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DO ELITE RUGBY PLAYERS WITH REPEATEDLY INJURED HAMSTRINGS DEMONSTRATE ALTERED GLUTEAL-HAMSTRING
RECRUITMENT PATTERNS WHEN SPRINTING?Brett, A.N., McGuigan, M.P.
University of Bath Introduction Acute hamstring injuries are the most prevalent muscle injuries in sport, and recurrence figures remain high. GlutealHamstring recruitment has been proposed as a potential risk factor for hamstring injury susceptibility (Jonkers et al., 2003), and delayed activation of gluteus maximus was demonstrated in hamstring injured vs non injured legs during a single-leg stance (Sole et al., 2011). No recent research has addressed activation and recruitment patterns during sprinting, the main provocative event in many hamstring injuries. The aim of this study was therefore to investigate the timing and magnitude of activation of gluteal and hamstring muscle groups during sprinting in elite rugby players, with and without a history of hamstring injury. Methods A two-way repeated measures design assessed the effect of injury on gluteal activation delay and the magnitude of activation, at different phases of the sprint. Two groups of elite rugby players were used: a control group with no previous history of hamstring injury (n=9); and a hamstring-injured group who had a history of more than one hamstring strain but were currently fit for selection (n=6). EMG signals from gluteal and hamstring muscles were recorded at 1000Hz using Myontec Pro EMG shorts (Myontec, Finland), during three maximal 50m sprints on an outdoor artificial grass surface. EMG data were analysed for the relative timing of the onset of the gluteal muscles compared to the hamstring muscles and the average rectified EMG (AREMG) over a stride for both muscle groups during the acceleration, maximal velocity and deceleration phases of the sprints. Results When considering all phases of the sprint together there were no significant differences in outcome measures between the hamstring injury and control groups. However, there were large effect sizes for a greater delay in gluteal activation onset (d = 0.88) and greater gluteal AREMG (d = 0.93) in the hamstring injury group compared to the control. Discussion Although there were no significant differences between the two groups, the large effect size for a delay in gluteal activation in the hamstring injury group provides some support to the hypothesis, and suggests that the question warrants further investigation with a larger sample size.
The large effect size for a greater mean gluteal AREMG in the hamstring injured group compared to the control group suggest that professional rehabilitation and return to play programmes, with a strong gluteal re-education emphasis may have been effective in increasing gluteal activation, but not in initiating this prior to the hamstrings. References Jonkers, I., Stewart, C., Spaepen, A. (2003) Gait and Posture 17, 264-272 Sole, G., Milosavljevic, S., Nicholson, H., Sullivan, S.J. (2012) BJSM 46, 118-123
PROPENSITY OF CONTACT EVENTS TO CAUSE INJURY IN RUGBY UNIONStokes, K.A., Roberts, S.P., England, M., Trewartha, G.
University of Bath Introduction Approximately 80% of all injuries sustained during rugby union matches are associated with contact events. Typically, injury incidence rate is reported per unit of time (e.g., per 1000 player hours), but expressing incidence rate per contact event gives an indication of the relative risk of each type of event. The aim of this study was to determine the propensity of specific contact events to cause injury in rugby union. Methods Injury data were reported by medical staff at participating English community level rugby clubs in the 2009/10 (n=46), 2010/11 (n=67), and 2011/12 (n=76) seasons. Injury diagnoses for any injury resulting in an absence from full participation in match
play for one match or more from the day of the injury were recorded using the Orchard Sports Injury Classification System. Injury severity was estimated based on the number of matches missed (accurate to one week / match). Injury data for all seasons were combined for analyses. 30 community rugby matches were filmed and the number of contact events (tackles, collision tackles, rucks, mauls, lineouts and scrums) was recorded using match analysis software (SportsCode Pro, Sportstec, Australia). Significant differences were assumed where 95% confidence intervals (CI) did not overlap. Results There were 370 (95% CI; 364-378) contact events per match of which 141 (137were tackles, 115 (111-119) were rucks and 32 (30-33) were scrums. Tackles resulted in the greatest injury incidence rate [2.3 (2.2-2.4) injuries/1000 events] and severity [16 (15-17) matches missed/1000 events]. Being tackled resulted in a higher incidence rate [1.3 (1.2-1.4) injuries/1000 events] than tackling [1.0 (0.9-1.1) injuries/1000 events]. Collision tackles (illegal tackles involving a shoulder charge) were associated with an incidence rate of 15.0 (12.4-18.3) injuries/1000 events and severity of 83 (68-101) matches missed/1000 events which were higher than any other event. Additional analysis of the scrum in the 2011/12 season showed that collapsed scrums accounted for only 5% of all scrums, but the injury incidence rate was 2.9 (1.5-5.4) injuries/1000 events compared with 0.6 (0.4-0.8) injuries/1000 events for scrums that did not collapse and the severity was 22 (12-42) matches missed/1000 events compared with 3 (2-5) matches missed/1000 events. Discussion Continued focus on injury prevention in the tackle is required through coaching of effective technique when both making tackles and being tackled. In addition, the results support strict enforcement of existing laws in relation to illegal collision tackles. Furthermore, given that the scrum is a relatively controllable phase of contact, further attempts should be made to reduce the frequency of scrum collapses. Acknowledgement Research funded by the Rugby Football Union
THE ANALYSIS OF MOTOR SKILLS, FUNCTIONAL MOVEMENT AND PREVENTION OF INJURY IN ELITE YOUNG SOCCER
PLAYERSZalai, D., Bobák, P., Csaki, I., Hamar, P.
