Context: There has been recent speculation that the intrinsic muscles of the foot may play a larger role in lower extremity control and injury than previously believed. Multiple studies have shown that certain intrinsic muscles increase in size and strength after transitioning to minimalist shoe running, theoretically decreasing injury risk. There are currently no studies that examine the effect that training barefoot has in other athletic populations. Objective: Our purpose was to compare the intrinsic and extrinsic foot muscle size and strength in gymnasts (who predominantly train barefoot) and cheerleaders (who predominantly train shod). Another purpose was to measure time to stability for both groups shod and unshod. Design: Observational study. Setting: Human Performance Laboratory. Participants: 16 collegiate gymnasts (height = 159.3 ± 4.9cm, weight = 56.7 ± 4.3kg) and 16 collegiate cheerleaders (height = 161.9 ± 5.4cm, weight = 58.7 ± 7.1kg) volunteered for this study. Main Outcome Measure(s): The muscle size of 6 intrinsic and extrinsic muscles of the foot were measured using ultrasound, toe flexor strength, as assessed using a custom-made dynamometer, and time to stability following a drop landing, as assessed using ground reaction force data collected with force plates. Results: There were no significant group differences in great toe flexor strength (p = 0.274), lateral toe flexor strength (p = 0.824), or any of the time to stability conditions (p = 0.086 – 0.90). Only one muscle, fibularis longus, was significantly bigger in gymnasts than cheerleaders (p = 0.017) Conclusions: Our findings suggest that the barefoot training of gymnasts may not have as large of an impact on the foot musculature and strength as running barefoot or in minimalist shoes has on these factors.

The LeanScreenTM app uses photographs and touchscreen technology of an iPad or iPhone to estimate body composition using the Department of Defense (DoD) prediction equations that use cirumference measurements of the neck, abdomen, waist, and hips. The purpose of this study was to determine the validity and reliability of the LeanScreenTM app in 148 weight-stable adults (82 men, 66 women) who were normal weight, overweight, or obese as defined by body mass index. The percent body fat (%BF) of each subject was estimated during one visit using dual-energy x-ray absorptiometery (DXA) as the criterion measure, and three field methods: the LeanScreenTM app, manually measured circumferences, and an OMRON bioelectical impedance (BIA) device. The %BF of each subject was determined once using DXA. Each of two administrators assessed the %BF of each subject twice using the LeanScreenTM app, manually measured circumferences, and the OMRON BIA device. When using the LeanScreenTM app, administrators assessed body composition using photographs they had taken and the photographs taken by the other administrator. Validity was established by comparing estimates of %BF from the LeanScreenTM app, manually measured circumferences, and the OMRON BIA device to %BF values obtained from DXA. Inter- and intrarater reliability was determined using mutliple measurements taken by each of two administrators. The three field methods were compared to DXA using mixed model ANOVA and Bland-Altman analyses. Analysis of the data revealed that the LeanScreenTM app, manually measured circumferences, and the OMRON BIA device significantly underestimated (p < 0.05) the %BF determined by DXA by an average of -3.26 ± 3.57 %BF, -4.82 ± 3.45 %BF, and -8.45 ± 3.48 %BF, respectively. Limits of agreement (LOA) for the LeanScreenTM app (6.99 %BF), manually measured circumferences (6.76 %BF), and the OMRON BIA device (6.82 %BF) were large. Slopes of the line-of-best-fit through the data in the Bland-Altman plots indicate that bias of %BF estimates using the LeanScreenTM app (slope = 0.06; p = 0.008) and the OMRON BIA device (slope = 0.15; p < 0.0001) increased as %BF increased. For each method of assessment, minimal variance could be attributed to different administrators peforming the assessment and each administrator performing multiple assessments. All inter- and intrarater reliability coefficients of the LeanScreenTM app, manually measured circumferences, and OMRON BIA estimates of %BF exceeded 0.99. The results of this study indicate that all three field methods of body composition assessments were highly reliable, however, these field measures are not recommended for use in the assessments of %BF due to a significant bias and large limits of agreements.

