Sex-related differences in motor unit behavior are influenced by myosin heavy chain during high- but not moderate-intensity contractions.

AIMS: Motor unit recruitment and firing rate patterns of the vastus lateralis (VL) have not been compared between sexes during moderate- and high-intensity contraction intensities. Additionally, the influence of fiber composition on potential sex-related differences remains unquantified. METHODS: Eleven males and 11 females performed 40% and 70% maximal voluntary contractions (MVCs). Surface electromyographic (EMG) signals recorded from the VL were decomposed. Recruitment thresholds (RTs), MU action potential amplitudes (MUAPAMP ), initial firing rates (IFRs), mean firing rates (MFRs), and normalized EMG amplitude (N-EMGRMS ) at steady torque were analyzed. Y-intercepts and slopes were calculated for MUAPAMP , IFR, and MFR versus RT relationships. Type I myosin heavy chain isoform (MHC) was determined with muscle biopsies. RESULTS: There were no sex-related differences in MU characteristics at 40% MVC. At 70% MVC, males exhibited greater slopes (p = 0.002) for the MUAPAMP , whereas females displayed greater slopes (p = 0.001-0.007) for the IFR and MFR versus RT relationships. N-EMGRMS at 70% MVC was greater for females (p < 0.001). Type I %MHC was greater for females (p = 0.006), and was correlated (p = 0.018-0.031) with the slopes for the MUAPAMP , IFR, and MFR versus RT relationships at 70% MVC (r = -0.599-0.585). CONCLUSION: Both sexes exhibited an inverse relationship between MU firing rates and recruitment thresholds. However, the sex-related differences in MU recruitment and firing rate patterns and N-EMGRMS at 70% MVC were likely due to greater type I% MHC and smaller twitch forces of the higher threshold MUs for the females. Evidence is provided that muscle fiber composition may explain divergent MU behavior between sexes.

Myofiber hypertrophy adaptations following 6 weeks of low-load resistance training with blood flow restriction in untrained males and females.

The effects of low-load resistance training with blood flow restriction (BFR) on hypertrophy of type I/II myofibers remains unclear, especially in females. The purpose of the present study is to examine changes in type I/II myofiber cross-sectional area (fCSA) and muscle CSA (mCSA) of the vastus lateralis (VL) from before (Pre) to after (Post) 6 wk of high-load resistance training (HL; n = 15, 8 females) and low-load resistance training with BFR (n = 16, 8 females). Mixed-effects models were used to analyze fCSA with group (HL, BFR), sex (M, F), fiber type (I, II), and time (Pre, Post) included as factors. mCSA increased from pre- to posttraining (P < 0.001, d = 0.91) and was greater in males compared with females (P < 0.001, d = 2.26). Type II fCSA increased pre- to post-HL (P < 0.05, d = 0.46) and was greater in males compared with females (P < 0.05, d = 0.78). There were no significant increases in fCSA pre- to post-BFR for either fiber type or sex. Cohen's d, however, revealed moderate effect sizes in type I and II fCSA for males (d = 0.59 and 0.67), although this did not hold true for females (d = 0.29 and 0.34). Conversely, the increase in type II fCSA was greater for females than for males after HL. In conclusion, low-load resistance training with BFR may not promote myofiber hypertrophy to the level of HL resistance training, and similar responses were generally observed for males and females. In contrast, comparable effect sizes for mCSA and 1-repetition maximum (1RM) between groups suggest that BFR could play a role in a resistance training program.NEW & NOTEWORTHY This is the first study, to our knowledge, to examine myofiber hypertrophy from low-load resistance training with blood flow restriction (BFR) in females. Although this type of training did not result in myofiber hypertrophy, there were comparable increases in muscle cross-sectional area compared with high-load resistance training. These findings possibly highlight that males and females respond in a similar manner to high-load resistance training and low-load resistance training with BFR.

A noninvasive test for estimating myosin heavy chain of the vastus lateralis in females with mechanomyography.

