Limb immobilization is a commonly used therapeutic intervention during periods of recovery from injury. To improve rehabilitation outcomes, interventions that curtail the severe decrements in muscular size and strength that occur during immobilization are critically needed. The purpose of this study was to assess the effects of two distinct interventions during one week of knee-joint immobilization on muscular size, strength, and neuromuscular function. Thirty-nine healthy, college-aged adults (21 males and 18 females) participated in this study. Participants were randomized into one of four groups: immobilization only (n = 9) , immobilization + action observation/mental imagery (AOMI) (n = 10), immobilization + neuromuscular electrical stimulation (NMES) (n = 12), or a control group (n =8). The AOMI group performed daily video observation and mental imagery training of leg extensions. The NMES group performed twice daily sessions of vastus lateralis (VL) and rectus femoris (RF) stimulation at increasing intensities. Muscular size, muscular strength, and neuromuscular function were measured before and after the immobilization period. The results of multiple analyses of covariance (ANCOVAs) indicated that neither AOMI nor NMES significantly mitigated disuse-induced deficits. However, based on percent differences in outcomes between groups, AOMI may hold promise as an effective method of maintaining greater levels of strength during periods of immobilization, as ANCOVA adjusted posttest means indicated 10.7% greater MVC peak torque for the AOMI group versus the immobilization group, as well as 18.2% and 9.6% greater concentric isokinetic peak torque at 30°/s and 180°/s, respectively. Additionally, when examining within group changes, AOMI resulted in increased concentric isokinetic peak torque at 30°/s by 7.2%. Given the daily video/imagery content of the AOMI group, successful AOMI interventions are likely highly specific, and may be modulated by increased corticospinal excitability. These findings may have clinically significant implications for those undergoing periods of prescribed immobilization.

The purposes of this study were to determine the reliability of the bat swing (BS) and rotational medicine ball throw (RMBT) load-velocity profiling (LVP) methods and the relationships between LVP variables and batting performance in NCAA Division I softball players. Current NCAA Division I softball athletes participated in this study. Bat velocity was tracked with a swing sensor during the BS method. An inertial measurement unit (IMU) tracked forearm velocity during the BS and RMBT methods. Two-way intraclass correlation coefficients (ICC) were used for relative reliability and coefficient of variation (CV) was used for absolute reliability. For the BS method with the swing sensor, relationships between the multiple- and two-load models and between LVP variables and batting variables were examined using Pearson's correlation coefficients. During the RMBT method and BS method using the IMU, no LVP variables were reliable (ICC = 0.7; CV = 15%). For the BS method with the swing sensor, all bat loads and V0 had acceptable reliability using peak velocity (PV) and average peak velocity (PVavg) (ICC > 0.7; CV < 15%). All LVP variables were highly related between the multiple- and two-load models when utilizing PV and PVavg (r = 0.915-0.988; p < 0.01). There were significant relationships (r = 0.603-0.671; p < 0.05) between PV using the 0.99 kg bat load and slugging percentage and on-base plus slugging, and between V0 and doubles, runs batted in, and total bases. Neither the RMBT method nor the BS method using the IMU provided reliable LVP variables. All bat velocities were highly reliable during the BS method using the swing sensor, while only V0 provided acceptable reliability. Practitioners may utilize the two-load model when utilizing the BS method using the swing sensor, although further research is needed to examine the relationship between LVP variables and batting performance.

No description available.

The purpose of this study was to develop a regression equation to predict VO2max based on non-exercise (N-EX) data. All participants (N = 100), aged 18-65 years old, successfully completed a maximal graded exercise test (GXT) to assess VO2max (mean ± SD; 39.96 mL∙kg-¹∙min&sup-1; ± 9.54 mL∙kg-¹∙min-¹). The N-EX data collected just before the maximal GXT included the participant's age, gender, body mass index (BMI), perceived functional ability (PFA) to walk, jog, or run given distances, and current physical activity (PA-R) level. Multiple linear regression generated the following N-EX prediction equation (R = .93, SEE = 3.45 mL∙kg-¹∙min-¹, %SEE = 8.62): VO2max (mL∙kg-¹∙min-¹) = 48.0730 + (6.1779 x gender) - (0.2463 x age) - (0.6186 x BMI) + (0.7115 x PFA) + (0.6709 x PA-R). Cross validation using PRESS (predicted residual sum of squares) statistics revealed minimal shrinkage (Rp = .91 and SEEp = 3.63 mL∙kg-¹∙min-¹); thus, this model should yield acceptable accuracy when applied to an independent sample of adults (aged 18-65) with a similar cardiorespiratory fitness level. Based on standardized β-weights the PFA variable (0.41) was the most effective at predicting VO2max followed by age (-0.34), gender (0.33), BMI (-0.27), and PA-R (0.16). This study provides a N-EX regression model that yields relatively accurate results and is a convenient way to predict VO2max in adult men and women.

