Sex and muscle structural lipids in obese subjects – an impact on insulin action?

Background Long‐chain polyunsaturated fatty acid (LCPUFA) especially the n‐3‐FA of skeletal muscle phospholipids may facilitate insulin action, whereas saturated and trans‐FA act oppositely. Community studies show that non‐diabetic weight matched obese men and women display similar insulin resistance, despite the fact that an android fat distribution is detrimental to insulin action. The increased extramyocellular fat mass of obese women may act in a paracrine manner such that its release of free FA and cytokines may hamper in situ desaturation and elongation of FA in skeletal muscle phospholipids. Material and methods To test the hypothesis that obese women may display an inferior FA composition compared to obese men, the FA composition of skeletal muscle phospholipids was determined in vastus lateralis biopsies obtained from 12 non‐diabetic obese women with a typical gynoid fat distribution, nine non‐diabetic obese men with a typical android fat distribution and 12 (seven females) lean age matched healthy controls (body mass index 34·6 ± 1·0 kg m^?2, 36·5 ± 1·2 and 22·5 ± 0·5; age 47 ± 2 years, 51 ± 3 and 49 ± 2). Results Obese women displayed decreased LCPUFA n‐3 and ratio of n‐3/n‐6 PUFA, whereas trans‐FA and palmitic‐FA (C16 : 0) were increased compared to obese men and controls (all Ps < 0·05). Plasma high‐density lipoprotein cholesterol (HDL‐C), triglycerides and a marker of insulin sensitivity were similar between obese women and men but impaired compared to controls (Ps < 0·05). Conclusions The data support the hypothesis that insulin resistant non‐diabetic obese men display a more optimal skeletal muscle phospholipid FA composition than their female counterparts, which may be a mechanism to compensate the detrimental effect on insulin action of an android fat distribution.     

Visfatin expression in subcutaneous adipose tissue of pre-menopausal women: relation to hormones and weight reduction

Background A novel adipokine, visfatin, was found to be related to adiposity in humans and regulated by a number of hormonal signals. The aim of this study was to investigate the relationships of visfatin expression in adipose tissue with potential regulatory factors such as insulin, testosterone and tumor necrosis factor‐α (TNF‐α) and to elucidate the effect of a diet induced weight reduction on adipose tissue mRNA expression and plasma levels of visfatin. Materials and methods Biopsies of subcutaneous abdominal adipose tissue (SCAAT) and plasma samples were obtained at the beginning of the study from 47 pre‐menopausal women (age 38·7 ± 1·7 years, body mass index (BMI) 27·9 ± 1·4 kg m^?2), consisting of 15 lean, 16 overweight and 16 obese subjects. The subgroup of 32 overweight/obese women (age 42·1 ± 1·9 years, BMI 31·2 ± 0·9 kg m^?2) underwent a 12 week hypocaloric weight reducing diet and samples were obtained at the end of the diet. Biopsy samples were analysed for visfatin and TNF‐α mRNA levels and plasma was analysed for relevant metabolites and hormones. Results In the group of 47 subjects visfatin mRNA expression in SCAAT was negatively correlated with plasma free testosterone (r = –0. 363, P < 0·05) and BMI (r = –0·558, P < 0·01) and positively associated with adipose tissue TNF‐α mRNA expression (r = 0·688, P < 0·01). The diet resulted in the reduction of body weight and in the decrease of plasma insulin, free testosterone and TNF‐α levels. In the group of overweight/obese subjects visfatin mRNA in SCAAT increased after the diet and the diet induced increase was positively correlated with the magnitude of body weight loss. Conclusion Visfatin mRNA expression in SCAAT is associated with TNF‐α expression, plasma free testosterone and BMI in pre‐menopausal women. A weight reducing hypocaloric diet results in the increase of visfatin mRNA in SCAAT.     

Acute resistance exercise using free weights on aortic wave reflection characteristics

Aortic wave reflection characteristics such as the augmentation index (AIx), wasted left ventricular pressure energy (ΔE_w) and aortic haemodynamics, such as aortic systolic blood pressure (ASBP), strongly predict cardiovascular events. The effects of acute resistance exercise (ARE) using free‐weight exercises on these characteristics are unknown. Therefore, we sought to determine the effects of acute free‐weight resistance exercise on aortic wave reflection characteristics and aortic haemodynamics in resistance‐trained individuals. Fifteen young, healthy resistance‐trained (9 ± 3 years) individuals performed two randomized sessions consisting of an acute bout of free‐weight resistance exercise (ARE) or a quiet control (CON). The ARE consisted of three sets of 10 repetitions at 75% one repetition maximum for squat, bench press and deadlift. In CON, the participants rested in the supine position for 30 min. Measurements were made at baseline before sessions and 10 min after sessions. A two‐way ANOVA was used to compare the effects of condition across time. There were no significant interactions for aortic or brachial blood pressures. Compared to rest, there were significant increases in augmentation pressure (rest: 5·7 ± 3·0 mmHg; recovery: 10·4 ± 5·7 mmHg, P = 0·002), AIx (rest: 116·8 ± 4·2%; recovery: 123·2 ± 8·4%, P = 0·002), AIx normalized at 75 bpm (rest: 5·2 ± 7·6%; recovery: 27·3 ± 13·2%, P<0·0001), ΔE_w (rest: 1215 ± 674 dynes s cm^?2; recovery: 2096 ± 1182 dynes s cm^?2, P = 0·008), and there was a significant decrease in transit time of the reflected wave (rest: 150·7 ± 5·8 ms; recovery 145·5 ± 5·6 ms, P<0·001) during recovery from ARE compared to CON. These data suggest that ARE using free‐weight exercises may have no effect on aortic and brachial blood pressure but may significantly alter aortic wave reflection characteristics.     