This study examined relationships between percent myosin heavy chain (%MHC) expression and mechanomyographic amplitude (MMGRMS). Fifteen females (age ± SD=21.3 ± 5.3 yrs) completed isometric trapezoidal contractions at 30% and 70% maximal voluntary contraction (MVC). MMG was recorded from the vastus lateralis (VL). Participants gave a muscle biopsy of the VL post-testing. MMGRMS-torque relationships during the linearly varying segments were log-transformed and linear regressions were applied to calculate b terms (slopes). For the steady torque segment, MMGRMS was averaged. Correlations were performed for type I%MHC with the MMG variables. Multiple regression was utilized to examine prediction equations for type I%MHC. Type I%MHC was significantly correlated with the b terms during the increasing segment of the 70% MVC (p = 0.003; r = -0.718), and MMGRMS during steady torque at 30% (p = 0.008; r = -0.652) and 70% MVC (p = 0.040; r = -0.535). Type I%MHC reduced the linearity of the MMGRMS-torque relationship during the high-intensity linearly increasing segment, and MMGRMS at a low- and high-intensity steady torque. A combination of MMG variables estimated type I%MHC expression with 81.2% accuracy. MMG recorded during a low- and high-intensity isometric trapezoidal contraction may offer a simple, noninvasive test for estimating type I%MHC expression of the VL in sedentary females.

Similar Responses in the Akt/Protein Kinase B Signaling Pathway Following Different Lower-Body Exercise Volumes in Recreationally Active Men.

ABSTRACT: Pearson, JR, Moodie, N, Stout, KW, Hawkins, WC, Matuszek, M, Graham, ZA, Siedlik, JA, Vardiman, JP, and Gallagher, PM. Similar responses in the Akt/protein kinase B (PKB) signaling pathway after different lower-body exercise volumes in recreationally active men. J Strength Cond Res 37(5): 1034-1041, 2023-This project examined the differences between a single set (SS) compared to multiple sets (MS) of resistance exercise on the Akt/protein kinase B (PKB) signaling pathway, the expression of insulin-like growth factor-1 ( IGF-1 ), and the receptor for IGF -1 ( IGF-1R ) to better understand the types of resistance training protocols that are most beneficial in stimulating the muscle hypertrophic response. Sixteen healthy men were randomly selected into 2 groups of 8. Subjects in each group received 3 biopsies: (a) before exercise, (b) 15 minutes postexercise, and (c) 180 minutes postexercise. Subjects in the SS group performed 1 set of leg press to failure at 80% of their predetermined 1 repetition maximum (1RM). Subjects in the MS group performed 2 sets of 10 repetitions and 1 set to failure at 80% of their predetermined 1RM, with 3 minutes of rest between each set. Our results indicated no group × time interactions in the concentration of Akt signaling proteins. Furthermore, there were no group × time interactions in IGF-1 or IGF-1R expression. However, phosphorylated 4E-binding protein 1 levels increased 150% from pre to 180 minutes post ( p = 0.005). In addition, there was a significantly greater increase in IGF-1R expression in the SS group compared with the MS group (7.99 ± 10.07 vs. 4.41 ± 6.28; p = 0.026). Collectively, we found that a SS of resistance training evokes a similar acute Akt/PKB pathway response as MS in recreationally active men.

Effects of continuous cycling training on motor unit firing rates, input excitation, and myosin heavy chain of the vastus lateralis in sedentary females.

This study examined the effects of continuous endurance training on motor unit (MU) mean firing rates (MFR), percent myosin heavy chain (%MHC) isoforms, and muscle cross-sectional area (mCSA) of the vastus lateralis (VL). Twelve females completed 5-weeks of continuous cycling-training (CYC), while 8 females were controls (CON). Participants performed maximal voluntary contractions (MVCs) and 40% MVCs of the knee extensors before (PRE) and after the 5-week treatment period at the same absolute pre-treatment submaximal torque (POSTABS) and relative to post-treatment MVCs (POSTREL). Surface electromyographic (EMG) signals were decomposed with the Precision Decomposition III algorithm. MU firing times and waveforms were validated with reconstruct-and-test and spike trigger average procedures. MFRs at steady torque, recruitment thresholds (RT), and normalized EMG amplitude (N-EMGRMS) were analyzed. Y-intercepts and slopes were calculated for the MFR vs. RT relationships. MHC isoforms and mCSA were determined with muscle biopsies and ultrasonography. CYC decreased MVCs and type IIX %MHC isoform without changes in mCSA. The slopes for the MFR vs. RT relationships decreased for CYC during POSTREL and POSTABS while N-EMGRMS increased for POSTABS with no differences between PRE and POSTREL. Type I %MHC isoform was correlated with the slope for the MFR vs. RT relationship during POSTABS and POSTREL for CYC. This study provides evidence that decreases in the MFRs of higher threshold MUs post-CYC is likely a function of changes in input excitation (POSTABS) and the firing frequency-excitation relationships (POSTREL). Evidence is provided that MHC isoforms influence the firing rate scheme of the muscle following short-term training.

