The influence of a intense training program on hypermobility and correlation between hypermobility and incidence of injury

Abstract

Joint hypermobility (JH) in its various forms is in many ways misinterpreted and underdiagnosed. As a symptom of heritable disorders of connective tissue (HDCT), it is well known, whilst understanding around JH as a non-symptomatic occurrence in physically active populations is vague at best. With literature suggesting associations between JH and musculoskeletal injury (MSI), an inherent risk for populations undergoing intense physical training (PT) is implied. This dissertation set out to shed light on the incidence of hypermobility in a South African context, whilst seeking to clarify the implications of JH on intense PT and vice versa. The research was conducted by employing an in depth literature review on the broad spectrum of physiological factors linked to hypermobility, along with three comprehensive scientific studies which answered definitive questions relating to the paper s main research objectives. In investigating the causative factors of JH, literature indicated congenital amino-acid substitutions in collagen synthesis which compromises the molecular nano-mechanics of connective tissues, thus negating the structural integrity of collagen containing compounds such as tendons, ligaments, joint capsules, skin, demineralised bone and nerve receptors. This concept, along with current thinking which suggests that the shape of bones and low muscle tone may also contribute to hypermobility, clearly indicates compromised joint biomechanics in hypermobile individuals. A commonly linked neurologic factor of hypermobility i.e. diminished joint proprioceptive acuity, lead to our proposed concept of a closed cycle of causative vs. symptomatic factors, which perpetuates abnormal articular biomechanics. The initial study which sought to investigate the incidence rates of hypermobility in the general South African population, employed a cross-sectional research approach with a sample population of 480 individuals from four wide-spread geographical areas. Individuals were tested for JH according to the Beighton nine-point hypermobility score with a diagnostic criteria of 4/9 or greater. Results indicated a 26.19% overall incidence of JH, with sex specific totals showing a 36.41% incidence for females compared to 13.96% for males. Thus concurring with contemporary studies indicating a significantly high prevalence of JH in the general population. The second study which concerned the interactions between muscular component and hypermobility, correlated Beighton nine-point hypermobility scores and lean body mass (LBM) at three intervals during a 20 week intense training intervention period in a military sample. Linear regressions indicated a significant correlation between increased LBM and associated decreases in hypermobility, even though hypermobility peaked after 12 weeks of intense exercise. We proposed that the hypermobility peak leading up to week 12 can be clarified by initial training induced generalized flexibility, neural adaptation of exercise which increases ROM amongst other factors. In aiming to clarify one of the most prevalent discussions in hypermobility research i.e. the association between JH and MSI, the final study compared MSI incidences between hypermobile and non-hypermobile individuals who endured 20 weeks of intense military basic training protocols. Odds ratios indicated that hypermobile individuals are 1.8 times more likely to sustain MSI when undergoing intense physical activity. Chi-square tests indicated a marginal, though significant association between JH and MSI. Ulterior results showed increased MSI prevalence amongst females as well as no significant difference in MSI location distribution amongst the hypermobile and control groups. In considering all our findings we concluded that JH is an underdiagnosed common occurrence in the South African general population. The congenital influences on connective tissue development in hypermobile individuals sufficiently undermines musculoskeletal integrity to the extent where they are susceptible to increased risk of injury when participating in intense physical activity. These debilitating mechanisms can however be counteracted by the implementation of specific exercises promoting joint stabilization, proprioceptive acuity and increased muscular component.