Metabolic consequences of exercise-induced muscle damage.

Exercise-induced muscle damage (EIMD) is commonly experienced following either a bout of unaccustomed physical activity or following physical activity of greater than normal duration or intensity. The mechanistic factor responsible for the initiation of EIMD is not known; however, it is hypothesised to be either mechanical or metabolic in nature. The mechanical stress hypothesis states that EIMD is the result of physical stress upon the muscle fibre. In contrast, the metabolic stress model predicts that EIMD is the result of metabolic deficiencies, possibly through the decreased action of Ca(2+)-adenosine triphosphatase. Irrespective of the cause of the damage, EIMD has a number of profound metabolic effects. The most notable metabolic effects of EIMD are decreased insulin sensitivity, prolonged glycogen depletion and an increase in metabolic rate both at rest and during exercise. Based on current knowledge regarding the effects that various types of damaging exercise have on muscle metabolism, a new model for the initiation of EIMD is proposed. This model states that damage initiation may be either metabolic or mechanical, or a combination of both, depending on the mode, intensity and duration of exercise and the training status of the individual

The relationships between rugby players’ tackle training attitudes and behaviour and their match tackle attitudes and behaviour

Background The tackle event in rugby is a technical and physical contest between opposing players. A player's ability to tolerate and contest during a tackle is a prerequisite for safe participation and success in rugby. Little is known about the relationship between tackle training and tackling in matches in rugby union. Therefore, we investigated the relationships between players’ training attitudes and behaviour and their match attitudes and behaviour for tackling in rugby union. Method A questionnaire was designed to assess attitude (importance) and behaviours (frequency and quantity) among junior (under 19) players on a 5-point Likert Scale. Questionnaires were handed out to 220 players (10 schools) at a tournament and 75% (9 schools, n=164) were returned for analysis. Associations between training attitudes and behaviours were tested using the χ2 test, Cramer's V and τ-b. Results The more time spent on emphasising proper technique to prevent injuries in training, the more important players rated ‘own safety’ (τ-b=0.21, moderate, z=3.1, p<0.01), ‘going for the ball only’ (τ-b=0.27, moderate, z=4.6, p<0.001) and ‘staying on feet’ (τ-b=0.23, moderate, z=3.6, p<0.001) in match play. The more time spent on emphasising proper technique to improve performance in training, the more important players rated actions ‘going for ball only’ (τ-b=0.23, moderate, z=3.7, p<0.001) and ‘preventing the ball carrier from retaining position’ (τ-b=0.20, moderate, z=3.1, p<0.01) in match play. Conclusions This is the first study to report on the relationships between players’ training attitudes and behaviour and their match attitudes and behaviours for tackling in rugby union. The importance of tackle training to prevent injury, and the amount of time spent on technique to prevent injuries, was associated with behaviours that reduce the risk of injury in matches

Skills Associated with Line Breaks in Elite Rugby Union

The ability of the attacking team to break through the defensive line is a key indicator of success as it creates opportunities to score tries. The aim of this study was to analyse line breaks and identify the associated skills and playing characteristics. The 2013 Super Rugby season (125 games) was analysed, in which 362 line breaks were identified and coded using variables that assessed team patterns and non-contact attacking skills in the phases preceding the line break. There was an average of 3 line breaks per game, with 39% of line breaks resulting in a try. Line breaks occurred when the ball-carrier was running fast [61%, x 2 (4) = 25.784, p = 0.000, Cramer’s v = 0.1922, weak]. At a moderate distance, short lateral passes (19%) and skip passes (15%) attributed to the highest percentage of line breaks [x 2 (26) = 50.899, p = 0.036, Cramer’s v = 0.2484, moderate]. Faster defensive line speeds resulted in more line breaks [x 2 (12) = 61.703, p < 0.001, Cramer’s v = 0.3026, moderate]. Line breaks are associated with overall team success and try scoring opportunities. Awareness of the defenders line speed and depth, fast running speed when receiving the ball and quick passing between attackers to the outside backs creates line break opportunities. During training, coaches should emphasise the movement speed of the ball between attackers and manipulate the speed and distance of the defenders