Change in measures of moral function following acute bouts of Marine Corps Martial Arts Training.

The Marine Corps Martial Arts Program (MCMAP) was developed to prepare Marines for complex battlefield situations that include hand-to-hand combat and ethical decision making. The objective of this study was to quantify changes in ethical decision-making following MCMAP training. Fifty-five, active duty, newly enlisted U.S. Marines (Males: n = 37; age = 19 ± 1 years; height = 176 ± 7 cm; mass = 74 ± 7 kg; Females: n = 18; age = 20 ± 2 years; height = 164 ± 6 cm; mass = 61 ± 6 kg) volunteered for this investigation and were assessed three times over 6 weeks, with 3 weeks between each visit, using serial blood samples for cortisol, norepinephrine, and epinephrine collected before training and during recovery [Immediate Post (IP), 15, 30, 45 and 60 min]. The Moral Functioning Continuum was used to quantify moral function before training, IP, 30, and 60 min post. Moral intention exhibited an acute response to training with significantly impaired decision making immediately post training. Moreover, both moral intention and moral judgement worsened over the visits suggesting a chronic impairment related to time in training suggesting a functional change in ethical decision-making following acute bouts of MCMAP.

Effects of Transspinal Direct Current Stimulation on Cycling Perception of Effort and Time to Exhaustion.

ABSTRACT: Ciccone, AB, Fry, AC, Emerson, DM, Gallagher, PM, Herda, TJ, and Weir, JP. Effects of transspinal direct current stimulation on cycling perception of effort and time to exhaustion. J Strength Cond Res 35(2): 347-352, 2021-In the past decade, researchers have investigated the efficacy of transspinal direct current stimulation (tsDCS) on the central nervous system and afferent neuron function in humans. Recently, data have suggested it may be possible for such tsDCS-induced changes in neuromuscular function to enhance performance. This study used noninvasive thoracic spine tsDCS to determine if cycling performance and perception of effort could be modulated by tsDCS. In 3 different stimulation conditions, anodal, cathodal, and sham, subjects cycled at 80% of their maximal aerobic capacity until exhaustion and reported their rating of perceived exertion (RPE) every minute. From this period, we compared the RPE responses over the first 3 minutes and time to exhaustion. There was no significant difference in time to exhaustion between anodal (408 ± 121 seconds), cathodal (413 ± 168 seconds), and sham (440 ± 189 seconds) conditions (p = 0.58). There was no significant difference in RPE from minutes 1-3 (collapsed across time) between anodal (12.9 ± 2.4 arbitrary units (AUs)), cathodal (13.3 ± 2.2 AUs), and sham (12.9 ± 2.1 AUs) conditions (p = 0.51). These data suggest tsDCS condition did not influence cycling performance or perception of effort during high-intensity cycling. Therefore, thoracic spine and lower abdominal montage delivering a current density of 0.071 mA·cm-2 for 20 minutes likely does not substantially improve high-intensity cycling work capacity. Therefore, more research is needed to investigate the efficacy of tsDCS and which stimulation methods may and may not enhance human performance.

Skeletal Muscle Composition and Glucose Levels in Children Who Are Overweight and Obese.

BACKGROUND: Skeletal muscle is overlooked in the realm of insulin resistance in children who are overweight and obese despite the fact that it accounts for the most glucose disposal. OBJECTIVES: Therefore, this study examined fasted glucose levels and muscle cross-sectional area and echo intensity (EI) via ultrasound images of the first dorsal interosseous, vastus lateralis, and rectus femoris in children who are normal weight and overweight and obese aged 8-10 years. METHODS: In total, 13 males (age = 9.0 [0.7] y) and 7 females (age = 9.0 [0.8] y) volunteered for this study. Independent samples t tests and effect sizes (ESs) were used to examine potential differences in skeletal muscle composition and glucose concentrations. RESULTS: There were no significant differences between groups for glucose concentration (P = .07, ES = 0.86); however, the children who were overweight and obese had significantly greater EI (P < .01, ES = 0.98-1.63) for the first dorsal interosseous, vastus lateralis, and rectus femoris and lower cross-sectional area when normalized to EI when collapsed across muscles (P < .04, ES = 0.92). Glucose concentrations correlated with EI and cross-sectional area/EI for the vastus lateralis (r = .514 to -.593) and rectus femoris (r = .551 to -.513), but not the first dorsal interosseous. DISCUSSION: There is evidence that adiposity-related pathways leading to insulin resistance and skeletal muscle degradation are active in young children who are overweight and obese.

