Short-term bone biochemical response to a single bout of high-impact exercise.

Bone response to a single bout of exercise can be observed with biochemical markers of bone formation and resorption. The purpose of this study was to examine the response of bone biochemical markers to a single bout of exhaustive high-impact exercise. 15 physically active young subjects volunteered to participate. The subjects performed continuous bilateral jumping with the ankle plantarflexors at 65 % of maximal ground reaction force (GRF) until exhaustion. Loading was characterized by analyzing the GRF recorded for the duration of the exercise. Venous blood samples were taken at baseline, immediately after, 2h and on day 1 and day 2 after the exercise. Procollagen type I amino terminal propeptide (P1NP, marker of bone formation) and carboxyterminal crosslinked telopeptide (CTx, marker of bone resorption) were analyzed from the blood samples. CTx increased significantly (32 %, p = 0.015) two days after the exercise and there was a tendensy towards increase seen in P1NP (p = 0.053) one day after the exercise. A significant positive correlation (r = 0.49 to 0.69, p ≤ 0.038) was observed between change in P1NP from baseline to day 1 and exercise variables (maximal slope of acceleration, body weight (BW) adjusted maximal GRF, BW adjusted GRF exercise intensity and osteogenic index). Based on the two biochemical bone turnover markers, it can be concluded that bone turnover is increased in response to a very strenuous single bout of exhaustive high-impact exercise. Key pointsStudies on bone acute biochemical response to loading have yielded unequivocal results.There is a paucity of research on the biochemical bone response to high impact exercise.An increase in bone turnover was observed one to two days post exercise.

The distribution of melanopsin (OPN4) protein in the human brain.

Until now, melanopsin (OPN4) - a specialized photopigment being responsive especially to blue light wavelengths - has not been found in the human brain at protein level outside the retina. More specifically, OPN4 has only been found in about 2% of retinal ganglion cells (i.e. in intrinsically photosensitive retinal ganglion cells), and in a subtype of retinal cone-cells. Given that Allen Institute for Brain Science has described a wide distribution of OPN4 mRNA in two human brains, we aimed to investigate whether OPN4 is present in the human brain also at protein level. Western blotting and immunohistochemistry, as well as immunoelectron microscopy, were used to analyse the existence and distribution of OPN4 protein in 18 investigated areas of the human brain in samples obtained in forensic autopsies from 10 male subjects (54 ± 3.5 years). OPN4 protein expression was found in all subjects, and, furthermore, in 5 out of 10 subjects in all investigated brain areas localized in membranous compartments and cytoplasmic vesicles of neurons. To our opinion, the wide distribution of OPN4 in central areas of the human brain evokes a question whether ambient light has important straight targets in the human brain outside the retinohypothalamic tract (RHT). Further studies are, however, needed to investigate the putative physiological phototransductive actions of inborn OPN4 protein outside the RHT in the human brain.

Exercise capacity and mortality - a follow-up study of 3033 subjects referred to clinical exercise testing.

BACKGROUND: Exercise stress testing is used as a diagnostic and prognostic tool. We determined the prognostic significance of exercise test findings for cardiovascular (CVD) and all-cause mortality in men and women. MATERIAL AND METHODS: 3033 subjects underwent a symptom-limited bicycle exercise test. Exercise capacity was defined as the mean of last four minutes of exercise workload. RESULTS: During an average follow-up of 19 years, 186 (11.6%) CVD and 370 (20.6%) all-cause deaths in men and 57 (5.0%) CVD and 155 (12.5%) all-cause deaths in women occurred. Among exercise test variables (workload, ECG, BP, HR), exercise capacity was the strongest predictor of mortality. Low exercise capacity (1st quartile) was associated with a hazard ratio of 4.2 (95% CI: 1.7, 10.8) for CVD and 4.0 (95% CI: 2.5, 6.4) for all-cause mortality compared with high exercise capacity (4th quartile) among men and in women with a 5.4-fold (95% CI: 1.2, 24.0) risk for CVD and 2.3-fold (95% CI: 1.2, 4.3) risk for all-cause mortality, respectively. The relationship between other exercise test variables and mortality was much weaker. CONCLUSIONS: Among exercise test variables exercise capacity was the strongest predictor of CVD and all-cause mortality in both genders, and especially CVD deaths in women. Key Messages Exercise capacity was the most powerful predictor of CVD and all-cause mortality in both men and women. Low exercise capacity is a strong predictor of CVD death, especially among women.

