Exercise-induced sweat nitrogen excretion: evaluation of a regional collection method using gauze pads

Summary: The exercise-induced sweat nitrogen excretion was investigated during a 45-minute run at moderate intensity on a treadmill. Sweat was collected with a regional collection technique using gauze pads and compared with the whole-body wash-down (WBW) method. In the regional collection, sweat was sampled from the upper back (UB), lower back (LB), abdomen (AB), and thigh (TH). Additionally, the relation of sweat urea, ammonia, and amino acids was investigated with the regional collection method during a second 45-minute run. Independent of the sweat collection method, a significant and positive correlation was found between sweat rate and the excretion rate of the largest nitrogen fraction urea, suggesting that the sweating response to exercise might be one of the most important factors determining absolute sweat nitrogen losses. The urea nitrogen excretion was nearly 140 mg·h−1 in the second run, representing the largest nitrogen fraction. Ammonia nitrogen and amino acid-derived nitrogen rate were approximately 30 mg·h−1 and 10 mg·h−1, respectively. The comparison of the sampling methods during the first run revealed that the urea nitrogen rate was significantly higher, but the ammonia nitrogen rate significantly lower in the WBW. After summing urea and ammonia nitrogen, no significant difference between the methods was observed anymore, except for UB. It is concluded that the regional collection method using gauze pads is a valuable approach to measure exercise-induced sweat nitrogen losses during moderate running exercis

Role of peripheral quantitative computed tomography in identifying disuse osteoporosis in paraplegia

Objective: Disuse osteoporosis is a major long-term health consequence of spinal cord injury (SCI) that still needs to be addressed. Its management in SCI should begin with accurate diagnosis, followed by targeted treatments in the most vulnerable subgroups. We present data quantifying disuse osteoporosis in a cross-section of the Scottish paraplegic population to identify subgroups with lowest bone mineral density (BMD). Materials and Methods: Forty-seven people with chronic SCI at levels T2-L2 were scanned using peripheral Quantitative Computed Tomography (pQCT) at four tibial sites and two femoral sites, at the Queen Elizabeth National Spinal Injuries Unit, Glasgow (U.K.). At the distal epiphyses, trabecular BMD (BMDtrab), total BMD, total bone cross-sectional area (CSA), and bone mineral content (BMC) were determined. In the diaphyses, cortical BMD, total bone CSA, cortical CSA, and BMC were calculated. Bone, muscle and fat CSAs were estimated in the lower leg and thigh. Results: BMDtrab decreased exponentially with time since injury, at different rates in the tibia and femur. At most sites, female paraplegics had significantly lower BMC, total bone CSA and muscle CSA than male paraplegics. Subjects with lumbar SCI tended to have lower bone values and smaller muscle CSAs than in thoracic SCI. Conclusion: At the distal epiphyses of the tibia and femur, there is generally a rapid and extensive reduction in BMDtrab after SCI. Female subjects, and those with lumbar SCI, tend to have lower bone values than males or those with thoracic SCI, respectively. Keywords: Bone loss, osteoporosis, paraplegia, peripheral Quantitative Computed Tomography, spinal cord injur

Decrease of physical activity level in adolescents with limb fractures: an accelerometry-based activity monitor study

<p>Abstract</p> <p>Background</p> <p>Immobilization and associated periods of inactivity can cause osteopenia, the physiological response of the bone to disuse. Mechanical loading plays an essential role in maintaining bone integrity. Skeletal fractures represent one cause of reduction of the physical activity (PA) level in adolescents. The purpose of this study was to quantify the reduction of PA in adolescents with limb fractures during the cast immobilization period compared with healthy controls.</p> <p>Methods</p> <p>Two hundred twenty adolescents were divided into three groups: those with upper limb fractures (50 cases); lower limb fractures (50 cases); and healthy cases (120 cases). Patients and their healthy peers were matched for gender, age, and seasonal assessment of PA. PA level was assessed during cast immobilization by accelerometer. Time spent in PA in each of the different intensity levels - sedentary, light, moderate, and vigorous - was determined for each participant and expressed in minutes and as a percentage of total valid time.</p> <p>Results</p> <p>Reduction in PA during cast immobilization was statistically significant in patients with limb fractures compared to healthy controls. The total PA count (total number of counts/min) was significantly lower in those with upper and lower limb fractures (-30.1% and -62.4%, respectively) compared with healthy controls (p < 0.0001 and p = 0.0003, respectively). Time spent in moderate-to-vigorous PA by patients with upper and lower limb injuries decreased by 36.9% (<it>p </it>= 0.0003) and 76.6% (<it>p </it>< 0.0001), respectively, and vigorous PA was reduced by 41.4% (<it>p </it>= 0.0008) and 84.4% (<it>p </it>< 0.0001), respectively.</p> <p>Conclusions</p> <p>PA measured by accelerometer is a useful and valid tool to assess the decrease of PA level in adolescents with limb fractures. As cast immobilization and reduced PA are known to induce bone mineral loss, this study provides important information to quantify the decrease of skeletal loading in this patient population. The observed reduction of high intensity skeletal loading due to the decrease in vigorous PA may explain osteopenia due to disuse, and these data should be kept in mind by trauma practitioners to avoid any unnecessary prolongation of the cast immobilization period.</p

