Aerobic capacity reference data in 3816 healthy men and women 20-90 years

Purpose: To provide a large reference material on aerobic fitness and exercise physiology data in a healthy population of Norwegian men and women aged 20–90 years. Methods: Maximal and sub maximal levels of VO2, heart rate, oxygen pulse, and rating of perceived exertion (Borg scale: 6–20) were measured in 1929 men and 1881 women during treadmill running. Results: The highest VO2max and maximal heart rate among men and women were observed in the youngest age group (20–29 years) and was 54.4±8.4 mL·kg−1·min−1 and 43.0±7.7 mL·kg−1·min−1 (sex differences, p<0.001) and 196±10 beats·min−1 and 194±9 beats·min−1 (sex differences, p<0.05), respectively, with a subsequent reduction of approximately 3.5 mL·kg−1·min−1 and 6 beats·min−1 per decade. The highest oxygen pulses were observed in the 3 youngest age groups (20–29 years, 30–39 years, 40–49 years) among men and women; 22.3 mL·beat−1±3.6 and 14.7 mL·beat−1±2.7 (sex differences, p<0.001), respectively, with no significant difference between these age groups. After the age of 50 we observed an 8% reduction per decade among both sexes. Borg scores appear to give a good estimate of the relative exercise intensity, although observing a slightly different relationship than reported in previous reference material from small populations. Conclusion: This is the largest European reference material of objectively measured parameters of aerobic fitness and exercise-physiology in healthy men and women aged 20–90 years, forming the basis for an easily accessible, valid and understandable tool for improved training prescription in healthy men and women.© 2013 Loe et al. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited

Foreword

Background: This study compares the levels of algesic substances between subjects with trapezius myalgia (TM) and healthy controls (CON) and explores the multivariate correlation pattern between these substances, pain, and metabolic status together with relative blood flow changes reported in our previous paper (Eur J Appl Physiol 108: 657-669, 2010). Methods: 43 female workers with (TM) and 19 females without (CON) trapezius myalgia were - using microdialysis - compared for differences in interstitial concentrations of interleukin-6 (IL-6), bradykinin (BKN), serotonin (5-HT), lactate dehydrogenas (LDH), substance P, and N-terminal propeptide of procollagen type I (PINP) in the trapezius muscle at rest and during repetitive/stressful work. These data were also used in multivariate analyses together with previously presented data (Eur J Appl Physiol 108: 657-669, 2010): trapezius muscle blood flow, metabolite accumulation, oxygenation, and pain development and sensitivity. Results: Substance P was significantly elevated in TM (p=0.0068). No significant differences were found in the classical algesic substances (p: 0.432-0.926). The multivariate analysis showed that blood flow related variables, interstitial concentrations of metabolic (pyruvate), and algesic (BKN and K+) substances were important for the discrimination of the subjects to one of the two groups (R-2: 0.19-0.31, pless than0.05). Pain intensity was positively associated with levels of 5-HT and K+ and negatively associated with oxygenation indicators and IL-6 in TM (R-2: 0.24, pless than0.05). A negative correlation existed in TM between mechanical pain sensitivity of trapezius and BKN and IL-6 (R-2: 0.26-0.39, pless than0.05). Conclusion: The present study increased understanding alterations in the myalgic muscle. When considering the system-wide aspects, increased concentrations of lactate, pyruvate and K+ and decreased oxygenation characterized TM compared to CON. There are three major possible explanations for this finding: the workers with pain had relatively low severity of myalgia, metabolic alterations preceded detectable alterations in levels of algesics, or peripheral sensitization and other muscle alterations existed in TM. Only SP of the investigated algesic substances was elevated in TM. Several of the algesics were of importance for the levels of pain intensity and mechanical pain sensitivity in TM. These results indicate peripheral contribution to maintenance of central nociceptive and pain mechanisms and may be important to consider when designing treatments.Funding Agencies|Danish Medical Research Council [22-03-0264]; Danish Rheumatism Association [233-1149-02.02.04]; Swedish Research Council [K2011-69X-21874-01-6]; Swedish Council for Working Life and Social Research [2010-0913]</p

The effect of nitric oxide synthase inhibition with and without inhibition of prostaglandins on blood flow in different human skeletal muscles

