Last updated on 11th May 2019
Poor muscle strength predicts increased vulnerability to both physical & psychological health problems and earlier death, in addition to the contribution of poor aerobic, heart-lung fitness. This is true for both men & women and for all assessed age ranges. Mechanisms underlying these effects are probably multifactorial, including metabolic/biochemical, neurological & psychological factors. Research studies have assessed overall muscular strength in a variety of ways including grip strength, push-ups, chair-stands, and squat weight-lifts. Happily, muscle strengthening interventions can yield major benefits across multiple health domains. Here are a dozen interesting papers addressing these areas published in the last few years:
"Prognostic value of grip strength: findings from the Prospective Urban Rural Epidemiology (PURE) study." (2015) This huge study across 17 countries found that, in 35 to 70 year olds "grip strength was a stronger predictor of all-cause and cardiovascular mortality than systolic blood pressure" and that, for both men & women "During a median follow-up of 4·0 years ... 3379 (2%) of 139 691 participants died. After adjustment, the association between grip strength and each outcome, with the exceptions of cancer and hospital admission due to respiratory illness, was similar across country-income strata. Grip strength was inversely associated with all-cause mortality (hazard ratio per 5 kg reduction in grip strength 1·16, p<0.0001)."
"Independent and joint associations of grip strength and adiposity with all-cause and cardiovascular disease mortality in 403,199 adults: the UK Biobank study." (2017) This research on 40 to 69 year olds demonstrated "Over a median 7.0-y of follow-up, 8287 all-cause deaths occurred. The highest GS (grip strength) quintile had 32% ... and 25% ... lower all-cause mortality risks for men and women, respectively, compared with the lowest GS quintile, after adjustment for confounders and BMI."
"Muscular strength in male adolescents and premature death: cohort study of one million participants." (2012) "Baseline examinations included knee extension, handgrip, and elbow flexion strength tests, as well as measures of diastolic and systolic blood pressure and body mass index. Cox regression was used to estimate hazard ratios for mortality according to muscular strength categories (tenths). RESULTS: During a median follow-up period of 24 years, 26 145 participants died. Suicide was a more frequent cause of death in young adulthood (22.3%) than was cardiovascular diseases (7.8%) or cancer (14.9%). High muscular strength in adolescence, as assessed by knee extension and handgrip tests, was associated with a 20-35% lower risk of premature mortality due to any cause or cardiovascular disease, independently of body mass index or blood pressure; no association was observed with mortality due to cancer. Stronger adolescents had a 20-30% lower risk of death from suicide and were 15-65% less likely to have any psychiatric diagnosis (such as schizophrenia and mood disorders)."
"The physical capability of community-based men and women from a British cohort: the European Prospective Investigation into Cancer (EPIC)-Norfolk study." (2013) This large scale study found about 1 in 3 women and about 1 in 4 men over age 65 were concerningly physically weak (here 'defined' as grip strength less than 20kg in women & 30kg in men). On average, grip strength declined by 0.49kg per year in men and 0.25kg per year in women.
"Strength training and the risk of Type 2 diabetes and cardiovascular disease." (2017) "We followed 35,754 healthy women ... from the Women's Health Study, who responded to a health questionnaire that included physical activity questions in 2000, assessing health outcomes through annual health questionnaire through 2014. Cases of cardiovascular disease were defined as confirmed cases of myocardial infarction, stroke, coronary artery bypass graft, angioplasty, or cardiovascular disease death. RESULTS: Compared with women who reported no strength training, women engaging in any strength training experienced a reduced rate of type 2 diabetes of 30% ... when controlling for time spent in other activities and other confounders. A risk reduction of 17% was observed for cardiovascular disease among women engaging in strength training ... Participation in both strength training and aerobic activity was associated with additional risk reductions for both type 2 diabetes and cardiovascular disease compared with participation in aerobic activity only."
"Handgrip strength and depression among 34,129 adults aged 50 years and older in six low- and middle-income countries." (2019) "Introduction Handgrip strength is a simple and inexpensive marker of health and mortality risk. It presents an ideal risk-stratifying method for use in low and middle-income countries (LMICs). There are, however, no population-based studies investigating the associations between handgrip strength and depression in LMICs ... Method Cross-sectional data on individuals aged ≥ 50 years from the World Health Organization's Study on Global Ageing and Adult Health were analyzed ... Weak handgrip strength was defined as < 30 kg for men and < 20 kg for women using the average value of two handgrip measurements of the dominant hand ... Results The sample included 34,129 individuals (62.4 ± 16.0 years; 52.1% female). The prevalence of weak handgrip strength and depression were 47.4% and 6.2%, respectively ... Across all countries, after adjustment for potential confounders, weak handgrip strength was associated with a 1.45 times higher odds for depression. Discussion Weaker handgrip strength is associated with higher odds for depression in LMICs."
"Association of efficacy of resistance exercise training with depressive symptoms: Meta-analysis and meta-regression analysis of randomized clinical trials." (2018) Importance The physical benefits of resistance exercise training (RET) are well documented, but less is known regarding the association of RET with mental health outcomes. To date, no quantitative synthesis of the antidepressant effects of RET has been conducted. Objectives To estimate the association of efficacy of RET with depressive symptoms and determine the extent to which logical, theoretical, and/or prior empirical variables are associated with depressive symptoms and whether the association of efficacy of RET with depressive symptoms accounts for variability in the overall effect size. Data Sources Articles published before August 2017, located using Google Scholar, MEDLINE, PsycINFO, PubMed, and Web of Science.Study Selection Randomized clinical trials included randomization to RET (n = 947) or a nonactive control condition (n = 930).Data Extraction and Synthesis Hedges d effect sizes were computed and random-effects models were used for all analyses. Meta-regression was conducted to quantify the potential moderating influence of participant and trial characteristics. Main Outcomes and Measures Randomized clinical trials used validated measures of depressive symptoms assessed at baseline and midintervention and/or postintervention. Four primary moderators were selected a priori to provide focused research hypotheses about variation in effect size: total volume of prescribed RET, whether participants were healthy or physically or mentally ill, whether or not allocation and/or assessment were blinded, and whether or not the RET intervention resulted in a significant improvement in strength. Results Fifty-four effects were derived from 33 randomized clinical trials involving 1877 participants. Resistance exercise training was associated with a significant reduction in depressive symptoms with a moderate-sized mean effect ∆ of 0.66 (95% CI, 0.48-0.83; z = 7.35; P < .001). Significant heterogeneity was indicated (total Q = 216.92, df = 53; P < .001; I2 = 76.0% [95% CI, 72.7%-79.0%]), and sampling error accounted for 32.9% of observed variance. The number needed to treat was 4. Total volume of prescribed RET, participant health status, and strength improvements were not significantly associated with the antidepressant effect of RET. However, smaller reductions in depressive symptoms were derived from randomized clinical trials with blinded allocation and/or assessment. Conclusions and Relevance Resistance exercise training significantly reduced depressive symptoms among adults regardless of health status, total prescribed volume of RET, or significant improvements in strength. Better-quality randomized clinical trials blinding both allocation and assessment and comparing RET with other empirically supported treatments for depressive symptoms are needed."
More to follow ...