. Additionally, the number of successful squats and bench presses were significant, positive predictors of Wilks points. However, the number of successful deadlifts was not associated with greater competitive success. The results of this study suggest that competitive success in powerlifting may be aided by better competitive strategies regarding body mass manipulation and attempt selection.

Comparisons in the Recovery Response From Resistance Exercise Between Young and Middle-aged Men

Abstract Gordon, JA III, Hoffman, JR, Arroyo, E, Varanoske, AN, Coker, NA, Gepner, Y, Wells, AJ, Stout, JR, and Fukuda, DH. Comparisons in the recovery response from resistance exercise between young and middle-aged men. J Strength Cond Res 31(12): 3454–3462, 2017—The purpose of this study was to compare the effects of a bout of high-volume isokinetic resistance exercise protocol (HVP) on lower-body strength and markers of inflammation and muscle damage during recovery between young and middle-aged adult men. Nineteen recreationally trained men were classified as either a young adult (YA: 21.8 ± 2.0 years; 90.7 ± 11.6 kg) or a middle-aged adult (MA: 47.0 ± 4.4 years; 96.0 ± 21.5 kg) group. The HVP consisted of 8 sets of 10 repetitions, with 1 minute of rest between each set, performed on an isokinetic dynamometer at 60°·s−1. Maximal voluntary isometric contractions and isokinetic peak torque (PKT) and average torque (AVGT) (measured at 240° and 60°·s−1, respectively) were assessed at baseline (BL), immediately post (IP), 120 minutes, 24, and 48 hours after HVP. Blood was obtained at BL, IP, 30, 60, 120 minute, 24, and 48 hours after HVP to assess muscle damage and inflammation. All performance data were analyzed using repeated measures analysis of covariance, whereas all inflammatory and muscle damage markers were analyzed using a 2-way (time × group) repeated measures analysis of variance. Results revealed no between-group differences for PKT, AVGT, or rate of torque development at 200 ms (RTD200). No between-group differences in myoglobin, creatine kinase, C-reactive protein, or interleukin-6 were observed. Although BL differences in muscle performance were observed between YA and MA, no between-group differences were noted in performance recovery measures from high-volume isokinetic exercise in recreationally trained men. These results also indicate that the inflammatory and muscle damage response from high-volume isokinetic exercise is similar between recreationally trained, young, and middle-aged adult men.

Relationship Between Running Performance and Recovery-Stress State in Collegiate Soccer Players

Abstract Coker, NA, Wells, AJ, Ake, KM, Griffin, DL, Rossi, SJ, and McMillan, JL. Relationship between running performance and recovery-stress state in collegiate soccer players. J Strength Cond Res 31(8): 2131–2140, 2017—The purpose of this study was to evaluate the relationship between changes in running performance and the stress-recovery state in collegiate soccer players. Running performance was evaluated in 7 National Collegiate Athletic Association Division I male soccer players (179.39 ± 5.24 cm; 75.46 ± 5.98 kg; 20.37 ± 1.41 years) through global positioning systems over the course of 12 competitive games in a single season. The regular season was divided into 4 competitive blocks: B1 (n = 3), B2 (n = 3), B3 (n = 3), and B4 (n = 3). Total distance and distance covered while engaging in walking, jogging, low-speed running, high-speed running, sprinting, low-intensity running, and high-intensity running were assessed during each block. The Recovery-Stress Questionnaire (RESTQ) 52 Sport was administered twice during each block to evaluate measures of stress and recovery. Total distance was greater during B4 compared with B1 (p = 0.027). Jogging and low-speed running were greater during B4 compared with all other time points (ps ⩽ 0.05). Low-intensity running distance was greater during B4 compared with B1 (p = 0.034). Sport-specific recovery decreased significantly during B4 compared with B1 (p = 0.035). Correlational analysis indicated that high-velocity running was associated with increased stress, whereas low-velocity running was associated with greater recovery. However, changes in sport-specific recovery did not correlate with changes in running performance from B1 to B4. Results of this study indicate that running performance decreased across the season. Changes in running performance coincided with a decrease in sport-specific recovery. Practitioners may benefit from including the RESTQ as part of an assessment battery to monitor the stress/recovery state of athletes.

Tumor necrosis factor-alpha and soluble TNF-alpha receptor responses in young vs. middle-aged males following eccentric exercise.

