Abstract available in the 10th Annual Coaches and Sport Science College .

There has been much debate on the benefits of a forefoot versus rearfoot strike pattern in distance running in terms of performance and injury prevalence. Shock attenuation occurs more prominently in soft tissues at impact in forefoot runners compared to the passive skeletal loading in rearfoot runners. Recent studies indicate that a forefoot strike pattern may not be maintainable over long distance efforts. Therefore, this study tested the hypothesis that habitual forefoot runners could not maintain their strike pattern throughout a prolonged, intensive run. Fourteen forefoot runners ran to voluntary exhaustion on an instrumented force treadmill (average run duration: 15.4±2.2 minutes). Kinematic and kinetic data were sampled each minute at 200Hz and 1000Hz, respectively. Ankle plantar-flexor torque was measured during pre- and post-run isometric contractions, during which electromyographic activity was measured in the soleus, lateral, and medial gastrocnemius. Loading rate (49.95±14.83 to 57.40±22.53 BW*s-1, p=0.0311) and impact peak (1.35±0.43 to 1.50±0.51, p=0.0207) increased significantly throughout the run. Both peak knee flexion (-33.93±3.67º to -36.21±3.48º, p=<0.0000) and sagittal ankle angle at touchdown (-11.83±5.33º to -9.33±6.29º, p =0.0202) increased significantly. Ankle torque decreased significantly from pre- to post-run (120.57±33.57 to 110.76±32.91 Nm, p = 0.0154). This was accompanied by a decrease in medial and lateral gastrocnemius integrated electromyographic activity (iEMG) (p=0.0387 and 0.0186, respectively). The results indicated that there were significant changes in landing mechanics in the habitual forefoot runners with increased levels of exertion, as they shifted towards strike patterns more similar to rearfoot runners throughout the run. These changes are in line with metabolic findings of other studies. There is increased eccentric loading of the ankle plantar-flexor muscles at touchdown in forefoot runners that may contribute to a decreased torque output by the end of the run. The decline in iEMG may indicate altered central drive of the system and a decline in the impact attenuation ability of the triceps surae, leading to the changes exhibited up the kinematic chain. These findings suggest that while forefoot strike patterns are good for speed, the onset of fatigue may affect the ability to maintain this pattern during a prolonged, intensive effort.

Runners adopt altered gait patterns as they fatigue which may increase energy expenditure and susceptibility to certain overuse injuries. Previous investigations have described changes in muscle performance and kinematic gait variables resulting from running fatigue. The purpose of this investigation was to characterize changes in joint moment patterns that develop as runners fatigue in order to better understand the kinetic bases for kinematic fatigue effects. It was hypothesized that when fatigued, runners would demonstrate increases in stance time, peak stance phase knee flexion angle, peak knee extension moment, peak swing phase hip flexion moment, and hip extension and plantarflexion angular impulse generated during stance. Eight recreational rearfoot-striking runners (height = 170.0 ± 9.8 cm; mass = 69.6 ± 15.1 kg) ran on a force-instrumented treadmill at a velocity 5% slower than that of lactate threshold until volitional exhaustion. Force and motion data were collected each minute and analyzed at six evenly-spaced time points over the run duration. Of the six hypotheses, only stance time changed significantly (p = 0.004), increasing in a linear manner over the course of the run (r2 = 0.946). Of the remaining hypotheses, peak knee flexion (r2 = 0.899) and hip extension angular impulse (r2 = 0.608) followed increasing trends over the course of the run. Individual participants often demonstrated joint moment trends consistent with fatigue effects reported in the literature, despite inconclusive group results. High variability in individual responses underscores the complexity of gait adaptations used by distance runners as they fatigue.

INTRODUCTION: Sensory systems within the head provide us with rich perceptual information and may require complex control of the head during locomotion when changing direction. Head position in space is maintained by head on trunk motion as well as lower extremity kinematic modifications, such as increased knee flexion and increased stance time in order to facilitate shock attenuation and reduce vertical CoM displacement. It has been established that the body organizes its degrees of freedom of the trunk, pelvis and lower extremities differently during anticipated and unanticipated sidestepping, which raises the question of how these modifications affect head control during change of direction tasks. METHODS: Fourteen collegiate soccer players performed 7 anticipated and 7 unanticipated sidestepping tasks. Kinematic data were recorded using an 11-camera motion capture system (Qualysis, Inc., Gothenburg, Sweden) sampling at 240 Hz. Head and trunk orientation was quantified at penultimate toe off. A modified vector coding analysis was used to quantify the coordination and coordination variability between the head and trunk during the anticipated and unanticipated side-stepping trials. Differences in head-trunk orientation and coordination pattern frequencies were assessed with a paired t-test with an . One-dimensional statistical parametric mapping (SPM1D) was used to compare coordination variability waveforms. RESULTS: The head (p < 0.01, ES = 0.82) and trunk (p < 0.05, ES = 0.59) were significantly more oriented toward the new travel direction during anticipated compared to unanticipated sidestepping. No significant differences in transverse or sagittal plane coordination were observed throughout the change of direction stride. However, during unanticipated sidestepping we observed significantly reduced in-phase head-trunk coordination during the preparatory phase in the sagittal (p = 0.04, ES = 0.63) and transverse (p = 0.02, ES = 0.73) planes but did not find differences in the stance or post-transition phases. Coordination variability did not differ between anticipated and unanticipated conditions. Irrespective of planning time, greater transverse plane coordination variability was observed during the flight phases compared to the stance phase (p < 0.01) of the change of direction stride. Sagittal plane coordination variability was significantly greater during the preparatory phase than the stance phase (p < 0.01), and stance phase coordination variability was significantly greater than post-transition phase variability (p < 0.01). SIGNIFICANCE: Our results suggest differences in coordination between the head and trunk between anticipated and unanticipated sidestepping emerge during the preparatory phase of the change of direction stride, from penultimate step toe off to transition step heel strike. Anticipated and unanticipated sidestepping are different tasks, but individuals are consistent in the way the head-trunk coupling is controlled. Relating variability to task goals may allow for a better understanding of the beneficial aspects of variability observed at the head.