Background Professional Rugby Union is a popular international team sport and is known to have one of the highest reported incidences of injury and illness across sporting codes. The Super Rugby tournament is played annually between professional Rugby Union teams and is one of the most competitive sports tournaments in the world. The demanding nature of the tournament has been associated with high rates of injury and illness, but the relationship between training loads on injury and illness profiles are unclear. As a result, the Super Rugby tournament is a platform to further investigate injury, illness and training load patterns within Rugby Union. Epidemiological data on training loads, injury profiles and illness patterns assist the development of preventative measures. Aim The aim of this study was to assess the relationships between training loads, injury profiles and illness rates in elite South African rugby players competing in the 2017 Super Rugby tournament. Specific objectives (a) To determine the incidence of training and match injuries during pre-season training, and early and late competition during the 2017 Super Rugby tournament; (b) To determine the incidence of illness during pre-season training, and early and late competition during the 2017 Super Rugby tournament; (c) To determine the anatomical site, type, mechanism and time-loss of injuries sustained during preseason training, and early and late competition during the 2017 Super Rugby tournament; (d) To determine potential associations between internal and external training loads; and injury and illness, respectively. Methods A descriptive, observational, surveillance study design was conducted on the 2017 Super Rugby tournament. Thirty-nine adult participants were recruited from one South African team over a complete season, including preseason, early and late competition. Data were collected from the team medical personnel who routinely collected data on a daily basis. Training load data included squad size, training or match day, the duration of training or matches, and internal and external training load measures for training and matches. Injury data included the participants age, the injury counts, the type of injury, the main and specific anatomical location, and the mechanism and severity of injury. Illness data included illness counts, the bodily system affected, symptoms and cause of illness, the specific diagnosis and time-loss. Results The overall incidence of injury was 12.8 per 1000 player hours. The majority (48.8%) of injuries occurred in the early competition phase. The incidence of match injuries (241.0 per 1000 player hours) was significantly higher than training injuries (3.3 per 1000 player hours). The lower limb (62.5%) sustained the greatest proportion of injuries. Muscle or tendon injuries accounted for 64.9% of all injuries. The tackle accounted for 28.8% of all injuries and 37.5% of all injuries were of a ‘moderate' severity. The proportion of players that sustained a time-loss injury was 76.9% (n = 30) and 25.6% (n = 10) of players sustained a time-loss injury severe enough to prevent eight days or more of participation in training or matches. The overall incidence of illness was 1.8 per 1000 player days. The proportion of players that acquired an illness was 28.3% (n = 11). Acute respiratory tract infections (28.6%) was the most common specific A significant negative correlation between injury and internal training loads were detected in the preseason phase (r = -0.34, p = 0.03). There were no significant correlations between external training load and injury incidence. No significant correlations were observed between internal and external training loads and illness incidence. There were no significant odds ratios demonstrated between internal and external acute to chronic ratios, and injury and illness risk. Conclusion The incidence of match injuries in this study was significantly higher than previously reported incidence rates in the Super Rugby tournament. The profiles of match and training injuries, anatomical location, type, mechanism and severity of injuries are similar to previous studies. Illness rates were significantly lower than reported in previous studies. Internal training load and injury were significantly correlated in the preseason phase. Further studies are required to determine the relationship of training loads on injury and illness over consecutive seasons and in multiple teams. diagnosis. A large majority of illnesses (64.3%) did not result in time-loss.

