Are elderly construction workers sufficiently fit for heavy manual labour?

This study analysed the work ability of elderly construction workers. Forty male construction workers, 20 young (age < 33 yrs) and 20 senior (age>44 yrs) workers, were tested regarding aerobic power (VO2max) and muscle strength. The aerobic demand of a number of tasks in construction work was measured and compared with the workers' aerobic power. VO2max was higher for the young, and they performed better on most muscle strength tests. The measurements showed that about half of the senior workers had to use more than 30% of their maximum oxygen uptake on some tasks. In conclusion, because elderly construction workers decline in physical fitness, they are more exposed to overload when performing heavy manual work than are their younger peers. Increasing their individual fitness or adjusting their workload may be important for staying in the workforce for such workers. PRACTITIONER SUMMARY: Construction workers must occasionally perform strenuous work tasks that may endanger their safety. This was more often the case for elderly workers investigated here. Elderly workers should therefore be particularly observant of their physical fitness, and should possibly train during leisure time to improve their fitness.

Working suspended in a harness rig: A comparative study of musculoskeletal health complaints in rope access technicians and controls.

BACKGROUND: Rope access technique is an alternative method for gaining access to challenging work locations. There is limited knowledge about possible adverse effects of this technique on the workers' health. OBJECTIVE: To compare the frequency of bodily regions with pain in rope access technicians with craft workers and the working population in general. METHODS: The one-month prevalence of pain in the head, neck, distal upper extremities, lower back and lower extremities was recorded in rope access technicians (n = 95), "craft workers" (n = 289) and "all occupations" (n = 1563). RESULTS: An increased prevalence of pain in the neck, distal upper extremities and lower extremities was found for the rope access technicians compared with all occupations (p-values <0.01). Compared with the craft workers, relatively more rope access technicians reported pain in the lower extremity region (p <0.01) while the groups were similar for the other body regions. CONCLUSIONS: The prevalence of pain in the lower extremities was higher in rope access technicians compared with craft workers, while no differences were found for other body regions. The increased prevalence of pain in the neck and distal upper extremities in the technicians compared with all occupations may therefore be related to the work tasks and not the access technique.

Adrenaline potentiates insulin-stimulated PKB activation via cAMP and Epac: implications for cross talk between insulin and adrenaline.

Adrenaline and insulin are two of the most important hormones regulating a number of physiological processes in skeletal muscle. Insulin's effects are generally requiring PKB and adrenaline effects cAMP and PKA. Recent evidence indicates cAMP can regulate PKB in some cell types via Epac (Exchange protein directly activated by cAMP). This suggests possible crossover between insulin and adrenaline signalling in muscle. Here we find that adrenaline alone did not influence PKB activation, but adrenaline dramatically potentiated insulin-stimulated phosphorylation of PKB (both Ser473 and Thr308) and of PKBalpha and PKBbeta enzyme activities. These effects were inhibited by wortmannin but adrenaline did not increase insulin-stimulated p85alpha PI 3-kinase activity. Adrenaline effects occurred via beta-adrenergic receptors and accumulation of cAMP. Interestingly, the Epac specific cAMP analogue 8-(4-chlorophenylthio)-2'-O-methyl-cAMP potentiated insulin-stimulated PKB phosphorylation in a similar manner as adrenaline did without activating glycogen phosphorylase. Inhibition of PKA by H89 decreased adrenaline-stimulated glycogen phosphorylase activation but increased PKB activation, which further supports that adrenaline increases insulin-stimulated PKB phosphorylation via Epac. Further, while adrenaline and the Epac activator alone did not promote p70(S6K) Thr389 phosphorylation, they potentiated insulin effects. In conclusion, adrenaline potentiates insulin-stimulated activation of PKB and p70(S6K) via cAMP and Epac in skeletal muscle. Furthermore, the fact that adrenaline alone did not activate PKB or p70(S6K) suggests that a hormone can be a potent regulator of signalling despite no effects being seen when co-activators are lacking.

Association between perceived present working conditions and demands versus attitude to early retirement among construction workers.

BACKGROUND: Early retirement is an increasing problem in the construction industry. There is limited information about causes leading employees to leave working life early. We have compared construction workers present situation with their perception of future demands at work to avoid early retirement. METHODS: All 87 employees in a medium-sized Norwegian construction company participated in the study. All were men and answered questionnaires on health and pain, work ability, mechanical exposure, psychosocial conditions, and demands regarding future working conditions. RESULTS: Most workers showed good work ability, irrespective of age. Many reported high levels of mechanical exposure at work. The level of musculoskeletal pain was higher in the middle-aged (30-50 year old) age groups and seniors aged over 50 years than among the youngest workers less than 30 years of age. All workers reported that good health was important for continued working. Most workers stated that future work must not be too physically demanding. Many workers reported relatively low job satisfaction; consequently an interesting job was rated as important for continuing work. Good social conditions were a high priority. CONCLUSIONS: According to the examined construction workers, good health and reduced levels of mechanical exposure at work are essential to avoid early retirement.

Adrenaline potentiates insulin-stimulated PKB activation in the rat fast-twitch epitrochlearis muscle without affecting IRS-1-associated PI 3-kinase activity.