Background Tumor necrosis factor‐alpha (TNF‐&agr;) has been shown to be implicated in both muscle regeneration and muscle wasting. However, it remains unclear whether TNF‐&agr; is responsible for the age‐related losses in muscle size and function. Also, due to the high clearance rate of TNF‐&agr; from circulation, analyzing the circulating levels of soluble TNF‐&agr; receptors 1 and 2 (STNFR1 and STNFR2) may provide a better indication of inflammatory events. The aim of this study was to examine changes in circulating concentrations of TNF‐&agr;, STNFR1, and STNFR2 following acute eccentric exercise in young (YA) and middle‐aged (MA) men. Methods and materials Nine YA (N = 9, 21.8 ± 2.2 y, 179.5 ± 4.9 cm, 91.2 ± 12.2 kg, 21.8 ± 4.3% body fat) and ten MA (N = 10, 47.0 ± 4.4 y, 176.8 ± 7.6 cm; 96.0 ± 21.5 kg, 25.4 ± 5.3% body fat) men completed an acute muscle damaging protocol (MDP). Blood samples were obtained at baseline (BL), immediately (IP), 30‐minute (30P), 60‐minute (60P), 120‐minute (120P), 24‐hour (24H), and 48‐hour (48H) post‐MDP. Lower body performance was assessed via isokinetic dynamometer at BL, IP, 120P, 24H, and 48H. Results YA displayed higher values of peak torque (p = 0.023) and mean torque (p = 0.036) at BL. No significant group differences were observed for markers of muscle damage or TNF‐&agr;. Plasma concentrations of TNF‐&agr; were unchanged following MDP. STNFR1 concentrations were significantly higher in the YA group compared to MA (p = 0.036). Significant time effects were observed for STNFR1 (p < 0.001) and STNFR2 (p = 0.001). With both groups combined, serum STNFR1 was decreased at 30P (p = 0.001), while STNFR2 was decreased at 30P (p = 0.008), 60P (p = 0.003), and 120P (p = 0.002) relative to BL. Conclusions The pro‐inflammatory response to muscle damage does not appear to decline at middle age when individuals are recreationally trained. However, young men showed significantly higher serum STNFR1 concentrations than middle age men. This may suggest that natural inhibitors of TNF‐&agr; decline as early as middle age. HighlightsAge‐related changes in circulating TNF‐&agr; and STNFR2 are not apparent at middle‐age but rather may only be seen in older age.The pro‐inflammatory response to muscle damage does not appear to decline at middle age in recreationally trained men.Young men showed significantly higher baseline serum concentrations of STNFR1 compared to middle aged men.The findings of this study suggest that natural inhibitors of TNF‐&agr; may decline as early as middle age.

Utilization of non-invasive measures to evaluate eccentric exercise damage in an untrained population

Background One of the most common modes of exercise among males is resistance training. The associated movements among the most common resistance training exercises completed include periods of both concentric and eccentric contraction. Previous research has demonstrated that repeated eccentric contractions of a muscle produce damaging results to the muscles involved. Invasive measures, such as blood draws and muscle biopsies have been utilized to assess skeletal muscle damage in individuals. However, the efficacy of the utilization of Creatine Kinase concentration as a marker of recovery has recently been called into question. Furthermore, biopsies and blood draws may not be applicable to identify muscle damage and recovery in an untrained population for the nutritional or strength and conditioning professional Methods Subjects (n= 19) volunteered to participate in this study and were untrained (resistance training) male college students between the ages of 18-30. Untrained criteria consisted of less than two years lower body resistance training. Prior to completion of the study participants completed a health history questionnaire. Participants were asked to refrain from physical activity for the duration of the study. The first day of testing included completion of a muscle soreness scale (DOMS), range of motion (ROM) of the dominant knee, swelling of the vastus lateralis (SWVL) via ultrasound (Terason T3200), Peak force measurement using an isokinetic dynamometer, a fatiguing exercise protocol on the dynamometer (a total of 50 eccentric contractions set at 120% of peak MVC force with an angular velocity of 60°/sec), followed immediately by post-test measurements of DOMS and peak force. The peak force measurement was determined using an isometric maximum voluntary contraction (MVC) of the quadriceps on the dynamometer with the knee joint held at 45°. The participants were then asked to return to the lab 24, 48 and 72 hours later. Each returning visit included a battery of tests comprising of measurements of DOMS, ROM, SWVL-Terascape, SWVL-Long, SWVL-Trans and peak force. Repeated measures ANOVAs (placebo vs. multi ingredient supplement) were used to analyze changes in peak power, intramuscular swelling, DOMS, and ROM. The alpha level was set at p≤ 0.05. Consent to publish the results was obtained from all participants. Results