Muscular strength and power are correlated with motor unit action potential amplitudes, but not myosin heavy chain isoforms in sedentary males and females.

It remains unclear if the sizes of higher-threshold motor units (MU) are associated with muscular strength and power. Therefore, the purpose of this study was to examine sex-related differences in muscle cross-sectional area (mCSA), percent myosin heavy chain (%MHC) isoform expression, and the MU action potential amplitudes (MUAPAMPS)-recruitment threshold (RT) relationships of the vastus lateralis and isometric peak torque, isokinetic peak torque and mean power at 1.05 rad·s-1 of the leg extensors. Surface electromyographic decomposition techniques were used to quantify MUAPAMPS recorded during isometric muscle actions at 70% of maximal voluntary contractions and regressed against RTs with the slopes calculated. Ultrasound images were used to measure mCSA. Males had greater slopes from the MUAPAMP-RT relationship than the females (P < 0.05). The greater slopes likely reflected larger higher-threshold MUs for the males. The mCSAs and slopes from the relationships were strongly correlated with isometric and isokinetic peak torque and isokinetic mean power (r = 0.78-0.82), however, type I %MHC isoform was only moderately correlated with isometric peak torque (r = -0.54). The results indicated that sex-related differences in muscular strength and power were associated more so with the sizes of the higher-threshold MUs (slopes) and mCSA than MHC isoforms. The amount of cross-bridge activity within muscle fibers that comprise higher-threshold MUs may be the primary contributor to muscular strength and power rather than the contractile properties of the muscle.

Transcranial Direct Current Stimulation of the Temporal Lobe Does Not Affect High-Intensity Work Capacity.

Ciccone, AB, Deckert, JA, Schlabs, CR, Tilden, MJ, Herda, TJ, Gallagher, PM, and Weir, JP. Transcranial direct current stimulation of the temporal lobe does not affect high-intensity work capacity. J Strength Cond Res 33(8): 2074-2086, 2019-Stimulation of the left insular cortex may affect heart rate variability (HRV) and exercise effort perception. These studies investigated the effects transcranial direct current stimulation (tDCS) and electrode orientation on HRV and repeated maximal knee extensions. In study 1, after sham stimulation, anodal left temporal lobe stimulation, or anodal right temporal lobe stimulation, 10 male and 10 female subjects (age = 21.0 ± 1.5 years) completed 50 maximum isokinetic extensions at 180°·s. There was a significant effect of stimulation condition on HRV for only 1 (SD2; p = 0.037; η = 0.159) of 5 HRV metrics. There was no significant effect on isokinetic fatigue percent or isokinetic work (all p ≥ 0.278; all η ≤.065). It has been proposed that placing the cathode electrode on the shoulder may differentially affect tDCS. Therefore, in study 2, the effects of electrode orientation on tDCS-induced changes in HRV was assessed in 10 healthy females and 8 healthy males (21.6 ± 2.5 years) who completed cephalic, extracephalic, and sham trials. In the cephalic montage, the anode was placed over the left temporal lobe and the cathode was placed over right prefrontal cortex. In the extracephalic montage, the cathode was placed on the shoulder on the same side of the body as the anode. Neither cephalic nor extracephalic montages affected HRV (all p ≥ 0.152; all η ≤.105). These data suggest that anodal tDCS of the insular cortex has little effect on HRV, and does not improve high-intensity exercise performance in the current population. Therefore, anodal tDCS applied over the left temporal lobe is not recommended for high-intensity performance enhancement.

Effect of Three Different Maximal Concentric Velocity Squat Protocols on MAPK Phosphorylation and Endocrine Responses.

