Mark Goss-Sampson

Effects of a Low Volume Injury Prevention Program on the Hamstring Torque Angle Relationship

The effects of a 4-week lower body injury prevention program on knee muscle torque–angle relationship were examined in soccer players. Twenty men were randomly allocated to either a control (n = 10) or training group (n = 10). The training group underwent three training sessions per week, comprising 3 sets of 8 repetitions of one open-chain exercise (Nordic curl) and two closed-chain exercises—forward lunges on a Bosu® balance trainer and eccentric single leg dead lifts. Maximal peak knee flexion torque was measured at 35°, 45°, 60°, 80°, 90°, and 100° pre- and post-intervention. Significant improvements were observed only at 80° (p = .001; d = .94) along with a nonsignificant trend at 35° (p = .081; d = .43). As these modifications might protect athletes against muscle and joint injuries, the use of both stable-open and unstable-closed kinetic chain exercises emphasizing eccentric hamstring and knee stabilization actions should be integrated into injury prevention programs in team sports athletes.

Retinal abnormalities in experimental vitamin E deficiency.

Physiological and biochemical studies have been carried out longitudinally over a period of 12 months in vitamin E deficient and control rats to gain an understanding of the mechanism whereby vitamin E conserves normal retinal function. Electroretinographic studies indicated that the primary effect of vitamin E deficiency was on the photoreceptors. Ultrastructural studies, however, did not show any morphological changes to the photoreceptors which could explain receptor dysfunction. A 30-40% loss of vitamin A (retinol) was found to be associated with vitamin E deficiency. This could be corrected by repletion with vitamin E, but there was no associated improvement in visual function. An irreversible loss of the long-chain polyunsaturated fatty acids from the retina, increased lipid peroxidation and alterations in membrane fluidity were also detected during vitamin E deficiency. We suggest that a deficiency of vitamin E leads to changes in the membrane microenvironment, which could affect photo transduction by either impairing the ability of rhodopsin to undergo conformational changes to the active form, or by disrupting the hyperpolarising and depolarising processes of the photoreceptors.

The Effectiveness of Injury Prevention Programs to Modify Risk Factors for Non-Contact Anterior Cruciate Ligament and Hamstring Injuries in Uninjured Team Sports Athletes: A Systematic Review

Background Hamstring strain and anterior cruciate ligament injuries are, respectively, the most prevalent and serious non-contact occurring injuries in team sports. Specific biomechanical and neuromuscular variables have been used to estimate the risk of incurring a non-contact injury in athletes. Objective The aim of this study was to systematically review the evidences for the effectiveness of injury prevention protocols to modify biomechanical and neuromuscular anterior cruciate and/or hamstring injuries associated risk factors in uninjured team sport athletes. Data Sources PubMed, Science Direct, Web of Science, Cochrane Libraries, U.S. National Institutes of Health clinicaltrials.gov, Sport Discuss and Google Scholar databases were searched for relevant journal articles published until March 2015. A manual review of relevant articles, authors, and journals, including bibliographies was performed from identified articles. Main Results Nineteen studies were included in this review. Four assessment categories: i) landing, ii) side cutting, iii) stop-jump, and iv) muscle strength outcomes, were used to analyze the effectiveness of the preventive protocols. Eight studies using multifaceted interventions supported by video and/or technical feedback showed improvement in landing and/or stop-jump biomechanics, while no effects were observed on side-cutting maneuver. Additionally, multifaceted programs including hamstring eccentric exercises increased hamstring strength, hamstring to quadriceps functional ratio and/or promoted a shift of optimal knee flexion peak torque toward a more open angle position. Conclusions Multifaceted programs, supported by proper video and/or technical feedback, including eccentric hamstring exercises would positively modify the biomechanical and or neuromuscular anterior cruciate and/or hamstring injury risk factors.

