AUTUMN 2011, VOLUME 4 ISSUE 1
In this issue:
Understanding the causes, prevention and treatment of osteoporosis (part 1): the structure of bone and the remodelling process, Anthropometric and fitness development of British elite female basketball players: from grassroots to high level, The impact of playing position and level on the fitness characteristics of female soccer players, Acute effects of dynamic and static stretching on vertical jump performance, Effects of vibration on disease activity scores in a patient with rheumatoid arthritis: a case study, Biomechanical analysis of a single-limb flat squat versus a single-limb decline squat: implications for ACL injury prevention, The reliability and validity of the reactive agility t-test.
The effects of playing position and level on performance in a battery of fitness tests…
Football can be classified as an aerobic or endurance sport encompassing short periods of intense anaerobic activity throughout the ninety minutes of a game. The demands placed on a player during a game therefore require them to be proficient in a range of fitness components such as aerobic and anaerobic power, speed and agility, and a these demands may vary between different playing positions and levels. The purpose of the current study was to examine the effect of playing position and level on the fitness levels of female soccer players.
Understanding the causes, prevention, and treatment of osteoporosis (part 1)...
Osseous tissue, or bone, is a living tissue, composed of a mixture of organic and non-organic substances. Bone tissue can be described according to its level of structure: macro-, micro-, sub-micro-, nano-, and sub-nano-. At the macroscopic level, bone can be classified as cortical or cancellous, organised microscopically as osteons and trabeculae respectively. At the sub-microstructure level bone can be lamellar or non-lamellar, while at the cellular level, bone consists principally of three main cell types: osteoclasts, osteoblasts, and osteocytes, which interact to continuously regenerate the bone matrix. Bone is continuously modelling/remodelling itself throughout an individual’s life, allowing the skeleton to increase in size during growth, respond to physical stresses, and repair structural damage due to fatigue, failure or trauma. Bone homeostasis is only maintained if the processes of resorption and formation are closely coupled. Understanding the micro- and macro-architecture of bone and the processes involved in bone remodelling are crucial in the diagnosis of osteoporosis and the evaluation of the effectiveness of treatments and interventions. The purpose of this article (the first of a three-part feature) is, therefore, to describe the structure and function of bone, the cells involved in bone remodelling, and the process of remodelling itself.
The reliability and validity of the reactive agility t-test
There is currently no ‘gold standard’ for testing agility, and a variety of tests are reported in the literature. Until recently, most tests of agility required participants to complete planned movements, or closed skills, and did not require a response to a stimulus. The purpose of the current study, therefore, was to evaluate the reliability and validity of a field-based test of reactive agility that incorporated both multiple changes of direction and an unpredictable stimulus, which could be easily replicated by the general coaching community. Eighteen soccer players from the USA National Collegiate Athletic Association (NCAA) Division 1 completed two testing sessions, one week apart. The first testing session required the participants to complete three tests; the Reactive Agility T Test (RATT), the Planned Agility T Test (PATT) and a 30m linear sprint test. The second testing session required the participants to complete the RATT. At test 1, the mean planned agility score (5.82s ± 0.17s) was significantly faster (p < 0.01) than the mean reactive agility score (6.11s ± 0.19s).
Biomechanical analysis of a single-limb flat squat versus a single-limb decline squat…
The motions of hip internal rotation, adduction, and knee valgus have been reported to increase strain on the anterior cruciate ligament in the female athlete. While strengthening programs attempt to eliminate these at risk motions, exercises are often performed by the athlete at the expense of poor body mechanics thus mitigating their effectiveness. The aim of the current study was to ascertain whether better control of hip internal rotation and subsequent knee valgus is facilitated when performing a single leg squat on a decline board as compared to a single leg squat on a level surface. Twenty (n=20) healthy active females between the ages of 18-25 years old were participants for this study. Hip and knee muscle strength was collected on Day 1. On Day 2, participants performed five single limb squats on flat ground and five single leg squats on a 25° decline board while joint angle and force data were collected.