Resistance exercise eliciting muscle damage results in an immune response, leading to increases in circulating cytokines, and immune cell mobilization. Classical monocytes respond to muscle damage, however, little is known about the intermediate or nonclassical monocyte response to resistance exercise. Moreover, the impact of polyphenol supplementation in conjunction with resistance exercise on the innate immune response is unknown. The purpose of this study was to examine the immune response following resistance exercise with (PPB) and without (PL) polyphenol supplementation. Thirty-nine untrained men were randomized into three groups: PPB (n=13, 21.8±2.5yrs, 171.2±5.5cm, 71.2±8.2kg), PL (n=15, 21.6±2.5yrs, 176.5±4.9cm, 84.0±15.7kg) or a control group (CON) (23.3±4.1yrs, 173.6±12.0cm, 77.8±15.6kg). Blood samples were obtained pre- (PRE), immediately- (IP), 1- (1H), 5- (5H), 24- (24H), 48- (48H) and 96- (96H) hours postexercise (PPB/PL). CON rested for one hour between PRE and IP blood draws. Changes in granulocyte and monocyte subset proportions and adhesion characteristics (CD11b) were assessed via flow cytometry, while plasma cytokine concentrations and markers of muscle damage were analyzed via multiplex and spectrophotometric assays, respectively. Creatine Kinase and myoglobin were elevated at each time point for PPB and PL (p < 0.050). Monocyte chemoattractant protein-1 was significantly elevated at IP in PPB (p = 0.005) and PL (p = 0.006) and significantly greater than CON at 5H (PPB: p < 0.001; PL: p = 0.006). Granulocyte proportions were elevated at 1H (p < 0.001), 5H (p < 0.001) and 24H (p = 0.005; p = 0.006) in PPB and PL, respectively. Classical monocyte proportions were lower in PPB (p = 0.008) and PL (p = 0.003) than CON at IP, and significantly greater than CON at 1H (PPB: p = 0.002; PL: p = 0.006). Nonclassical monocyte proportions were significantly greater in PPB (p = 0.020) and PL (p = 0.028) than CON at IP. Intermediate monocyte proportions were significantly greater in PPB (p = 0.034) and PL (p = 0.001) than CON at IP, and significantly lower than CON at 1H (PPB: p = 0.003; PL: p = 0.008). Intermediate monocyte proportions were also significantly greater in PPB than CON at 24H (p = 0.016) and 48H (p = 0.007). At PRE, CD11b expression was significantly lower in the PPB group than CON and PL for intermediate (p = 0.017; p = 0.045) and nonclassical (p < 0.001, p = 0.019) monocytes, respectively. When groups were combined, CD11b expression was significantly elevated from PRE at IP (p < 0.001) and 1H (p = 0.015) on granulocytes. CD11b expression on classical monocytes was significantly elevated compared to PRE at 1H (p < 0.001), 5H (p = 0.033) and 24H (p = 0.004) when groups were combined. CD11b expression on intermediate monocytes was significantly elevated compared to PRE at 1H (p < 0.001) when groups were combined. Intermediate and nonclassical monocyte proportions also showed significant positive correlations with markers of muscle damage (r = 0.361 to 0.775, p < 0.05). Results indicated that resistance exercise in novice lifters may elicit a selective mobilization of intermediate monocytes at 24h and 48H, and that muscle damage may be related to increases in intermediate and nonclassical monocytes. In addition, polyphenol supplementation appeared to suppress CD11b expression on monocytes to resistance exercise.

INTRODUCTION: The nuclear factor kappa B (NF-κβ) signaling cascade is responsible for mediating stress-activated catabolic effects of Tumor Necrosis Factor Alpha (TNF-α) downstream of the TNF receptor (TNFR1). NF-κβ transcription factor remains inhibited in the cytosol of the muscle and can be stimulated for translocation and transcription by a variety of external stimuli, most notably by pro-inflammatory cytokines and oxidative stress. Nevertheless, currently there is a gap in the literature with regard to the time course effect of NF-κβ signaling following acute resistance exercise in humans. PURPOSE: To observe the effects of an acute lower-body resistance exercise protocol and subsequent recovery on intramuscular NF- κβ signaling. METHODS: Twenty-eight untrained males were assigned to either a control (CON; n=11) or exercise group (EX; n=17) and completed a lower-body resistance exercise protocol consisting of the back squat, leg press, and leg extension exercises. Skeletal muscle microbiopsies were obtained from the vastus lateralis pre-exercise (PRE), 1-hour (1HR), 5-hour (5HR), and 48-hours (48HR) post-resistance exercise. Multiplex signaling assay kits (EMD Millipore, Billerica, MA, USA) were used to quantify the total protein (TNFR1, c-Myc) or phosphorylation status of proteins (IKKa/b, NF- κβ, IkB) specific to apoptotic signaling pathways using MAGPIX® (Luminex, Austin, TX, USA). Repeated measures ANOVA analysis was used to determine the effects of the exercise bout on intramuscular signaling at each timepoint. Additionally, change scores were analyzed by magnitude based inferences to determine a mechanistic interpretation. RESULTS: Repeated measures ANOVA indicated a trend for a two way interaction between the EX and CON Group (p=0.064). Magnitude based inferences revealed a "Very Likely" increase in total c-Myc from PRE-5H and a "Likely" increase in IkB phosphorylation from PRE-5H. CONCLUSION: Results indicate that c-Myc transcription factor and phosphorylation of IkB are elevated following acute intense resistance exercise in untrained males. These data suggest that NF- κβ signaling plays a role in ribosome biogenesis and skeletal muscle regeneration following resistance exercise in young untrained males.