Semmelweis University Introduction Over the course of past few years soccer players have progressed tremendously in terms of physical performance. During a competitive game players frequently perform activities that require rapid development of force such as sprinting and fast change in direction (Sporis, 2011). The increasing demand for players has emphasized the importance of motor skills, quality of functional movements and injury prevention. The purpose of this study was to examine the characteristics and impact of motor skills, functional movements on performance and establish risk factors for injuries among elite young soccer players. Methods The participants (N=60) were tested by Functional Movement ScreenTM (FMS) system, that determined the muscle strength, flexibility, range of motion, coordination, proprioception and identified athletes limitations and functional asymmetries in movement patterns that are considered to be the most significant risk factors for injury (Kiesel, 2007). Findings in motor skills were analyzed further in relation to players position during a game.
Goalkeepers (GK), defenders (DEF), midfielders (MID), and forwards (FW) were investigated regarding their lower limbs explosive strength (LLES) for the horizontal and vertical plane, and the sprint ability (SA) in 5, 10 and 30 meter. Results We have found statistically significant correlations between test LLES (r=0,584) and test SA on 5m and 10m (r=0,797) in relation to players anthropometric parameters (height, 185,4+-5,65cm; weight, 82,8+-6,76kg; BMI, 24,08+-1,27). Findings in DEF showed significant differences concerning sprint ability in 10 and 30 meters (p‹0,05) compare to other groups. The FMS (mean score, 15,47+-1,93) tests have not established substantial link to the anthropometric variables (r=-0,236) and sprint abilities (r=-0,143), but 41% of players examined demonstrated movements asymmetry and limitations. Discussion The observations made by this study emphasize the importance of timely and detailed evaluation and selection of football players at the beginning of their academy training. It has also verified the incidence and type of functional asymmetry in player’s movement patterns. Athletes with lower limb asymmetry have an increased risk to develop non contact injury (Kiesel, 2008). This has also been demonstrated in a previous milestone study by FIFA F-Marc that revealed the non contact nature of injuries in 54% of cases. References Kiesel K, Plisky P, Voight ML. (2007). North Am J Sports Phys Ther., 3, 147-158. Kiesel K, Plisky P, Kersey P. (2008). Med Scie Sports Exerc., 5, 40-48. Sporis G, Milanovic Z, Trajkovic N, Joksimovic A. (2011). Acta Kinesiologica, 5, 36-41.
10:20 - 11:50 Invited symposia IS-PM02 ACSM Exchange symposium: Exercise - Thermoregulation *
HEAT TRANSFER FROM SKIN TO ENVIRONMENT IN HYPERTHERMIC HUMANSHavenith, G.
Loughborough University This second invited presentation of the ECSS-ACSM exchange will look at the heat transfer outside the body, i.e. from the skin outwards, and at recent insights in this process. Starting from the classical heat balance approach, which mostly treats the body as a uniform surface, the presentation will look at regional variation in dry and evaporative heat transfer across the body, linking heat transfer to local body movements, local blood flow and to the local generation of sweat. Body heat loss and sweat production maps produced in the last few years have improved the modelling of heat exposure and have also contributed to the design of sex-specific garments, incorporating the information obtained. Finally the role of clothing and protective gear in this heat transfer will be discussed and the effect they have on heat strain. Promises made be innovative clothing fabrics will be briefly addressed too.