Kudrna, RA, Fry, AC, Nicoll, JX, Gallagher, PM, and Prewitt, MR. Effect of three different maximal concentric velocity squat protocols on MAPK phosphorylation and endocrine responses. J Strength Cond Res 33(6): 1693-1703, 2019-The purpose of this study was to determine the effect of 3 different back squat protocols on intracellular signaling, endocrine responses, and power fatigue. Nine recreationally trained men (X ± SD; age: 21.4 ± 0.6 years; height: 177.8 ± 5.1 cm; body mass: 78.7 ± 9.7 kg), completed 3 maximal concentric velocity squat protocols in a randomized order. Testing protocols consisted of 5 sets of 10 repetitions at 30% of 1 repetition maximum (1RM); 5 sets of 5 repetitions at 70% of 1RM; and 5 sets of 3 repetitions at 90% of 1RM. Average system power for each set was obtained using a tethered external dynamometer. Pre-exercise and postexercise blood draws were analyzed for lactate, testosterone, human growth hormone (hGH), and cortisol. Muscle biopsies assessed pre-exercise and postexercise extracellular signal-regulated kinase 1/2 (ERK1/2) and p38 phosphorylation using western blotting. Cortisol, hGH, and lactate increased after exercise (p ≤ 0.05), but did not differ between protocols (p > 0.05). Testosterone was unaltered (p > 0.05). Average power was lower for the 90% protocol than for the 30% protocol across all sets (p < 0.01). Average power was lower after the fourth and fifth set compared with the first and second set in the 90% protocol only (p ≤ 0.05). The ratio of phosphorylated-to-total ERK1/2 was higher postexercise after 90% protocol only (p ≤ 0.05). The ratio of phosphorylated-to-total p38 was unaltered after exercise (p > 0.05). Resistance load seems to affect power fatigue across the 5 sets of resistance exercise. This study found modest changes in ERK1/2 and no changes in p38 phosphorylation after maximal concentric velocity squats. Exercise volume, modality, and training status of subjects may account for these findings.

T cell activation and proliferation following acute exercise in human subjects is altered by storage conditions and mitogen selection.

Recent work investigating exercise induced changes in immunocompetence suggests that some of the ambiguity in the literature is resultant from different cell isolation protocols and mitogen selection. To understand this effect, we compared post-exercise measures of T cell activation and proliferation using two different stimulation methods (costimulation through CD28 or stimulation with phytohaemagglutinin [PHA]). Further, we investigated whether exercise induced changes are maintained when T cell isolation from whole blood is delayed overnight in either a room temperature or chilled (4°C) environment. As expected, an increased proliferation response was observed post-exercise in T cells isolated from whole blood of previously trained individuals immediately after blood collection. Also, cells stimulated with PHA after resting overnight in whole blood were not adversely impacted by the storage conditions. In contrast, allowing cells to rest overnight in whole blood prior to stimulation through CD28, lessened the proliferation observed by cells following exercise rendering both the room temperature and chilled samples closer to the results seen in the control condition. Changes in early markers of activation (CD25), followed a similar pattern, with activation in PHA stimulated cells remaining fairly robust after overnight storage; whereas cell activation following stimulation through CD3+CD28 was disproportionately decreased by the influence of overnight storage. These findings indicate that decisions regarding cell stimulation methods need to be paired with the timeline for T cell isolation from whole blood. These considerations will be especially important for field based studies of immunocompetence where there is a delay in getting whole blood samples to a lab for processing as well as clinical applications where a failure to isolate T cells in a timely manner may result in loss of the response of interest.

Influence of the contractile properties of muscle on motor unit firing rates during a moderate-intensity contraction in vivo.

It is suggested that firing rate characteristics of motor units (MUs) are influenced by the physical properties of the muscle. However, no study has correlated MU firing rates at recruitment, targeted force, or derecruitment with the contractile properties of the muscle in vivo. Twelve participants (age = 20.67 ± 2.35 yr) performed a 40% isometric maximal voluntary contraction of the leg extensors that included linearly increasing, steady force, and decreasing segments. Muscle biopsies were collected with myosin heavy chain (MHC) content quantified, and surface electromyography (EMG) was recorded from the vastus lateralis. The EMG signal was decomposed into the firing events of single MUs. Slopes and y-intercepts were calculated for 1) firing rates at recruitment vs. recruitment threshold, 2) mean firing rates at steady force vs. recruitment threshold, and 3) firing rates at derecruitment vs. derecruitment threshold relationships for each subject. Correlations among type I %MHC isoform content and the slopes and y-intercepts from the three relationships were examined. Type I %MHC isoform content was correlated with MU firing rates at recruitment (y-intercepts: r = -0.577; slopes: r = 0.741) and targeted force (slopes: r = 0.853) vs. recruitment threshold and MU firing rates at derecruitment (y-intercept: r = -0.597; slopes: r = 0.701) vs. derecruitment threshold relationships. However, the majority of the individual MU firing rates vs. recruitment and derecruitment relationships were not significant (P > 0.05) and, thus, revealed no systematic pattern. In contrast, MU firing rates during the steady force demonstrated a systematic pattern with higher firing rates for the lower- than higher-threshold MUs and were correlated with the physical properties of MUs in vivo.