Purpose Animal studies suggest that the inhibition of nitric oxide synthase (NOS) affects blood flow differently in different skeletal muscles according to their muscle fibre type composition (oxidative vs glycolytic). Quadriceps femoris (QF) muscle consists of four different muscle parts: vastus intermedius (VI), rectus femoris (RF), vastus medialis (VM), and vastus lateralis (VL) of which VI is located deep within the muscle group and is generally regarded to consist mostly of oxidative muscle fibres.Methods We studied the effect of NOS inhibition on blood flow in these four different muscles by positron emission tomography in eight young healthy men at rest and during one-leg dynamic exercise, with and without combined blockade with prostaglandins.Results At rest blood flow in the VI (2.6 +/- 1.1 ml/100 g/min) was significantly higher than in VL (1.9 +/- 0.6 ml/100 g/min, p = 0.015) and RF (1.7 +/- 0.6 ml/100 g/min, p = 0.0015), but comparable to VM (2.4 +/- 1.1 ml/100 g/min). NOS inhibition alone or with prostaglandins reduced blood flow by almost 50% (p < 0.001), but decrements were similar in all four muscles (drug x muscle interaction, p = 0.43). During exercise blood flow was also the highest in VI (45.4 +/- 5.5 ml/100 g/min) and higher compared to VL (35.0 +/- 5.5 ml/100 g/min), RF (38.4 +/- 7.4 ml/100 g/min), and VM (36.2 +/- 6.8 ml/100 g/min). NOS inhibition alone did not reduce exercise hyperemia (p = 0.51), but combined NOS and prostaglandin inhibition reduced blood flow during exercise (p = 0.002), similarly in all muscles (drug x muscle interaction, p = 0.99).Conclusion NOS inhibition, with or without prostaglandins inhibition, affects blood flow similarly in different human QF muscles both at rest and during low-to-moderate intensity exercise

Effect of nitric oxide synthase inhibition on the exchange of glucose and fatty acids in human skeletal muscle

BACKGROUND: The role of nitric oxide in controlling substrate metabolism in humans is incompletely understood. METHODS: The present study examined the effect of nitric oxide blockade on glucose uptake, and free fatty acid and lactate exchange in skeletal muscle of eight healthy young males. Exchange was determined by measurements of muscle perfusion by positron emission tomography and analysis of arterial and femoral venous plasma concentrations of glucose, fatty acids and lactate. The measurements were performed at rest and during exercise without (control) and with blockade of nitric oxide synthase (NOS) with N(G)-monomethyl-l-arginine (L-NMMA). RESULTS: Glucose uptake at rest was 0.40 ± 0.21 μmol/100 g/min and increased to 3.71 ± 2.53 μmol/100 g/min by acute one leg low intensity exercise (p < 0.01). Prior inhibition of NOS by L-NMMA did not affect glucose uptake, at rest or during exercise (0.40 ± 0.26 and 4.74 ± 2.69 μmol/100 g/min, respectively). In the control trial, there was a small release of free fatty acids from the limb at rest (−0.05 ± 0.09 μmol/100 g/min), whereas during inhibition of NOS, there was a small uptake of fatty acids (0.04 ± 0.05 μmol/100 g/min, p < 0.05). During exercise fatty acid uptake was increased to (0.89 ± 1.07 μmol/100 g/min), and there was a non-significant trend (p = 0.10) for an increased FFA uptake with NOS inhibition 1.23 ± 1.48 μmol/100 g/min) compared to the control condition. Arterial concentrations of all substrates and exchange of lactate over the limb at rest and during exercise remained unaltered during the two conditions. CONCLUSION: In conclusion, inhibition of nitric oxide synthesis does not alter muscle glucose uptake during low intensity exercise, but affects free fatty acid exchange especially at rest, and may thus be involved in the modulation of energy metabolism in the human skeletal muscle

Skeletal Muscle Myofibrillar and Sarcoplasmic Protein Synthesis Rates Are Affected Differently by Altitude-Induced Hypoxia in Native Lowlanders

As a consequence to hypobaric hypoxic exposure skeletal muscle atrophy is often reported. The underlying mechanism has been suggested to involve a decrease in protein synthesis in order to conserve O2. With the aim to challenge this hypothesis, we applied a primed, constant infusion of 1-13C-leucine in nine healthy male subjects at sea level and subsequently at high-altitude (4559 m) after 7–9 days of acclimatization. Physical activity levels and food and energy intake were controlled prior to the two experimental conditions with the aim to standardize these confounding factors. Blood samples and expired breath samples were collected hourly during the 4 hour trial and vastus lateralis muscle biopsies obtained at 1 and 4 hours after tracer priming in the overnight fasted state. Myofibrillar protein synthesis rate was doubled; 0.041±0.018 at sea-level to 0.080±0.018%⋅hr−1 (p<0.05) when acclimatized to high altitude. The sarcoplasmic protein synthesis rate was in contrast unaffected by altitude exposure; 0.052±0.019 at sea-level to 0.059±0.010%⋅hr−1 (p>0.05). Trends to increments in whole body protein kinetics were seen: Degradation rate elevated from 2.51±0.21 at sea level to 2.73±0.13 µmol⋅kg−1⋅min−1 (p = 0.05) at high altitude and synthesis rate similar; 2.24±0.20 at sea level and 2.43±0.13 µmol⋅kg−1⋅min−1 (p>0.05) at altitude. We conclude that whole body amino acid flux is increased due to an elevated protein turnover rate. Resting skeletal muscle myocontractile protein synthesis rate was concomitantly elevated by high-altitude induced hypoxia, whereas the sarcoplasmic protein synthesis rate was unaffected by hypoxia. These changed responses may lead to divergent adaptation over the course of prolonged exposure