The effects of maximal and submaximal arm crank ergometry and cycle ergometry on postural sway

Abstract This study aimed to determine whether arm crank ergometry (ACE) disturbed postural sway to the same extent as cycle ergometry (CE). Nine healthy, none specifically trained adults undertook posturographic tests before and after five separate exercise trials consisting of: two incremental exercise tests to exhaustion for ACE and CE to examine postural sway responses to maximal exercise and to determine peak power output (Wmax); two subsequent tests of 30 min duration for ACE and CE at a relative workload corresponding to 50% of the ergometer-specific Wmax (ACErel; 53 ± 8 W and CErel; 109 ± 16 W). A final CE trial was performed at the same absolute power output (CEabs) as the submaximal ACE trial to match absolute exercise intensity (i.e., 53 ± 8 W). The centre of pressure (COP) displacement was recorded using a force platform before, immediately after exercise and during a 30-min recovery period. ACE had no effects on postural sway (P > 0.05). An increase in mediolateral COP displacement was observed following maximal CE only (P = 0.001), while anteroposterior COP displacement and COP path length increased following maximal and submaximal CE (P < 0.05). These differences in postural sway according to exercise mode likely stem from the activity of postural muscles when considering that CE recruits lower limb muscles involved in balance. This study provides evidence of an exercise mode which does not elicit post-exercise balance impairments, therefore possesses applications to those at an increased risk of falling.

Kinematic analysis of netball goal shooting: A comparison of junior and senior players

Abstract The aim of this study was to investigate the effect of playing experience on the kinematic characteristics of the goal shooting action in netball players. Six county-level junior and six senior goal shooters took part in the study. They were asked to perform eight shots at goal and were equipped with 33 retro-reflective markers fixed to anatomical landmarks for three-dimensional motion tracking. The shot was divided into three periods: start of throw, shooting action, and release. The following variables were determined for each period: position of the ball, joint angles, timings between actions, joint angular velocities, and ranges of motion. The main results showed a significant effect of playing experience, with senior shooters showing a shorter delay between the movements involved in the shooting action, a significant difference between the right and left elbow angles at the start of forearm extension, and greater extension of the left shoulder and greater flexion of the left elbow at release compared with junior shooters. These results might help justify some of the empirical observations made by coaches and direct them in their advice to players. In particular, recommendations to junior players should focus on the simultaneity of leg and arm actions and dissociation between the right and left arms during the shooting action.

Effect of a carbohydrate-protein multi-ingredient supplement on intermittent sprint performance and muscle damage in recreational athletes

Carbohydrate-protein-based multi-ingredient supplements have been proposed as an effective strategy for limiting the deleterious effects of exercise-induced muscle damage. This study compares the effects of a commercially available carbohydrate-protein supplement enriched with l-glutamine and l-carnitine-l-tartrate to carbohydrate alone or placebo on sprint performance, muscle damage markers, and recovery from intermittent exercise. On 3 occasions, 10 recreationally trained males ingested a multi-ingredient, a carbohydrate supplement, or a placebo before, during, and immediately after a 90-min intermittent repeated sprint test. Fifteen-metre sprint times, creatine kinase, myoglobin, and interleukin-6 were assessed before (pre), immediately after (post), 1 h after (1h), and 24 h after (24h) exercise. Total sprint time measured during the intermittent protocol was not different between conditions. Fifteen-metre sprint time was slower (p < 0.05) at post, 1h and 24h compared with pre without differences between conditions (p > 0.05). Creatine kinase at 24h was lower (p < 0.05) in the multi-ingredient (461.8 ± 271.8 U·L) compared with both carbohydrate and placebo (606 ± 314.5 U·L and 636 ± 344.6 U·L, respectively). Myoglobin increased (p < 0.05) in all 3 conditions at post and 1h compared with pre, showing lower values at 1h (p < 0.05) for the carbohydrate and a trend (p = 0.060) for multi-ingredient compared with the placebo condition (211.4 ± 127.2 ng·mL(-1) and 239.4 ± 103.8 ng·mL(-1) vs. 484.6 ± 200.0 ng·mL(-1), respectively). Interleukin-6 increased at both post and 1h compared with pre (p < 0.05) with no differences between conditions. In conclusion, ingesting a multi-ingredient supplement before, during, and immediately after a 90-min intermittent sprint test resulted in no effects on performance and fatigue while the accumulation of some biomarkers of muscle damage could be attenuated.