The influence of myosin heavy chain isoform content on mechanical behavior of the vastus lateralis in vivo.

This study examined correlations between type I percent myosin heavy chain isoform content (%MHC) and mechanomyographic amplitude (MMGRMS) during isometric muscle actions. Fifteen (age=21.63±2.39) participants performed 40% and 70% maximal voluntary contractions (MVC) of the leg extensors that included increasing, steady force, and decreasing segments. Muscle biopsies were collected and MMG was recorded from the vastus lateralis. Linear regressions were fit to the natural-log transformed MMGRMS-force relationships (increasing and decreasing segments) and MMGRMS was selected at the targeted force level during the steady force segment. Correlations were calculated among type I%MHC and the b (slopes) terms from the MMGRMS-force relationships and MMGRMS at the targeted force. For the 40% MVC, correlations were significant (P<0.02) between type I%MHC and the b terms from the increasing (r=-0.804) and decreasing (r=-0.568) segments, and MMGRMS from the steady force segment (r=-0.606). Type I%MHC was only correlated with MMGRMS during the steady force segment (P=0.044, r=-0.525) during the 70% MVC. Higher type I%MHC reduced acceleration in MMGRMS (b terms) during the 40% MVC and the amplitude during the steady force segments. The surface MMG signal recorded during a moderate intensity contraction provided insight on the contractile properties of the VL in vivo.

Acute bouts of exercise induce a suppressive effect on lymphocyte proliferation in human subjects: A meta-analysis.

OBJECTIVE: Lymphocyte proliferative responses are commonly used to assess immune function in clinical settings, yet it is unclear how proliferative capacity is altered by exercise. This analysis aims to quantitatively assess the proliferative response of lymphocytes following an acute bout of exercise. METHODS: Electronic databases were searched for articles containing the keywords "exercise" OR "acute" OR "aerobic" OR "resistance training" OR "immune function" AND "proliferation" AND "lymphocyte." Initial results yielded 517 articles of which 117 were reviewed in full. Twenty-four articles met the inclusion criteria. Calculated standardized mean difference (SMD) and corresponding standard errors (SE) were integrated using random-effect models. RESULTS: Analyses uncovered evidence for suppression of proliferative capacity following acute exercise in general (SMD=-0.18, 95% CI: -0.21, -0.16) with long duration, high intensity exercise exhibiting a moderate suppressive effect (SMD=-0.55, 95% CI: -0.86, -0.24). Discordant proliferative responses for long duration, high intensity exercise in competitive versus non-competitive settings were identified with enhanced proliferation (SMD=0.46, 95% CI: 0.03, 0.89) observed following competitive events and a large suppressive effect detected for similar activities outside of a competitive environment (SMD: -1.28, 95% CI: -1.61, -0.96) (p=0.02). CONCLUSION: Evidence suggests lymphocyte proliferation is suppressed following acute bouts of exercise, with exercise lasting longer than one hour having a greater magnitude of effect regardless of exercise intensity. Variations in observed effect sizes across intensity, duration, and competitive environment further highlight our need to acknowledge the impact of study designs in advancing our understanding of exercise immunology.

Immunoendocrine alterations following Marine Corps Martial Arts training are associated with changes in moral cognitive processes.