Antagonism of the activin receptor signaling pathway represents a promising potential therapy for the muscular dystrophies and other muscle wasting disorders (i.e., cachexia or sarcopenia). Previous research has shown that antagonism of activin signaling promotes muscle growth, attenuates muscle wasting, and restores function in both wild type and diseased animals. Our laboratory has recently developed a novel small molecule (SGI-1252) that inhibits activin downstream (i.e., Smad2/3 phosphorylation) signaling. Purpose: In this study we determined how eight weeks of orally administered SGI-1252 affected TGF-ß signaling, whole body mass, individual limb muscle mass, and muscle fiber cross sectional area (CSA). Methods: Wild-type (WT) mice were treated with SGI-1252 or a vehicle control (VC) via oral gavage (400 mg/kg 3 times per week) for 8 weeks. Body mass was measured twice per week during the 8-week treatment period. At the end of the treatment period, gastrocnemius and tibialis anterior (TA) muscles were excised, weighed, and prepared for histological and biochemical analyses. Results: Following 8 weeks of treatment, there was no difference in weight gain between SGI-1252 (24.8 ± 1.8g) and VC treated mice (23.2 ± 1.5g) (p = 0.06). Gastrocnemius whole muscle mass was significantly greater in the SGI-1252 treated group relative to the VC treated mice (139.6 ± 12.8 mg vs 128.8 ± 14.9 mg) (p = 0.04), although when normalized with body mass there was no difference in gastrocnemius mass. For the TA muscle, there were no significant differences in whole muscle mass between SGI-1252 and VC groups, yet TA muscles in the SGI-1252 treated group had a reduced muscle fiber CSA compared to controls (621 ± 44 µm2 vs 749 ± 36 µm2) (p = 0.0005). There was a statistical trend of decreasing Smad2 phosphorylation in the SGI-1252 treated TA muscles (mean SGI-1252 = 0.668 vs VC = 0.848) (p = 0.06), and no significant differences in Smad2 phosphorylation in the gastrocnemius. Conclusions: Contrary to our hypothesis, 8 weeks of orally administered SGI-1252 was not effective in promoting increases in whole body mass, limb whole muscle mass, or myofiber cross sectional area. This may be due to the inability of SGI-1252, at the administered dose, to effectively decrease signaling downstream of the activin receptor. Clearly, studies using a wider range of doses and delivery methods will be needed to ascertain the efficacy of SGI-1252 as a potential therapeutic.

Purpose: To explore the difference between continuous and pulsed photobiomodulation (PBMT) versus a placebo treatment when using a red-blue light combination over multiple treatment sessions to decrease the symptoms of muscle damage in the quadriceps muscle after a bout of muscle damaging exercise. Methods: Thirty-six healthy, nonactive male and female participants were randomly assigned to one of three groups: continuous PBMT, pulsed PBMT, and placebo treatment. Participants were assessed for muscle damage with knee extension maximal isometric and isokinetic contractions, as well as Visual Analog Scale (VAS) and Lower Extremity Functional Scale (LEFS) scores. Blood creatine kinase (CK) was also analyzed. Participants were given treatment immediately prior to undergoing a bout of damaging eccentric exercise. Participants were treated with PBMT for the next 4 consecutive days for a total of 5 treatments. Results: The continuous treatment group lost significantly less isokinetic average peak torque than the placebo treatment when averaged across all time points postexercise. However, for isometric testing, the continuous group had more reduction in force compared to the placebo group. Between the treatment groups, the continuous treatment group had significantly more muscle soreness measured by the VAS and had significantly less function in daily tasks reported on the LEFS patient-oriented outcome scale. There was no significant difference in level of creatine kinase between the treatment groups. Conclusion: Pulsed photobiomodulation treatments had no significant effect when compared to the placebo group. Continuous photobiomodulation helped to reduce isokinetic force loss, yet exacerbated all other muscle damage markers following exercise relative to the placebo condition.

Context: Knee injury is a common problem for runners. Knee pain is a common symptom in knee injury and is associated with alterations in knee and hip muscle activation and hip joint angles. Relieving pain through intervention may help to restore neuromuscular function. Objective: To examine the effects of ice and transcutaneous electrical nerve stimulation (TENS) combination treatment on perceived knee pain, hip frontal plane angle, and muscle activation during running in individuals with experimental knee pain (EKP). Design: Crossover. Setting: Laboratory. Subjects: 19 participants (11 males and 8 females, 23.2 ± 1.9 y, 176 ± 11.6 cm, 71.5 ± 16.9 kg; right leg dominant). Interventions: Hypertonic saline was infused into the infrapatellar fat pad for 74 minutes (total 11.1 mL). Subjects underwent 2 treatment conditions (sham; ice/TENS combination). Measurements were recorded during running at 4 time points (preinfusion, postinfusion, posttreatment, and postinterval). Main Outcome Measures: Perceived knee pain on a 100-mm visual analog scale (VAS), knee and hip muscle peak electromyography (EMG) amplitude, and hip adduction angles. Results: Hypertonic saline infusion increased perceived anterior knee pain in all participants. The average of peak perceived knee pain was 28 mm on a 100-mm VAS in EKP application. While the increased perceived knee pain level stayed consistent across time in the sham session, ice/TENS combination treatment significantly reduced perceived knee pain by 35% at 6 minutes after the treatment start (p = 0.049), and the reduced knee pain lasted for 22 minutes (p > 0.05). Peak EMG amplitude of the gluteus medius was decreased by 13.5% and 14.3% (p = 0.023; p = 0.013) during running after EKP in sham and treatment sessions, respectively. However, the peak EMG amplitude was not restored to pain-free level during running after the treatment (p = 0.026). No other muscles changed their peak EMG amplitude due to EKP or treatment. Hip adduction angles during running were also not altered by EKP or treatment (p > 0.3) in both sham and treatment sessions. Conclusions: EKP increased perceived knee pain and decreased peak muscle activation of the gluteus medius during running. Ice/TENS combination treatment reduced perceived knee pain quickly, but did not restore neuromechanics during running.