The influence of whole body vibration on the central and peripheral cardiovascular system

The purpose of this study was to investigate the physiological changes of the cardiovascular system in response to whole body vibration during quiet standing and identify whether there is a greater influence on the central or peripheral cardiovascular system. Twenty healthy participants (12 male and 8 female) were assessed over two separate testing sessions for changes in peripheral skin temperature, peripheral venous function, blood flow velocity in the dorsalis pedis artery, blood pressure and heart rate during quiet standing with 40 Hz 1·9 mm synchronous vibration. Vibration exposure totalled 5 min in 1 min increments with 5 min recovery during each testing session. There were no significant changes in heart rate, blood pressure or peripheral skin temperature. Significant results were obtained for blood flow velocity with increases from 0·5 + 0·2 cm·s−1 at baseline to 1 + 0·2 cm·s−1 during vibration, returning to baseline levels during the recovery period. Due to the absence of changes in heart rate, blood pressure or lower leg and foot temperature, the change in blood flow velocity can be attributed to changes in peripheral vascular function. The results suggest a high level of sensitivity of the peripheral vascular system to vibration exposure; therefore, further studies should be completed to ascertain the physiological mechanisms underlying the effects of vibration on the peripheral vascular system.

Temporal and kinematic analysis of the rotational shot put technique

Kinematic data provide the biomechanist with valuable information to analyse athletic performance. The reduction and analysis involved in generating the data is often provided by commercially available hardware and software. To have confidence in any analysis, the system should first be validated. Several of these software systems have been evaluated previously for accuracy; however, no evaluation has been made of the SIMI Motion system (SIMI Reality Motion Systems, Unterschleissheim, Germany). The aim of this study was to determine the accuracy of the data derived using SIMI Motion. A calibration rig was constructed of four markers. Three markers were located in the horizontal plane, with one fixed at the origin and the other two located 400 mm from the origin at 908 to each other and free to rotate at 60 rev×min. The fourth marker was fixed at 300 mm in the horizontal and –18 mm in the vertical from the origin. A calibration frame (2.2, 1.9 and 1.6 m; Peak Performance Technologies Inc., Englewood, CO) was filmed in three dimensions at 50 Hz using two Sony DCR-TRV900E digital cameras. Within the calibration volume, the rig was filmed at two extreme positions and at two heights (ground level and elevated by 870 mm) for 6 s in a dynamic mode (i.e. the two markers rotating at 60 rev×min). In addition, the rig was filmed once at position A, located at ground level furthest away from the camera, while static. The four markers were manually digitized and analysed using SIMI Motion version 6.0. The data were smoothed using a second-order low-pass filter with a cut-off frequency of 3.475 Hz, determined using the equation recommended by Yu et al. (1999: Journal of Applied Biomechanics, 15, 318–329). Distances, angles and angular velocities were obtained for several fixed and variable measurements and the mean absolute errors were calculated. The results for the final 3 s of the dynamic mode data capture at position A were (criterion+mean absolute error): fixed distance, 400+7 mm; fixed angle, 90+28; angular velocity of the fixed angle, 0+0.33 rad×s; angular velocity of the rotating arm, 6.28+0.85 rad×s. The mean absolute error of 7 mm for the fixed distance compares favourably with the 12 mm reported by Ehara et al. (1997: Gait and Posture, 5, 251–255) for the APAS system (Ariel Dynamics Inc., Trabuco Canyon, CA) and the 18 mm for the Dynas 3D/h system (Shin Oosaka Shoukai, Osaka, Japan). However, this error is greater than the 4 mm reported for the Peak 5 system (Peak Performance Technologies Inc.). The mean absolute error of 28 compares favourably with the root mean square error of 2.18 reported by Richards (1999: Human Movement Science, 18, 589–602) for the APAS system. The mean absolute error is, however, not directly comparable, as it provides a predictably larger value than the root mean square error, depending on the number of samples used in the calculation of the latter. The data were less variable for the angular velocity of the fixed angle than for the angular velocity of the rotating arm. However, the angle definition used to calculate the angular velocity of the rotating arm produced maximum and minimum angles that subsequently resulted in changes in direction of the angular velocity. On removing four samples at the change of direction of the angular velocity, the mean absolute error of the angular velocity of the rotating arm was reduced to the same error as for the angular velocity of the fixed angle (that is, +0.85 to +0.33 rad×s). In summary, the accuracy of the linear and angular position data of the SIMI Motion system compares favourably with that of other similar manual digitizing systems. However, the results of the first derivative may magnify any errors and care should be taken when interpreting such values. In producing any derivative data, the analysis also emphasizes the importance of Journal of Sports Sciences, 2003, 21, 235–365Proprioceptive neuromuscular facilitation (PNF) stretching techniques are becoming more popular among athletes, since they provide (possibly only temporary) increases in joint range of movement compared with other methods. However, other effects – in particular the effects upon the proprioceptive system and its subsequent role in motor control – have not been recorded. The aim of this study was to establish if there are any significant changes in postural sway after the application of a lower limb PNF stretching session.The Raman spectra of the ammonia-borane complex, NH3BH3, have been investigated as a function of pressure up to 40 kbar. Vibrational modes involving the NH3 group show negative pressure dependences, supporting the existence of the dihydrogen bond, but the vibrations of the BH3 group have a positive dependence. Two transitions were observed in the solid phase under pressure, in contrast to the temperature behavior, where a single transition occurs. Factor group splitting occurs for the degenerate vibrations, and this allows the correct assignment of the observed vibrations.Optimal release variables (angle, velocity and height) in the shot put have been studied extensively. The importance of selected temporal, kinetic and kinematic variables in the glide technique have been reviewed comprehensively (Zatsiorsky, 1990: In Techniques in Athletics, edited G.P. Bruggeman and J.K. Ruhl. Koln: Deutsche Sporthochschule); however, there is very little data on the rotational shot put technique. The aim of this study was to establish whether there are any significant relationships between distance thrown and selected temporal and kinematic components of the rotational shot put technique.