Increased serum levels of non-collagenous matrix proteins (cartilage oligomeric matrix protein and melanoma inhibitory activity) in marathon runners

AbstractObjective Marathon runners have an increased risk of developing joint disease. During and after a 42-km run, elevation of multiple cytokines occurs in the blood, reflecting inflammatory processes. We compared this cytokine response with serum levels of cartilage oligomeric matrix protein (COMP) and melanoma inhibitory activity (MIA), two markers for joint metabolism and/or damage.Methods Serum from eight endurance-trained runners was collected shortly before the start of a marathon run, after 31km, 42km, 2h after the end, on the first and on the second morning after the run. For comparison, serum was obtained from 35 healthy controls and 80 patients with knee joint injury, rheumatoid arthritis or osteoarthritis. Serum levels of C-reactive protein (CRP), interleukin-1β (IL-1β), interleukin-1 receptor antagonist (IL-1RA), interleukin-6 (IL-6), tumor necrosis factor-α (TNF-α), soluble interleukin-6 receptor (sIL-6R, gp80), soluble tumor necrosis factor receptor II (sTNFRII, p75), COMP and MIA were measured by ELISA.Results Compared with healthy controls, the runner's baseline serum levels of TNF-α, sIL-6R, COMP and MIA were significantly increased. COMP and MIA levels, higher than the upper normal limits of 5μg/ml and 6ng/ml respectively, were found in seven and five of eight runners. The elevated levels of COMP were similar to those found in joint injury or osteoarthritis, and the elevated levels of MIA were comparable to those reported in rheumatoid arthritis. During the run, the serum levels of IL-1RA, IL-6, TNF-α and COMP rose significantly, and gradually returned to baseline within 24h. Only modest changes of CRP, sIL-6R, sTNFRII and MIA occurred during the run. Late elevations of CRP and MIA were observed after 24 and 48h. The correlation analysis suggests associations between COMP, sIL-6R, TNF-α, IL-1RA on one hand and sTNFRII, and MIA and CRP on the other hand.Conclusions Elevated baseline levels of COMP and MIA might reflect increased joint matrix turnover and/or damage due to prior extreme physical training. During the run, COMP was increasing possibly due to the severe physical strain on joint structures, associated with the early inflammation. After the run, MIA and CRP increased within 24h, suggesting a correlation with later inflammatory processes. Thus, our data suggest that COMP and MIA are markers for distinct aspects of joint metabolism and/or damage in both disease and sport

Changes of basic bone turnover parameters in short-term and long-term patients with spinal cord injury

The bone mineral density (BMD), the cross- links (PYD, DPD and NTx) and the bone specific alcaline phosphatase (BAP) was investigated in a cross-sectional study in 62 male patients with spinal cord injury (SCI), n = 28 short-term (0–1 year after SCI) and n = 34 long-term SCI patients (> 5 years after SCI). Knowledge about this parameters are necessary to find an adequate therapy for this special kind of osteoporosis. Immobilisation osteoporosis in SCI patients is a well-known problem that may lead to pathological fractures. Little is known regarding the extend of the osteoporosis as well as the causative factors. Measurements of the BMD in the proximal femur and the lumbar spine were performed with dual-energy-X-ray-absorptiometry (DEXA), of the osteoblast marker BAP (bone specific alkaline phosphatase) from serum and the osteoclast markers PYD (pyridinoline), DPD (desoxy-pyridinoline) and NTx (N-telopeptide of collagen type I) from urine. We found a significant decrease of BMD in the proximal femur and no relevant change in the lumbar spine compared to an age- and sex correlated control group (Z-score) in short-term and long-term SCI patients. There was a significant bone loss at the proximal femur between short and long-term SCI patients, whereas at the lumbar spine the BMD even slightly increases. Bone resorption (cross-links) was increased in both groups, though in long-term SCI patients it is significantly decreased compared to short-term SCI patients (DPD from 211.7 u/g creatinine to 118.1 u/g creatinine; NTx from 215.1 nmol/mmol creatinine to 83,6 nmol/mmol creatinine). The bone formation marker BAP is slightly below normal range in both groups (12.3 U/l in short-term, 9.7 U/l in long- term SCI patients). Only the proximal femur is affected by the immobilisation osteoporosis of SCI patients, therefore the BMD measurements in these patients should be performed at the lower limb. The problem of the immobilisation osteoporosis in SCI patients is the striking increase of bone resorption and the missing reaction of the bone formation