Biomechanical and physiological parameters related to running performance are usually studied separately. However, evaluating both aspects together could be beneficial in improving athletic performance. The purpose of this study was to observe the change in peak vGRF and asymmetry as speed increases, while observing physiological responses during a O2maxtest. Data from athlete monitoring of 12 cross-country and triathlon athletes were analyzed. The athlete monitoring protocol included three unweighted countermovement jumps and a O2maxtest performed by the athletes. The athletes had an average O2maxof 53.4 ± 7.7 mL/kg/min, while their average vGRF asymmetry throughout the O2maxtestwas 1.38 ± 0.68%. A strong, positive correlation was found between average vGRF and average blood lactate (r=0.93), indicating that as vGRF increased so did blood lactate. It was concluded that physiological and biomechanical parameters are related in athletic performance. Therefore, athlete monitoring should include analysis of both physiological and biomechanical parameters in order to form a more well-rounded analysis of athlete performance.

The purpose of this study was to examine the effects of vertically-oriented resistance training on golf driving performance. Ten Division-I collegiate golfers completed 2 resistance training sessions per week for 10 weeks during the fall tournament season. Pre- and posttraining assessments of strength-power and golf performance were compared. To assess strength-power, jump height, peak force, and peak power (PP) were measured from static and countermovement (CMJ) vertical jumps; peak force and rate of force development from 0-250 ms were measured from an isometric mid-thigh pull. Golf performance was assessed in terms of ball launch speed (BS), spin rate, carry yardage (CY), and total yardage (TY), averaged from 5 shots using a driver. Following training, all measures of strength-power improved, with CMJ PP improving significantly (p<0.00625). The golf performance assessment indicated significant increases (p<0.0125) in BS, CY, and TY. These results suggest that vertically-oriented resistance training can improve golf driving performance.

It is critical to maintain multiple fitness characteristics during the soccer season through the use of training, but also to ensure that the training loads do not hinder subsequent match performance. The purpose of this thesis is to investigate the impact of the training load on key physical performance variables in the subsequent match. Five Division I female soccer players were analyzed across six weeks of training and matches. Training loads in the forms of odometer, high intensity odometer, estimated odometer and sRPE were accumulated at time points from one to five days prior to a match. The accumulated training loads were then correlated with the same performance measures from match play. The greatest significant correlations were seen in sRPE training loads when compared to match odometer and estimated distance. There does not appear to be negative effect on match performance when looking at any of the accumulated training load values.

Physiological performance has been commonly scaled for body size using various methods to scale anthropometrics, but a paucity of data exists on scaling muscle size. The aim of this thesis was to elucidate the optimal method to scale height (HT), body mass (BM), lean body mass (LBM), and muscle cross-sectional area (CSA) when scaling weightlifting performance for body size. 26 weightlifters (13 male, 13 female) participated in this study. The measurements collected were the snatch (SN), clean and jerk (CJ), isometric peak force (IPF), and countermovement jump height (CMJH). HT, LBM, BM, and vastus lateralis CSA were scaled using the ratio standard and allometry. Competition performance scaled for allometrically scaled CSA possessed greater relationships to CMJH (r = 0.60 – 0.78) than the ratio standard (r = 0.56 – 0.58). These findings suggest that allometrically scaling CSA may be superior when scaling weightlifting performance for CSA.

The main problem of this study was to determine if a significant strength difference existed between the mirror muscles of six muscle groups in the dominant and nondominant legs of University of the Pacific male soccer players at differing contraction speeds as measured by the Cybex II Isokinetic Dynometer.

"Training is a process and there's a lot more to it than simply sets and reps." Respected strength coaches Mike Stone and Meg Stone discuss periodization and programming for strength power athletes at the 2012 NSCA Coaches Conference.