Effects of two different injury prevention resistance exercise protocols on the hamstring torque-angle relationship: a randomized controlled trial

The effects of two different 6-week lower body injury prevention programmes on knee muscle torque–angle relationship were examined in soccer players. Thirty-two men were randomly assigned to three groups: hamstring-eccentric (ECC) (n = 11), unstable-squatting (UNS) (n = 11), and control (n = 10). Intervention groups performed three training sessions per week using only three ECC or UNS exercises, respectively. Maximal peak knee flexion torque was measured at 35°, 45°, 60°, 80°, 90°, and 100°, pre- and post-intervention. Peak torque increased at 35° (P = 0.034, Cohen’s d = 0.67) and 45° (P = 0.004, Cohen’s d = 0.96) in the ECC group, and at 60° (P = 0.024, Cohen’s d = 1.16), 80° (P = 0.018, Cohen’s d = 1.21), and 90° (P = 0.001, Cohen’s d = 1.38) in the UNS group. As these specific modifications might respectively and differentially protect athletes against hamstring and knee-joint injuries, the integration of both types of exercises should be considered when designing injury prevention programmes for soccer players.

The effectiveness of different exercises protocols to prevent the incidence of hamstring injury in athletes

Hamstring strains are the most prevalent non-contact injury associated with participation in sports. In addition to the anatomical and functional characteristics of the hamstrings, such as the biarticular organisation or the dual innervations of biceps femoris, a number of alterable and non-alterable factors have been associated with the risk of hamstring injuries in athletes. Each of these variables would impact upon hamstring injury risk within an integrated approach, by which the possibility of sustaining an injury can vary depending on the particular circumstances of each athlete. The aim of this critical review is to examine the effects of current preventative exercise protocols and to provide basic guidelines for hamstring injury prevention in athletes.