To assess factors that limit human muscle strength and growth, we examined the relationship between performance and body dimensions in the world weightlifting champions of 1993-1997. Weight lifted varied almost exactly with height squared (Ht(2.16)), suggesting that muscle mass scaled almost exactly with height cubed (Ht(3.16)) and that muscle cross-sectional area was closely correlated with body height, possibly because height and the numbers of muscle fibers in cross section are determined by a common factor during maturation. Further height limitations of muscle strength were shown by only one male champion >/=183 cm and no female champions >/=175 cm. The ratio of weight lifted to mean body cross-sectional area was approximately constant for body-weight classes =83 kg for men and =64 kg for women and decreased abruptly for higher weight classes. These findings suggest a nearly constant fraction of body mass devoted to muscle in lighter lifters and a lesser fraction in heavier lifters. Analysis also suggests that contractile tissue comprises approximately 30% less body mass in female champions.
Objectives: To determine if sleep interventions improve pain and sleep in people with osteoarthritis (OA) and/or spinal pain compared to control/placebo. Design: Medline, Embase, AMED, PsycINFO, CENTRAL, CINAHL and PEDro were searched from their inception date to July 2017. Keywords relating to "sleep", "OA", "spinal pain", and "randomized controlled trial (RCT)" were combined. Included RCTs investigated the use of sleep interventions for people with OA and/or spinal pain, and measured at least one sleep and health related outcome. Meta-analyses were performed to pool mean differences for pain and sleep quality. PROSPERO: CRD42016036315. Results: Of 1445 unique records, 24 studies were included. Sixteen studies included participants with spinal pain, seven with OA, and one included a mixed population. Sleep interventions included established sleep interventions (ESI) [cognitive behavioural therapy (CBT) and pharmacological interventions], and a range of others. Intervention periods ranged from 4 to 10 weeks. Thirteen studies were of moderate to high quality (PEDro ! 6/10). Due to high heterogeneity between studies we also performed subgroup and sensitivity analyses. ESI decreased Insomnia Severity Index (ISI) for people with low back pain (LBP) (pooled mean difference: À6.78/28, 95% confidence interval (95% CI): [À9.47, À4.09], I 2 ¼ 40%) and OA (À2.41, [À4.19, À0.63], 0%). However ESI decreased pain for people with LBP (pooled mean difference: visual analogue scale (VAS) À12.77/100, 95% CI: [À17.57, À7.97], I 2 ¼ 0%), but not OA (À2.32, [À7.18, 2.54], 27%). Conclusion: ESI appeared to improve sleep and pain for people with LBP, and sleep for people with OA. However more vigorous studies need to be conducted.
Background and aims Chronic low back pain (chronic LBP) is the number one cause for years lived with disability among 301 diseases and injuries analyzed by The Global Burden of Disease study 2013. Insomnia is highly prevalent among people with chronic LBP. To explain the sleep-pain relationship, theoretical models propose that insomnia symptoms may be associated with increased basal inflammation, operationalized as c-reactive protein (CRP) and lead to further pain and disrupted sleep. We aimed to determine the associations between insomnia, chronic LBP, and inflammation (operationalized as CRP), whilst controlling for age, body mass index, smoking, physical activity, depression, anxiety and osteoarthritis. Methods A cross-sectional analysis of the third Nord-Trøndelag Health Study (2006–2008), a rural population survey of 50,666 participants in Norway aged 20–96 years. Insomnia (dichotomous) was defined according to the Diagnostic and Statistical Manual of Mental Disorders 5th Edition, and chronic LBP (dichotomous) as low back pain or stiffness lasting at least 3 months. Data for CRP were obtained from non-fasting serum samples and assessed via latex immunoassay methodology. We excluded participants with the following self-reported chronic somatic diseases: chronic heart failure, chronic obstructive pulmonary disease, rheumatoid arthritis, fibromyalgia or ankylosing spondylosis. Possible associations between presence of insomnia and presence of chronic LBP (dependent), and the level of CRP and presence of chronic LBP (dependent), were assessed using logistic regression models. The possible association between insomnia and CRP (dependent) was assessed using linear regression. Multivariable analyses were conducted adjusting for confounders stated in our aim that achieved p ≤ 0.2 in univariate regressions. We performed stratified analyses for participants with “Normal” (<3 mg/L) “Elevated” (3–10 mg/L) and “Very High” (>10 mg/L) levels of CRP. Results In our total included sample (n = 30,669, median age 52.6, 54% female), 6.1% had insomnia (n = 1,871), 21.4% had chronic LBP (n = 6,559), and 2.4% had both (n = 719). Twenty four thousand two hundred eighty-eight (79%) participants had “Normal” CRP, 5,275 (17%) had “Elevated” CRP, and 1,136 (4%) had “Very High” CRP. For participants with “Normal” levels of CRP, insomnia was associated with higher levels of CRP (adjusted B = 0.04, 95%CI [0.00–0.08], p = 0.046), but not for people with “Elevated” or “Very High” levels of CRP. There was an association between CRP and presence of chronic LBP in the total sample (adjusted OR = 1.01, [1.00–1.01], p = 0.013) and for people with “Normal” CRP (1.05, [1.00–1.10, p = 0.034]. Insomnia was associated with the presence of chronic LBP in the total sample (adjusted OR = 1.99, 95%CI [1.79–2.21], <0.001) and for people with “Normal”, “Elevated” and “Very High”. Conclusions Individuals with insomnia have twice the odds of reporting chronic LBP. Insomnia, CRP and chronic LBP appear to be linked but the role of CRP appears to be limited. Longitudinal studies may help further explore the causal inference between insomnia chronic LBP, and inflammation. Implications Given the strong relationship between insomnia and chronic LBP, screening and management of comorbid insomnia and chronic LBP should be considered in clinical practice. Further longitudinal studies are required to explore whether the presence of insomnia and increased inflammation affects the development of chronic LBP.
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