Acute effects of dynamic stretching and static stretching on vertical jump performance
Static stretching (SS), as an effective means of injury prevention, has recently come under scrutiny, with dynamic stretching (DS) seemingly appearing to be slowly replacing it in warm up protocols. The purpose of this study was to investigate the acute effects of DS and SS on power output measured by vertical jump performance (VJP) using a force plate. Thirty recreational athletes, 16 female (height = 1.74 ± 0.08m, mass = 72 ± 7kg, Age = 21 ± 1yrs) and 14 male (height = 1.8 ± 0.07m, mass = 89 ± 20kg, age = 21 ± 1yrs) completed the DS, SS or control protocol with pre-testing and post-testing of their VJP. DS and SS interventions were used in accordance with the American College of Sports Medicine (ACSM) guidelines. Despite an 11% decrement in VJP pre- (0.37±0.1m) and post- (0.33±0.08m) SS, this was not significant (p>0.05). Similarly, despite a >14% increase in VJP pre- (0.32±0.07) and post- (0.36±0.06) DS this was also not significant (p>0.05). The control group also experienced a small, but non-significant (p>0.05), increase in VJP of 2.83% from pre- (0.36±0.06) to post- (0.37±0.06) measures, attributable to normal fluctuations in performance. There were no significant changes in VJP and nothing could be directly inferred from these results as the range of VJP scores was very large. The large VJP range raises issue of the muscles sensitivity to stretching and was postulated as a possible contributor to mixed results throughout the literature.
Anthropometric and fitness development of British elite female basketball players…
Basketball is one of the most practised sports in the world. There is a large amount of articles analysing and studying the basketball player’s anthropometry, the basketball parameters, the physiological demands, and the fitness level of the team. However, the vast majority of these studies have focused on male basketball, as opposed to female. There are only a few studies working on British high level female basketball teams. To compare and evaluate the body composition and fitness characteristics of British female basketball players from grassroots to high level against the studies which are available in the literature. Seventy eight (n = 78) female basketball players from the English Basketball League and the Great Britain National Team participated in the current study. The anthropometry tests were: weight, height, arm span, and BMI; and the fitness tests were: Flexibility (sit and reach), Agility (4x10-meter shuttle run), Lower Body Power (Standing Broad Jump), and 20-meter shuttle run Tests. Statistical differences were found between groups in the Agility and Standing Broad Jump Tests. Cardiorespiratory fitness showed a slight tendency to improve as the team’s level increased, although statistical differences were not observed. British female basketball players had fitness level and body composition values lower than high-level female basketball teams from countries where basketball is more popular and better developed. The S&C coach role within the technical staff is necessary and highly recommended to achieve high level competition.
Editorial: Adding ‘weight’ to the argument
French may be regarded by many as the language of love, but few may realise it can also be considered the language of science. Le Système International d’Unités, or the International System of Units (SI), was established in 1960 by the 11th General Conference on Weights and Measures (CGPM, Conférence Générale des Poids et Mesures). The CGPM, created by a diplomatic treaty called the Metre Convention signed in Paris in 1875, ensures wide dissemination and modification of the SI as necessary to reflect the latest advances in science and technology. The SI units consists of units of measurement devised around a number of base units (Table 1) While the physical and life sciences fully embrace this system, other related professions have been slower to fully appreciate it. Even in the clinical setting, using incorrect units to describe quantities is rife: how many of you have equipment, programs, or forms, which require you to enter weight in kilograms or height in centimetres? Using the SI units system, weight is reported in Newton’s (N) based on the formula: force (weight) = mass x acceleration (F=ma), while mass (kg) refers to the amount of matter contained in an object or being. An ‘out of this world’ example clearly illustrates the fundamental difference: a person with a mass of 80kg would weigh ~785N (F=ma [80kg x 9.81m.s-2]) on earth. If this person were on Mars, for example, their mass would remain the same but their weight would now be ~296N (80kg x 3.7-2).
Effects of vibration on disease activity scores and range of motion…
Rheumatoid arthritis (RA) is a disabling disease characterised by chronic inflammation. Moderate to high intensity exercise is recommended for the management of RA, although this is not always achievable due to pain caused by local inflammation. Identifying the current status of the swollen, tender joints and the patient’s perception of pain can be assessed using the ‘disease activity score’ (DAS28). Recently, vibration training has been shown to improve performance within healthy individuals, but has yet to be used in the treatment of RA. One female patient (age: 43yrs; height: 1.53m; mass: 48kg) with active RA was recruited for the current study.