INTERNAL HEAT TRANSFER IN EXERCISING HUMANSKenney, W.
Penn State University The first in a sequence of two presentations, this invited lecture discusses metabolic heat (M) generation and its requisite transfer from working muscle to the skin. M can be extremely high in exercise, sport, and work scenarios due to intensity of effort and inefficiency of external work produced. Adiabatic exercise would limit exercise duration to minutes in most circumstances, illustrating the need for
convective transfer of heat to the skin. Convective heat transfer is a function of (1) specific heat of blood, (2) the core-to-skin temperature gradient, and (3) skin blood flow, and only the latter is physiologically regulated. Active cutaneous vasodilation involves sympathetic cholinergic co-transmitter release. Further, nitric oxide (NO) bioavailability is a downstream requirement for full reflex cutaneous vasodilation. In older exercising subjects, as well as those with vascular dysfunction (hypertension, hypercholesterolemia) NO-mediated dilation is reduced, with the potential consequence of attenuated heat loss.
10:20 - 11:50 Oral presentations OP-PM45 Sports Medicine [SM] 6
PERSISTENCE OF EXERCISE ADAPTATIONS AFTER ONE MONTH OF DETRAINING IN METABOLIC SYNDROME PATIENTSHamouti, N., Ortega, J.F., Fernández-Elías, V.E., Mora-Rodriguez, R.
University of Castilla-La Mancha Introduction: High-intensity aerobic interval training is associated with the removal of some the factors that constitute the metabolic syndrome (MetS) (1). However, it is unclear which of the adaptations are long-term maintained and which are less persistent after exercise training cessation. The STRRIDE study revealed that, after 2 weeks of detraining, the training-induced improvements on insulin sensitivity (2) and HDL-c (3) in sedentary overweight adults persist when exercise is intense enough. To our knowledge, training cessation beyond 2 weeks has not been explored yet in MetS patients. Material and methods: Forty-eight sedentary MetS patients (22 men and 26 women, 52±8.8 yrs old) underwent 16 weeks of 3 days per week of supervised cycle-ergometer high-intensity aerobic interval training (HIAIT).
Training sessions was composed of 4x4 min bouts of pedaling at 90% HRmax interspersed by 3 min at 70% HRmax. MetS factors, blood metabolites, cardio-respiratory (VO2max) and metabolic (maximal fat oxidation, MFO) fitness and insulin resistance (HOMA-IR) were measured when subjects were sedentary and at 48 h and 33 days after the final training bout. Results: Waist circumference was reduced with training (2.4 cm) and remained at trained values after 33 days of detraining. Systolic, diastolic blood pressure and HDL-c improved with 4 months of training (13±3; 12±8% and 12±10% respectively, P0.05) and returned to the 3 months of training values with detraining.
In contrast, the gains in HOMA-IR, VO2max and MFO were almost completely lost after 33 days of detraining. Conclusions: Training improvements on body composition were held after 1 month of detraining. The blood pressure and HDL-c improvements decreased with detraining at a rate of 1 to 1 (i.e., 1 month of detraining, cancels out the last month of training). However, insulin sensitivity and cardiometabolic fitness evaluated during exercise decreased with detraining at a rate of 1 to 3 (i.e., 1month of detraining cancels out 3 months of training). Surprisingly, some important training adaptations that reduce the risk of cardiovascular diseases (i.e., blood pressure and HDL-c) were persistent to 33 days of detraining. 1. Tjonna AE, et al. Aerobic interval training versus continuous moderate exercise as a treatment for the metabolic syndrome: a pilot study. Circulation 118:346-54, 2008. 2. Bajpeyi S, et al. Effect of exercise intensity and volume on persistence of insulin sensitivity during training cessation. J Appl Physiol 106: 1079–1085, 2009. 3. Slentz CA, et al. Inactivity, exercise training and detraining, and plasma lipoproteins. STRRIDE: a randomized, controlled study of exercise intensity and amount. J Appl Physiol 103: 432–442, 2007.
CDC34+ CIRCULATING PROGENITOR CELLS AFTER DIFFERENT TRAINING METHODSNiño, O., Javierre, C., Blasi, J., Balagué, N., Aragonés, D., Corral, L., Miguel, M., Gaitán-Peñas, H., Viscor, G., Ventura, J.L.
Univesity of Barcelona.