We have previously shown in the rat slow-twitch soleus muscle that adrenaline greatly potentiates insulin-stimulated protein kinase B (PKB) phosphorylation without having an effect alone. However, insulin signalling capacity through the PKB pathway is higher in soleus than in fast-twitch muscles, whereas adrenaline activates phosphorylase more strongly in epitrochlearis. Therefore, the aim of the present study was to investigate the interaction between adrenaline and insulin signalling in the fast-twitch epitrochlearis muscle. Insulin increased insulin receptor substrate-1 (IRS-1)-associated phosphoinositide (PI) 3-kinase activity threefold, and adrenaline did not influence basal or insulin-stimulated PI 3-kinase activity. Insulin but not adrenaline increased PKB activity and phosphorylation of Ser(473) and Thr(308). It is interesting to note that adrenaline potentiated insulin-stimulated PKB activity and PKB Ser(473) and Thr(308) phosphorylation. These effects were mimicked by dibutyryl-cyclic adenosine monophosphate (db-cAMP). Adrenaline and db-cAMP increased glycogen synthase kinase (GSK)-3beta Ser(9) phosphorylation independently of PKB activation and enhanced insulin-stimulated GSK-3beta Ser(9) phosphorylation. Although adrenaline increased GSK-3 phosphorylation (inhibiting activity), phosphorylation of its target sites on glycogen synthase was increased, and adrenaline blocked insulin-stimulated glycogen synthase dephosphorylation of Ser(641) and Ser(645,649,653,657), glycogen synthase activation and glycogen synthesis. Insulin-stimulated glucose transport was not influenced by adrenaline despite the increased PKB activation. In conclusion, as in the slow-twitch soleus muscle, adrenaline potentiates insulin-stimulated PKB activation in the fast-twitch glycolytic epitrochlearis muscle without increasing IRS-1-associated PI 3-kinase activity. Furthermore, adrenaline induces phosphorylation of a pool of GSK-3 that is not involved in the regulation of glycogen metabolism. These results indicate that the combination of adrenaline and insulin may activate novel signalling molecules rather than just summing up their effects on linear pathways.

Muscle glycogen inharmoniously regulates glycogen synthase activity, glucose uptake, and proximal insulin signaling.

Insulin-stimulated glucose uptake and incorporation of glucose into skeletal muscle glycogen contribute to physiological regulation of blood glucose concentration. In the present study, glucose handling and insulin signaling in isolated rat muscles with low glycogen (LG, 24-h fasting) and high glycogen (HG, refed for 24 h) content were compared with muscles with normal glycogen (NG, rats kept on their normal diet). In LG, basal and insulin-stimulated glycogen synthesis and glycogen synthase activation were higher and glycogen synthase phosphorylation (Ser(645), Ser(649), Ser(653), Ser(657)) lower than in NG. GLUT4 expression, insulin-stimulated glucose uptake, and PKB phosphorylation were higher in LG than in NG, whereas insulin receptor tyrosyl phosphorylation, insulin receptor substrate-1-associated phosphatidylinositol 3-kinase activity, and GSK-3 phosphorylation were unchanged. Muscles with HG showed lower insulin-stimulated glycogen synthesis and glycogen synthase activation than NG despite similar dephosphorylation. Insulin signaling, glucose uptake, and GLUT4 expression were similar in HG and NG. This discordant regulation of glucose uptake and glycogen synthesis in HG resulted in higher insulin-stimulated glucose 6-phosphate concentration, higher glycolytic flux, and intracellular accumulation of nonphosphorylated 2-deoxyglucose. In conclusion, elevated glycogen synthase activation, glucose uptake, and GLUT4 expression enhance glycogen resynthesis in muscles with low glycogen. High glycogen concentration per se does not impair proximal insulin signaling or glucose uptake. "Insulin resistance" is observed at the level of glycogen synthase, and the reduced glycogen synthesis leads to increased levels of glucose 6-phosphate, glycolytic flux, and accumulation of nonphosphorylated 2-deoxyglucose.

Quantitative determination of cell surface beta-adrenoceptors in different rat skeletal muscles.

In the present study, the density of cell surface beta-adrenergic receptors was determined in different skeletal muscles using the hydrophilic ligand [3H]CGP 12177. The density of beta-adrenergic receptors was highest in the slow-twitch soleus muscle (32.8+/-0.9 fmol mg dw(-1)) and lowest in the fast-twitch glycolytic white gastrocnemius (10.4+/-0.5 fmol mg dw(-1)) beta-Adrenoceptor density correlated closely with the percentage of type-I fibres (r=0.979; P<0.0001) and inversely with the percentage of type-IIB fibres (r=696; P<0.03). Incubation with isoprenaline (10 microM) for 30 min decreased the density of beta-adrenergic receptors in the cell surface from 32.9+/-0.8 to 19.3+/-0.7 fmol mg dw(-1) in the soleus and from 16.8+/-1.0 to 12.0+/-0.7 fmol mg dw(-1) in the epitrochlearis. Internalisation appeared rapid (half-time less than 5 min). To study externalisation of beta-adrenergic receptors, soleus strips were incubated 30 min with 10 microM isoprenaline and then transferred to buffer without agonist. The first incubation reduced the density to approximately 50%, the subsequent incubation without agonist increased cell surface receptor density to approximately 80% of the initial density after 1 h. No further increase was observed over the next 2 h, suggesting that some of the receptors had been degraded. Insulin or contractile activity did not influence rate of externalisation.