The effect of low back pain on trunk muscle size/function and hip strength in elite football (soccer) players

ABSTRACT

Low back pain (LBP) is a common problem in football (soccer) players. The effect of LBP on the trunk and hip muscles in this group is unknown. The relationship between LBP and trunk muscle size and function in football players across the preseason was examined. A secondary aim was to assess hip muscle strength. Twenty-five elite soccer players participated in the study, with assessments conducted on 23 players at both the start and end of the preseason. LBP was assessed with questionnaires and ultrasound imaging was used to assess size and function of trunk muscles at the start and end of preseason. Dynamometry was used to assess hip muscle strength at the start of the preseason. At the start of the preseason, 28% of players reported the presence of LBP and this was associated with reduced size of the multifidus, increased contraction of the transversus abdominis and multifidus muscles. LBP decreased across the preseason, and size of the multifidus muscle improved over the preseason. Ability to contract the abdominal and multifidus muscles did not alter across the preseason. Asymmetry in hip adductor and abductor muscle strength was found between players with and without LBP. Identifying modifiable factors in players with LBP may allow development of more targeted preseason rehabilitation programmes.     

An examination of the jump-and-lift factors influencing the time to reach peak catch height during a Rugby Union lineout

The goal of an offensive Rugby Union lineout is to throw the ball in a manner that allows your team to maintain possession. Typically, the player catching the ball jumps and is lifted upwards by two teammates, reaching above the opposing player who is competing for the ball also. Despite various beliefs regarding the importance of the jumper’s mass and attempted jump height, and lifters’ magnitude and point of force application, there is negligible published data on the topic. The squeeze technique is one lifting method commonly employed by New Zealand teams during lineout plays, whereby the jumper initiates the jump quickly and the lifters provide assistance only once the jumper reaches 20–30 cm. While this strategy may reduce cues to the opposition, it might also constrain the jumper and lifters. We developed a model to explore how changes in the jumper’s body mass and attempted jump height, and lifters’ magnitude and point of force application influence the time to reach peak catch height. The magnitude of the lift force impacted the time-to-reach peak catch height the most; followed by the jumper’s (attempted) jump height and body mass; and lastly, the point of lift force application.     

From the Margins to the Mainstream: Potential Impact of Early Colleges on Traditional High Schools

Early colleges are one alternative to the traditional comprehensive high school. This article describes the establishment of an early college in partnership with a university, including the experiences for students, the challenges for teachers, and the difficulties in bridging higher and kindergarten through Grade-12 educations. The article considers the potential for these new, small high schools to impact the traditional high school.     

A review of models of vertical,leg, and knee stiffness in adults for running,jumping or hopping tasks

Abstract

The ‘stiffness’ concept originates from Hooke's law which states that the force required to deform an object is related to a spring constant and the distance that object is deformed. Research into stiffness in the human body is undergoing unprecedented popularity; possibly because stiffness has been associated with sporting performance and some lower limb injuries. However, some inconsistencies surrounding stiffness measurement exists bringing into question the integrity of some research related to stiffness. The aim of this study was to review literature which describes how vertical, leg and knee stiffness has been measured in adult populations while running, jumping or hopping. A search of the entire MEDLINE, PubMed and SPORTDiscus databases and an iterative reference check was performed. Sixty-seven articles were retrieved; 21 measured vertical stiffness, 51 measured leg stiffness, and 22 measured knee stiffness. Thus, some studies measured several ‘types’ of stiffness. Vertical stiffness was typically the quotient of ground reaction force and centre of mass displacement. For leg stiffness it was and change in leg length, and for the knee it was the quotient of knee joint moments and change in joint angle. Sample size issues and measurement techniques were identified as limitations to current research.     

Reproducibility of the maximum accumulated oxygen deficit and run time to exhaustion during short-distance running

The aim of this study was to determine the reproducibility of the maximal accumulated oxygen deficit and the associated exercise time to exhaustion during short-distance running. Fifteen well-trained males (mean +/- s: VO2max = 58.0+/-4.6 ml x kg(-1) x min(-1)) performed the maximum accumulated oxygen deficit test at an exercise intensity equivalent to 125% VO2max. The test was repeated at the same time of day on three occasions within 3 weeks. There was no significant systematic bias between trials for either maximum accumulated oxygen deficit (man +/- s: trial 1 = 69.0+/-13.1; trial 2 = 71.4+/-12.5; trial 3 = 70.4+/-15.0 ml O2 Eq x kg(-1); ANOVA, F = 0.70, PP= 0.51) or exercise time to exhaustion (trial 1 = 194 + 31.1; trial 2 = 198 + 33.2; trial 3 = 201 + 36.8 s; F= 1.49, P = 0.24). In addition, other traditional measures of reliability were also favourable. These included intraclass correlation coefficients of 0.91 and 0.87, and sample coefficients of variation of 6.8% and 5.0%, for maximum accumulated oxygen deficit and exercise time to exhaustion respectively. However, the '95% limits of agreement' were 0+/-15.1 ml O2 Eq (1.01 multiply/divide 1.26 as a ratio) and 0+/-33.5 s (1.0 multiply/divide 1.18 as a ratio) for maximum accumulated oxygen deficit and exercise time to exhaustion respectively. We estimate that the sample sizes required to detect a 10% change in exercise time to exhaustion and maximum accumulated oxygen deficit after a repeated measures experiment are 10 and 20 respectively. Unlike the results of previous maximum accumulated oxygen deficit studies, we conclude that it is not a reliable measure.     

The stroke has only a minor influence on direction consistency in golf putting among elite players

In the golf instructional literature, the putting stroke is typically given higher priority than green reading and aiming. The main purpose of this study was to assess the importance of the putting stroke for direction consistency in golf putting. Kinematic stroke parameters were recorded from 71 elite golf players (mean handicap = 1.8, s = 4.2) on 1301 putts from about 4 m. Of the different factors deciding stroke direction consistency, face angle was found to be the most important (80%), followed by putter path (17%) and impact point (3%). This suggests that improvements in consistency of putter path and impact point will have very little effect on overall putting direction consistency and should not be prioritized in the training of elite players. In addition, mean stroke direction variability for an elite player (European Tour) was found to be 0.39 degrees, which is good enough to hole about 95% of all 4-m putts. In practice, however, top professionals in tournaments only hole about 17% of 4-m putts. We conclude that the putting stroke of elite golfers has a relatively minor influence on direction consistency.     

The effects of an increasing versus constant crank rate on peak physiological responses during incremental arm crank ergometry

We examined the effects of concomitant increases in crank rate and power output on incremental arm crank ergometry. Ten healthy males undertook three incremental upper body exercise tests to volitional exhaustion. The first test determined peak minute power. The subsequent tests involved arm cranking at an initial workload of 40% peak minute power with further increases of 10% peak minute power every 2 min. One involved a constant crank rate of 70 rev · min(-1), the other an initial crank rate of 50 rev · min(-1) increasing by 10 rev · min(-1) every 2 min. Fingertip capillary blood samples were analysed for blood lactate at rest and exhaustion. Local (working muscles) and cardiorespiratory ratings of perceived exertion (RPE) were recorded at the end of each exercise stage. Heart rate and expired gas were monitored continuously. No differences were observed in peak physiological responses or peak minute power achieved during either protocol. Blood lactate concentration tended to be greater for the constant crank rate protocol (P = 0.06). Test duration was shorter for the increasing than for the constant crank rate protocol. The relationship between local RPE and heart rate differed between tests. The results of this study show that increasing cadence during incremental arm crank ergometry provides a valid assessment of peak responses over a shorter duration but alters the heart rate-local RPE relationship.