Determinants of lower-body muscle power in early postmenopausal women.

OBJECTIVES: To investigate the association between muscle size, density, and fiber composition; body composition; maximal isometric knee extension strength (KES); and lower-body muscle power in healthy postmenopausal women. DESIGN: Cross-sectional analysis of baseline data from a 1-year randomized controlled experiment. SETTING: University-based research laboratory. PARTICIPANTS: Seventy-eight healthy postmenopausal women aged 50 to 57. MEASUREMENTS: Maximal lower-body muscle power was assessed using vertical jump height (VJH). Maximal isometric KES was measured on a dynamometer chair. Computed tomography scans were used to determine lean-tissue cross-sectional area and density of the thigh and lower leg muscles. Relative area occupied by type I, IIa, IIax, and IIx muscle fibers was assessed from the vastus lateralis muscle. lean body mass and total body fat mass were assessed using bioelectrical impedance. RESULTS: High VJH was associated with low body fat mass, high KES, and high density of thigh and lower leg muscles. Multivariate linear regression modeling revealed that high thigh muscle density (beta=0.242; P=.019), relative area occupied by the fastest muscle fiber types (IIax+IIx; beta=0.246; P=.007), KES (beta=0.247; P=.007), and low body fat mass (beta=-0.455; P<.001) were independently associated with high VJH, accounting for 45% of the variability in VJH. CONCLUSION: This study showed that thigh muscle composition, muscle strength, and body fat mass are important determinants of lower-body muscle power production during weight-bearing activity in healthy postmenopausal women.

Collagen synthesis and degradation in polyneuropathy and myopathies.

To determine the mechanisms underlying the changes in collagen metabolism responsible for muscle fibrosis in patients with neuromuscular diseases, the synthesis and degradation of collagens was studied in muscles of patients with polyneuropathy and noninflammatory myopathies. The mRNA levels for type I, III, and IV collagens and immunohistochemical staining intensities for collagen propeptides and telopeptides were increased in polyneuropathy, suggesting enhanced synthesis of collagens. In myopathy, the mRNA levels were at the control level. Matrix metalloproteinase (MMP)-2 mRNA level was increased in polyneuropathy, although the quantity of proMMP-2 was not changed. An increase in type IV collagen concentration and proMMP-9 expression was observed in polyneuropathy but not in myopathies. Our results suggest that intramuscular accumulation of type IV collagen occurs in polyneuropathy, possibly leading to thickening of the capillary and muscle fiber basement membranes. This may complicate the transportation of nutrients and cellular excreta between blood and muscle cells.

Short-term effects of forced eccentric contractions on collagen synthesis and degradation in rat skeletal muscle.

Acute downhill running has been shown to activate matrix metalloproteinase- (MMP-) 2 and to change type IV collagen concentration in some muscle types. In order to study the influence of more intense exercise on total collagen and type IV collagen concentrations, molecules regulating their synthesis and degradation were investigated after forced lengthening contractions in rat skeletal muscle. Tibialis anterior (TA) muscle of 24 male Wistar rats was subjected to 240 forced lengthening contractions. TA muscle was excised at consecutive time points (0 and 6 h, 2, 4, and 7 days) after stimulation. With immunohistochemistry, types I, III and IV collagen were located in the swollen, necrotic and regenerated fibres in a similar manner as in intact undamaged skeletal muscle fibre. An increase in the activity of prolyl 4-hydroxylase was indicative of an overall elevated collagen biosynthesis. No change was demonstrated in total collagen concentration, whereas type IV collagen concentration increased after exercise. MMP-2 and MMP-9, which are the proteins that degrade type IV collagen, elevated after exercise. In conclusion, the increase in type IV collagen concentration seems to be the result of an increase in both the synthesis and activation of degrading enzymes and their inhibitors during recovery after forced lengthening contractions.