The purpose of this dissertation was to examine the existence of force production and strength symmetry while concentrating on its role with performance. Specifically, in this dissertation I sought to determine if differences in symmetry exist between male and female athletes as well as between athletes of different strength levels. Various symmetry assessments were used and the amount of carryover between tests was also evaluated. Furthermore, the relationship between asymmetry magnitude and various aspects of jump performance was also assessed. The results showed that female athletes were more asymmetrical than their male counterparts for most assessments. Interestingly, weaker athletes regardless of gender were more asymmetrical than stronger athletes for all assessments. Symmetry characteristics appeared to carryover between all tests and conditions with the exception of the bilateral strength assessment. When separated by strength level, good carryover of explosive strength symmetry characteristics was noted. A trend of negative relationships was noted between jump performance and kinetic asymmetry, measured during jumps and weight distribution. Isometric mid-thigh pull force production asymmetry did not relate to jump performance as it had previously. Kinetic asymmetry was shown to influence the direction of center of mass displacement (COMd). Specifically, asymmetrical rate of force development showed the most ability to differentiate between values of COMd in the mediolateral direction. The finding that female athletes are more likely to produce force asymmetrically may indicate that they are more susceptible to the performance detriments that accompany force production asymmetry. This may also indicate that female athletes are more susceptible to injury if force asymmetry is an injury predictor. However, differences in asymmetry magnitude between the sexes may be due to differences in strength level between the sexes in the current study, as weaker athletes were shown to be more asymmetrical than their stronger counterparts. Thus, it may be inadequate strength level that is a risk factor to performance detriments and possible injury. It also appears that force production asymmetry can both alter and hinder optimal jump performance. In order to optimize performance and possibly reduce injury risk, it is recommended that weaker athletes focus on bilateral strengthening exercises.

The purpose of this dissertation was to describe the basic characteristics of performing resisted sprint training using a push sled for the enhancement of sport performance. Specifically, this dissertation served to: 1.) quantify the frictional forces involved between a push sled and an AstroTurf® surface at 6 loads, 2.) derive an estimation of mechanical work performed during sled push training, 3.) outline the velocity characteristics of 3 sled pushing loads scaled to the athletes body mass for comparison against their sprinting ability and 4.) determine the interrelations of fitness characteristics to the ability to sprint under heavy resistance. The following are major findings of this dissertation. 1.) Coefficients of static friction (0.53 – 0.37) and dynamic friction (0.35 – 0.28) were calculated at multiple loads for the AstroTurf® surface. 2.) A direct near perfect relationship exists between total system load of the sled and the forces required to initiate and maintain movement of the sled. Although a direct measurement of force would be more precise and account for changes in velocity, the total system load may be a more practical alternative for daily use. 3.) Statistically significant changes in velocity characteristics were observed within each sled pushing load as well as when comparing each load to sprinting. Decrements in peak velocity ranged from about 40%-51% when comparing resisted to unresisted sprinting. Load increments of 25% body mass were heavy enough to cause statistically significant differences in velocity characteristics. 4.) Statistically significant correlations were observed in anthropometry, sprinting ability, jumping ability, and strength to sled pushing. The results indicate that larger athletes, who can not only produce greater force but produce those forces rapidly, in addition to excelling at jumping and sprinting compared to their peers demonstrate the ability to move faster against heavy loads and slow down less from unresisted conditions. The strongest athletes demonstrated statistically nonsignificant differences in peak velocity drop off when compared to their weaker counterparts; however, small to moderate effect sizes (d = 0.27 – 1.02) were observed indicating a practical difference between strength levels in peak velocity and peak velocity drop off.