Rugby union movement patterns: The impact of fatigue and substitute players

There is currently limited information on the effect of fatigue and the impact of substitutes on movement patterns in rugby union match play. This study investigated the effect of half on movement patterns of whole game players in different positions (backs and forwards), and how these contrast with substitute players. Global positioning system (GPS) data was collected from 105 professional match participations. Relative distance (m.min-1) increased in the second half for whole game players (7 ± 9%), due to an increase in walking distance (1st 29.1 ± 3.9 vs. 2nd 34.2 ± 3.7 m.min-1). High-intensity running distance decreased in the second half for forwards(1st 10.0 ± 5.0 vs. 2nd 8.6 ± 3.8 m.min-1), but increased for backs (1st 10.6 ± 3.2 vs. 2nd 11.4 ± 2.5 m.min-1). Substitutes demonstrated increased relative jogging (Start 19.5 ± 5.0 vs. Sub 23.8 ± 6.3 m.min-1) and striding (Start 7.9 ± 2.4 vs. Sub 10.6 ± 5.5 m.min-1) distance versus whole game players. These findings indicate that fatigue may result in reduced high-intensity running distance and that this effect may be managed through the use of substitutes

Impact of Fatigue on Positional Movements During Professional Rugby Union Match Play.

PURPOSE: In team sports, fatigue is manifested by a self-regulated decrease in movement distance and intensity. There is currently limited information on the effect of fatigue on movement patterns in rugby union match play, particularly for players in different position groups (backs vs. forwards). This study investigated the effect of different match periods on movement patterns of professional rugby union players. METHODS: Global positioning system (GPS) data were collected from 46 professional match participations to determine temporal effects on movement patterns. RESULTS: Total relative distance (m.min-1) was decreased in the 2nd half for both forwards (-13, ±8%; ES = very likely large) and backs (-9, ±7%; ES = very likely large). A larger reduction in high-intensity running distance in the 2nd half was observed for forwards (-27, ±16%; ES = very likely medium) than for backs (-10, ±15%; ES = unclear). Similar patterns were observed for sprint (>6 m.s-1) frequency (forwards -29, ±29%; ES = likely small vs. backs -13, ±18%; ES = possibly small) and acceleration (>2.75 m.s-2) frequency (forwards -27, ±24%; ES = likely medium vs. backs -5, ±46%, ES = unclear). Analysis of 1st and 2nd half quartiles revealed differing pacing strategies for forwards and backs. Forwards display a "slow-positive" pacing strategy, while the pacing strategy of backs is "flat". CONCLUSIONS: Forwards suffered progressively greater performance decrements over the course of the match, while backs were able to maintain performance intensity. These findings reflect differing physical demands, notably contact and running loads, of players in different positions

Functional movement screen predicts severe contact and non-contact injuries in rugby union players

Introduction: Rugby union is a collision sport with a relatively high risk of injury. The ability of the Functional Movement ScreenTM (FMS) to predict the occurrence of severe (≥28 days) contact and non-contact injuries in professional players was assessed. Methods: 90 FMS test observations were compared with severe injuries sustained during 6 subsequent months. Areceiver operated characteristic (ROC) curve determined the FMS score that best predicted severe injury. 2 x 2 contingency tables were used to determine sensitivity, specificity and odds ratios of the prediction. Results: Mean FMS scores were significantly lower in players who sustained severe injury (injured 13.1 ± 1.7 vs. non-injured 14.5 ± 1.4), and severe contact injuries (injured 13.1 ± 2.0 vs. non-injured 14.3 ± 1.5). A receiver-operated characteristic (ROC) curve determined that odds of severe injury, contact injury and non-contact injury were 5.2 (95% CI = 2.0-13.9), 6.5 (95%CI = 1.8 to 23.0) and 4.3 (95%CI = 0.9 to 21.0) times greater respectively if FMS score was below the relevant cut-off score. Low active straight leg raise score (≤ 2) was also significantly associated with injury. Players were divided into High-FMS (≥14) and Low-FMS (≤ 13) groups to estimate the potential effect of low FMS scores. Survival analysis showed a greater fractional survival rate for High-FMS group (≥14) versus a Low-FMS group (≤ 13) (81.4% 95%CI = 68.9 to 89.2% vs. 50.0% 95%CI = 31.3 to 68.7, p<0.05). The Low-FMS group spent more days injured (47 ± 47 vs. 25 ± 39 days) and took longer to recover (29 ± 38 vs. 10 ± 16 days) than the HighFMS group. Conclusion: These findings indicate that FMS score is a risk factor for severe contact and non-contact injury in professional rugby players

Movement, impact and pacing characteristics of South African professional rugby players