Combined physical and psychological stress events have been associated with exacerbated endocrine responses and increased alterations in immune cell trafficking when compared to exercise stress alone. Military training programs are rigorous in nature and often purposefully delivered in environments combining high levels of both physical and mental stress. The objective of this study was to assess physiological and cognitive changes following U.S. Marine Corps Martial Arts training. Seven active-duty, male Marines were observed during a typical Marine Corps Martial Arts training session. Immune parameters, including immunomodulatory cytokines, and hormone concentrations were determined from blood samples obtained at baseline, immediately post training (IP) and at 15min intervals post-training to 1h (R15, R30, R45, R60). Assessments of cognitive moral functioning (moral judgment and intent) were recorded at intervals during recovery. There were significant fluctuations in immunoendocrine parameters. Peak endocrine measures were observed within the IP-R15 time interval. Distributions of circulating immune cells were significantly altered with neutrophils and all lymphocyte subsets elevated at IP. IFN-γ and IL-17a exhibited small, non-significant, parallel increases over the recovery period. Moral functioning was informed by different social identities during the recovery resulting in changes in moral decision-making. These data demonstrate that the Marine Corps Martial Arts Program induces significant alterations in lymphocyte and leukocyte distributions, but does not shift the balance of Th1/Th2 cytokines or induce a systemic inflammatory response. The program does, however, induce alterations in moral decision-making ability associated with the observed endocrine responses, even suggesting a potential interaction between one's social identities and endocrine responses upon moral decision-making.

Focal adhesion kinase and its role in skeletal muscle.

Skeletal muscle has a remarkable ability to respond to different physical stresses. Loading muscle through exercise, either anaerobic or aerobic, can lead to increases in muscle size and function while, conversely, the absence of muscle loading stimulates rapid decreases in size and function. A principal mediator of this load-induced change is focal adhesion kinase (FAK), a downstream non-receptor tyrosine kinase that translates the cytoskeletal stress and strain signals transmitted across the cytoplasmic membrane by integrins to activate multiple anti-apoptotic and cell growth pathways. Changes in FAK expression and phosphorylation have been found to correlate to specific developmental states in myoblast differentiation, muscle fiber formation and muscle size in response to loading and unloading. With the capability to regulate costamere formation, hypertrophy and glucose metabolism, FAK is a molecule with diverse functions that are important in regulating muscle cell health.

Methods comparison: assessing agreement of physiological parameters obtained from exercise on two different cycle ergometers.

The purpose of this study was to determine the agreement of physiological parameters measured during exercise testing on 2 devices at established power outputs (POs). Ten trained male cyclists were recruited. The devices used for comparison were the Lode stationary bicycle ergometer (SBE) (Lode Excalibur) and the PowerTap Pro+ (BPT) (Saris Cycling Group) mobile ergometer. The physiological parameters recorded at established PO (50, 100, 150, 200, 250 W) were heart rate (HR), oxygen consumption ((Equation is included in full-text article.)), pulmonary ventilation (VE), blood lactate, and ratings of perceived exertion (RPE). Subjects were randomized once to the SBE and 3 times to a bicycle equipped with a BPT. After 15 minutes of unloaded pedaling, the trial began with 5 minutes of cycling at 50 W. Intensity increased by 50 W every 5 minutes up to 250 W. Physiological measures were recorded at each PO. Bland-Altman plots were constructed including computation of the ratio of half the range of limits of agreement and the mean of the pairwise means along with bivariate regression calculations for analysis of the linear association between device measurements. Moderate to good agreement was found for HR with agreement improving as PO increased. Comparisons of (Equation is included in full-text article.)found agreement increased as the PO increased. VE, RPE, and lactate did not consistently provide similar measures across trials. The level of agreement between HR and (Equation is included in full-text article.)when comparing the SBE and BPT suggests that the PowerTap Pro+ is a sufficient tool for estimating PO and associated physiological parameters in the field.

Changes in α7ß1 integrin signaling after eccentric exercise in heat-shocked rat soleus.

INTRODUCTION: α7ß1 integrin links the extracellular matrix to the focal adhesion (FA) in skeletal muscle and serves as a stabilizing and signal relayer. Heat shock (HS) induces expression of proteins that interact with the FA. METHODS: Male Wistar rats were assigned to 1 of 3 groups: control (CON); eccentric exercise (EE); or EE+HS (HS). Soleus muscle was analyzed at 2 h and 48 h post-exercise. RESULTS: The 120-kDa α7 integrin decreased in the EE and HS groups, and the 70-kDa peptide decreased in the EE group at 2 h post-exercise. Total expression of focal adhesion kinase (FAK) and RhoA were decreased in EE and HS at 2 h post-exercise. Expression of phosphorylated FAK(397) decreased in the EE group but not the HS group at 2 h post-exercise. CONCLUSIONS: Long-duration EE may cause alterations in the FA in rat soleus muscle through the α7 integrin subunit and FAK.