The immune system has been implicated in recovery and muscle regeneration following exercise. In response to muscle damage, the immune system responds with an increase in circulating pro-inflammatory cytokines with the goal of recruiting leukocytes to the damaged area. Tumor Necrosis Factor-alpha (TNF-α), in particular, has been shown to be implicated in both muscle regeneration and muscle wasting. However, it remains unclear whether TNF-α is responsible for the age-related losses in muscle size and function. Also, due to the high clearance rate of TNF-α from circulation, analyzing the circulating levels of soluble TNF-α receptors 1 and 2 (STNFR1 and STNFR2) may provide a better indication of inflammatory events. Therefore, the purpose of this study was to compare changes in circulating levels of TNF-α, STNFR1, and STNFR2 following an acute muscle damaging intervention in young age (YA) and middle-aged (MA) males. Recreationally active young (YA; N=9, 21.8 ± 2.2 y, 179.5 ± 4.9 cm, 91.2 ± 12.2 kg, 21.8 ± 4.3% BF) and middle-aged (MA; N=10, 47.0 ± 4.4 y, 176.8 ± 7.6 cm; 96.0 ± 21.5 kg, 25.4 ± 5.3% BF) males completed an acute muscle damaging protocol (MDP). Blood samples were obtained at baseline (BL), immediately (IP), 30 minutes (30P), 60 minutes (60P), 120 minutes (120P), 24 hours (24H), and 48 hours (48H) post-MDP. Lower body performance was analyzed via isokinetic dynamometer at BL, IP, 120P, 24H, and 48H. No significant group x time interactions or main group effects were observed for TNF-α, STNFR1, STNFR2 or any marker of muscle damage. When collapsed across groups, plasma lactate was significantly elevated at IP (p < 0.001) and 30P (p = 0.003); serum myoglobin was increased at 30P (p = 0.002), 60P (p = 0.001), and 120P (p = 0.007); creatine kinase was elevated at 24H (p = 0.001) and 48H (p = 0.005). Plasma concentrations of TNF-α were unchanged following MDP. With both groups combined, serum STNFR1 was decreased at 30P (p = 0.001) and increased at 48H (p = 0.028). Serum STNFR2 was decreased at 30P (p = 0.008), 60P (p = 0.003), and 120P (p = 0.002). The results of this study indicate that the TNF-α and STNFRs response to exercise is similar between young and middle-aged males. Measuring STNFRs may be a more appropriate method of assessing the acute inflammatory response to muscle damage. In addition, an acute bout of exercise may attenuate ectodomain shedding of TNFR1 and TNFR2.