Introduction: Global positioning system (GPS) technology provides accurate, real-time movement pattern analysis. GPS will improve understanding of the movement characteristics of players during professional rugby union matchplay. Methods: 19 Professional rugby players were tracked using GPS during 24 matches during the 2013 rugby season. Players were grouped as (1) backs or forwards and (2) tight forwards, loose forwards, scrumhalves, inside backs or outside backs. Movements were categorized as walking (0-2m.s-1), jogging (2-4m.s-1), striding (4-6m.s-1) and sprinting (>6m.s-1). Walking and jogging were classified as low intensity and striding and sprinting as high intensity movement zones. An inbuilt tri-axial accelerometer quantified impacts. Pacing effects were determined by comparing 1st and 2nd half movement patterns and whole game players to substitutes. Results: There was no difference between forwards and backs in relative distance covered or impact variables. Backs reached higher maximum speeds than forwards (Backs 8.8 ± 1.1 vs. Forwards 7.6 ± 1.3 m.s-1, ES = 1.0), and covered more distance than forwards in high intensity speed zones (forwards 10 ± 5 vs. backs 12 ± 4 m.min-1, ES = 0.6). Outside backs were the fastest positional group (9.4 ± 0.9 m.s-1, ES = 0.4-2.2), while tight forwards covered the most distance in low intensity zones (57 ± 5m.min-1, ES = 0.4–1.8) Loose forwards and inside backs exhibited similar movement patterns. Relative distance (m.min-1) increased in the second half for whole game players (7 &p lusmn; 9%). High-intensity running distance decreased in the second half for forwards (1st 10.0 ± 5.0 vs. 2nd 8.6 ± 3.8 m.min-1), but increased for backs (1st 10.6 ± 3.2 vs. 2nd 11.4 ± 2.5 m.min-1). Substitutes demonstrated increased relative jogging (Start 20 ± 5 vs. Sub 24 ± 6 m.min-1) and striding (Start 8 ± 2 vs. Sub 11 ± 6 m.min-1) distance versus whole game players. Conclusions: There are notable differences in the movement of professional rugby union players in different positions. Fatigue results in reduced high-intensity running distance and this effect can be managed through the use of substitutes

Toxic metal enrichment and boating intensity: sediment records of antifoulant copper in shallow lakes of eastern England

Tributyltin (TBT), an aqueous biocide derived from antifouling paint pollution, is known to have impacted coastal marine ecosystems, and has been reported in the sediment of the Norfolk and Suffolk Broads, a network of rivers and shallow lakes in eastern England. In the marine environment, the 1987 TBT ban has resulted in expanded use of alternative biocides, raising the question of whether these products too have impacted the Broads ecosystem and freshwaters in general. Here we examine the lake sediment record in the Norfolk and Suffolk Broads for contamination by copper (Cu) (as an active biocide agent) and zinc (Zn) (as a component of booster biocides), to assess their occurrence and potential for causing environmental harm in freshwater ecosystems. We find that, after the introduction of leisure boating, there is a statistically significant difference in Cu enrichment between heavily and lightly boated sites, while no such difference exists prior to this time. At the heavily boated sites the onset of Cu enrichment coincides with a period of rapid increase in leisure boating. Such enrichment is maintained to the present day, with some evidence of continued increase. We conclude that Cu-based antifouling has measurably contaminated lakes exposed to boating, at concentrations high enough to cause ecological harm. Similar findings can be expected at other boated freshwater ecosystems elsewhere in the world

HIRDLS poster

A poster supporting the HIRDLS data held at the BADC (High Resolution Dynamics Limb Sounder (HIRDLS) instrument)

Observation of interstellar lithium in the low-metallicity Small Magellanic Cloud

The primordial abundances of light elements produced in the standard theory of Big Bang nucleosynthesis (BBN) depend only on the cosmic ratio of baryons to photons, a quantity inferred from observations of the microwave background. The predicted primordial 7Li abundance is four times that measured in the atmospheres of Galactic halo stars. This discrepancy could be caused by modification of surface lithium abundances during the stars' lifetimes or by physics beyond the Standard Model that affects early nucleosynthesis. The lithium abundance of low-metallicity gas provides an alternative constraint on the primordial abundance and cosmic evolution of lithium that is not susceptible to the in situ modifications that may affect stellar atmospheres. Here we report observations of interstellar 7Li in the low-metallicity gas of the Small Magellanic Cloud, a nearby galaxy with a quarter the Sun's metallicity. The present-day 7Li abundance of the Small Magellanic Cloud is nearly equal to the BBN predictions, severely constraining the amount of possible subsequent enrichment of the gas by stellar and cosmic-ray nucleosynthesis. Our measurements can be reconciled with standard BBN with an extremely fine-tuned depletion of stellar Li with metallicity. They are also consistent with non-standard BBN.Comment: Published in Nature. Includes main text and Supplementary Information. Replaced with final title and abstrac