The purpose of this dissertation was to evaluate the effects of changing body position on the execution of the isometric mid-thigh pull (IMTP). Furthermore, while there is evidence to suggest that there is an effect of familiarization on performance of maximal strength tests, there has been no known research evaluating the effect of learning on the IMTP. The effect of familiarization was assessed by evaluating changes in variables obtained from the IMTP. Subjects did not statistically improve over the five IMTP testing sessions, regardless of the body position used, or if subjects had previous experience with weightlifting derivatives. This may indicate that little familiarization is needed for subjects to perform the IMTP before acute increases due to learning stabilize. When body positions were compared, there were differences in force production whether subjects had or did not have experience with weightlifting movements. The magnitude of difference between body position was affected by weightlifting movement experience; lifters with >6 months experience with weightlifting had larger differences in force production between position. Average muscle activation for a variety of muscles, evaluated with surface EMG, appeared to differ between body positions, although these positions are idiosyncratic to experience level. In particular, lumbar erector spinae activation was higher in the bent position for both groups, which may have implications for low back injury risk.In entirety, it appears that if maximizing force production is the goal, the upright positon is optimal. Furthermore, the differing body positions have meaningfully different effects on how 3 much individual muscles are activated between positions. Lastly, substantial familiarization does not appear to be necessary before subjects perform the IMTP.

The purpose of this dissertation was to determine if a there was a dose-response relationship across an NCAA Division I men’s soccer season. Specifically, this dissertation serves to: 1.) assess the validity of duration measurements that have previously been used to calculate session RPE during competitive matches, 2.) determine the degree and magnitude of change in intermittent endurance performance across a season and to observe how change in endurance relates with training load, 3.) determine the degree and magnitude of change in strength and explosiveness across a season, and to see how these strength changes relate to training load. 1.) Minutes played were found to be the most accurate duration for calculating session RPE during men’s NCAA Division I soccer matches. 2.) Endurance performance, measured using the Yo-Yo IR1, increased by an average of 14 percent from pre to post season. Furthermore, a large, negative relationship was observed between training load and change endurance performance. These relationships suggest that excessive accumulation of training load can impair endurance performance. The congested NCAA DI match schedule may make it difficult to prevent excessive training loads. 3.) When players were grouped by amount of college soccer experience (upper and underclassmen), upperclassmen jumped significantly higher than underclassmen during the preseason. Moreover, the upperclassmen maintained or increased jump height from pre to post season, while underclassmen experienced a general decrease in jump height from pre to post season. Moderate relationships indicate a positive relationship between training load from resistance training and changes in strength. Likewise, these same relationships strengthened in the players who received more playing time during matches. Taken together, the high numbers of moderate relationships indicate a high level of individual variability. Dose-response relationships with strength variables were not sufficiently established. The overall findings of this dissertation provide evidence that subjectively and objectively monitoring training load and soccer-related performance variables can assist coaches in making decisions that will promote the welfare of their team.

Functional magnetic resonance imaging (fMRI) can be used to track neural activation in the brain during functional activities. The purpose of this study was to investigate brain neural responses to blood flow restricted (BFR) versus control handgrip exercise. Using a randomized crossover design, 25 subjects (12 males, 13 females) completed handgrip exercises during two conditions: BFR vs. control. To familiarize participants with the exercise conditions, one week prior to MRI scanning participants completed each exercise condition once on separate days, with 72 hours between days. The following week fMRI scans were performed at the same time of day, separated by 72 hours. The exercise protocol consisted of five 30-second sets of squeezing a nonmetallic handgrip exerciser (a reported 13.6 kg resistance), doing as many repetitions as possible, with 20-second rest intervals between sets. We saw a significant main effect of exercise condition (BFR versus control) between premotor dorsal (PMd)(F = 5.71, p = 0.022), premotor ventral (PMv)(F = 8.21, p = 0.007), and right ventral striatum (VS_R)(F = 7.36, p = 0.01). When considering anatomical regions of interest, we did not find significant differences between exercise conditions in bilateral S1 (p > 0.82), primary motor cortex (M1)(p > 0.33), supplementary motor area (SMA)(p > 0.66), cerebellum (CB)(p > 0.70), insular cortex (INS)(p > 0.45), anterior cingulate cortex (ACC)(p > 0.24), or thalamus (TH)(p > 0.66). Bilateral ACC (ACC_B), right middle frontal gyrus (MFG_R), and the right primary sensory cortex (S1_R) showed significant linear trends (p = 0.001) over the five exercise sets. Finally, the S1_R, left primary sensory cortex (S1_L), and the right anterior cingulate cortex (ACC_R) showed a main effect of set (p < 0.02). These data demonstrate that acute training with BFR during handgrip exercise results in different neural activation patterns in select areas of the brain, compared to a control. These results show that while completing less work with BFR exercise, subjects can achieve a similar amount of brain neural activation as with a higher-volume exercise. Brain neural activation is important to overall patient health and these findings may be important for prescribing training with BFR in clinical and applied research settings.