PURPOSE: The purpose of this study was to compare the effects of a high volume isokinetic intervention on lower body strength and inflammation, as well as markers of muscle damage in the subsequent 48 hours between younger and middle-aged men. METHODS: 19 healthy, recreationally trained men were randomly assigned to two groups, younger adults (YA: 21.8 ± 2.0 y; 90.7 ± 11.6 kg; 21.5 ± 4.1 % body fat), or middle-aged adults (MA: 47.0 ± 4.4 y; 96.0 ± 21.5; 24.8 ± 6.3 % body fat). Both groups reported to the human performance laboratory (HPL) on four separate occasions. On the first visit (D1), anthropometric assessment, as well as a familiarization session with the isokinetic dynamometer, was performed. A muscle damaging protocol (HVP) was performed on the second visit (D2) consisting of 8 sets of 10 repetitions at 60°·sec-1 on the isokinetic dynamometer. An assessment protocol (AP) was performed to assess performance decrements between the YA and MA groups. For this protocol, a maximal voluntary isometric contraction (MVIC) was performed, as well as 3 isokinetic kicks at 2 different speeds (240°·sec-1 and 60°·sec-1). For the MVIC, values for peak torque (PKT), average torque (AVGT), rate of torque development at 100 ms (RTD100), and 200 ms (RTD200) were recorded. For the isokinetic kicks at 240°·sec-1 (ISK240) and 60°·sec-1 (ISK60), values were also recorded for peak torque (PKT), average torque (AVGT), as well as peak power (PP), and average power (AVGP). The AP was performed before the HVP (BL), immediately after the HVP (IP), 120 minutes after the HVP (120P), as well as one (24H) and two (48H) days following the HVP. Blood draws were also taken at BL, IP, 24H, and 48H, as well as 30 minutes (30P), and 60 minutes (60P) following the HVP to assess circulating levels of creatine kinase (CK), myoglobin (Mb), c-reactive protein (CRP), and interleukin 6 (IL-6). Ultrasound assessment was also performed at BL and IP as well to assess changes in muscle morphology as a result of the intervention. Performance, blood, and ultrasound markers were analyzed using a repeated measures ANOVA to observe between group comparisons for all of the outcome variables. RESULTS: There were no group differences observed for isometric or isokinetic peak torque or average torque, nor were there differences in isokinetic peak power or average power between the two groups as a result of the intervention. There were, however, differences in the pattern for rate of torque development at 100 ms and 200 ms between the two groups. RTD 100 was decreased at IP and 48H in YA, with MA showing decreases at IP, but also 120P and 24H unlike YA. RTD200 was decreased at all time points in YA, while MA was decreased at IP, 24H, and 48H, but not 120P. For markers of muscle damage and inflammation, there were no differences in the response of Mb, CK, CRP, or IL-6 between groups. CONCLUSIONS: Age does not appear to be a driving factor in the inflammatory or muscle damage response from a high volume isokinetic intervention. Though changes in peak torque and average torque from a high volume isokinetic intervention do not seem to differ between younger and middle-aged adults, the rate of torque production at 100ms and 200ms is different between groups. This suggests that while recovery to average or maximal strength after an exercise bout may not be affected greatly by age, the rate of neuromuscular recovery from exercise may be primarily affected by other factors such as training status.

Suarez, DG, Carroll, KM, Slaton, JA, Rochau, KG, Davis, MW, and Stone, MH. Utility of a shortened isometric midthigh pull protocol for assessing rapid force production in athletes. J Strength Cond Res XX(X): 000-000, 2020-The purpose of this investigation was to determine the magnitude of difference, reliability, and relationship to performance of a shortened isometric midthigh pull (IMTP) protocol. Fourteen strength-trained men (age: 26.8 ± 5.0 years, height: 176.3 ± 6.9 cm, body mass: 86.8 ± 13.9 kg, and training age: 8.5 ± 6.9 years) performed 1-second (SHORT) and traditional (TRAD) IMTP protocols during consecutive weeks. Peak force (PF), instantaneous force (90 & 200 ms), rate of force development (RFD) (0-90 ms & 0-200 ms), and impulse (0-90 ms & 0-200 ms) from each protocol were collected. Paired samples t test and Hedge's g were calculated to determine the magnitude of difference in each variable between protocols. Within-session and between-session reliability was assessed with intraclass correlation coefficient, coefficient of variation, and 95% confidence intervals. Static jumps were performed to compare relationships of the IMTP variables from each protocol with jumping performance. There was no statistically significant (p > 0.05) difference in PF between the protocols (p = 0.345; g = -0.07). All early force-time variables were significantly higher in the SHORT protocol (p = <0.001-0.018; g = 0.38-0.79). The SHORT protocol resulted in more reliable RFD measures within-session. Correlations with jumping performance were mostly similar between protocols (r = 0.253-0.660). The SHORT IMTP protocol resulted in comparable PF values and considerably higher early force-time characteristics despite a restrained time to produce force and shorter rest. The SHORT protocol allows for an accurate assessment of rapid force-generating abilities while necessitating shorter collection periods than typical IMTP protocols.