Endothelial nitric oxide synthase Glu298Asp gene polymorphism influences body composition and biochemical parameters but not the nitric oxide response to eccentric resistance exercise in elderly obese women

Both endothelial nitric oxide synthase (eNOS) gene polymorphism and nitric oxide (NO) are involved in important cardiovascular, muscular and inflammatory physiological mechanisms during ageing and response to exercise. The aim of this study was to investigate the NO kinetic response following an acute eccentric resistance exercise (ERE) session and the possible effect of the Glu298Asp eNOS gene polymorphism in elderly obese women. Eighty‐seven women (age 69·4 ± 6·1 years, body weight 74·9 ± 12·7 kg, height 151·9 ± 6·0 cm and BMI 32·5 ± 5·7 kg m^?2) completed seven sets of ten eccentric repetitions at 110% of the ten repetitions maximum (10RM). NO concentrations remained elevated up to 48 h following the acute ERE session as compared with baseline, for GG and GT/TT groups (P<0·05), with no differences between genotypes. The GG genotype group had higher body weight, prevalence of obesity (BMI classification – 81% versus 56%), BMI and higher relative muscle strength, while they had significantly lower triglycerides, VLDL and urea concentrations as compared with TT/TG group. In conclusion, NO remains elevated for up to 48 h after an acute ERE session, without genotype interaction. The TT/TG genotype had a negative impact on triglycerides, VLDL and urea concentrations. Thus, T carriers should increase their attention to cardiovascular risk factor and metabolic disorders.     

Obese children show increased intimal wall thickness and decreased pulse wave velocity

Objective: Childhood obesity confers an increased risk of vascular changes and adult cardiovascular disease. Using a high‐resolution ultrasound technique that enables separation of intimal and medial layers, we examined the intimal thickness (IT) and intimal–medial thickness (IMT) of radial (RA) and dorsal pedal (DPA) arteries and the pulse wave velocity (PWV) in overweight/obese children and adolescents and in healthy subjects. Methods and results: IT and IMT of RA and DPA and PWV were measured in 33 obese children and adolescents (13·9 ± 1·6 years) and in 18 matched lean controls (14·3 ± 2·2). Increased RA IT was found in the obese group, whereas no differences in RA IMT or medial thickness were observed. Obese females accounted for the entire difference in RA IT (P = 0·04). DPA IT was inversely correlated with HDL cholesterol in the obese group (?0·56, P = 0·0089). PWV was lower in the obese group than in the lean group (6·2 ± 0·8 versus 7·0 ± 0·9 m s^?1, respectively; P = 0·001). Conclusions: Obese children and adolescents, primarily females, present with increased RA IT. The decreased PWV in the obese versus lean subjects might reflect general vasodilatation.     

The impact of short duration,high intensity exercise on cardiac troponin release

The aim of this study was to assess the appearance of cardiac troponins (cTnI and/or cTnT) after a short bout (30 s) of ‘all‐out’ intense exercise and to determine the stability of any exercise‐related cTnI release in response to repeated bouts of high intensity exercise separated by 7 days recovery. Eighteen apparently healthy, physically active, male university students completed two all‐out 30 s cycle sprint, separated by 7 days. cTnI, blood lactate and catecholamine concentrations were measured before, immediately after and 24 h after each bout. Cycle performance, heart rate and blood pressure responses to exercise were also recorded. Cycle performance was modestly elevated in the second trial [6·5% increase in peak power output (PPO)]; there was no difference in the cardiovascular, lactate or catecholamine response to the two cycle trials. cTnI was not significantly elevated from baseline through recovery (Trial 1: 0·06 ± 0·04 ng ml^?1, 0·05 ± 0·04 ng ml^?1, 0·03 ± 0·02 ng ml^?1; Trial 2: 0·02 ± 0·04 ng ml^?1, 0·04 ± 0·03 ng ml^?1, 0·05 ± 0·06 ng ml^?1) in either trial. Very small within subject changes were not significantly correlated between the two trials (r = 0·06; P>0·05). Subsequently, short duration, high intensity exercise does not elicit a clinically relevant response in cTnI and any small alterations likely reflect the underlying biological variability of cTnI measurement within the participants.     

Acute hormonal responses following different velocities of eccentric exercise

The aim of this study was to compare the acute hormonal responses following two different eccentric exercise velocities. Seventeen healthy, untrained, young women were randomly placed into two groups to perform five sets of six maximal isokinetic eccentric actions at slow (30° s^?1) and fast (210° s^?1) velocities with 60‐s rest between sets. Growth hormone, cortisol, free and total testosterone were assessed by blood samples collected at baseline, immediately postexercise, 5, 15 and 30 min following eccentric exercise. Changes in hormonal responses over time were compared between groups, using a mixed model followed by a Tukey's post hoc test. The main findings of the present study were that the slow group showed higher growth hormone values immediately (5·08 ± 2·85 ng ml^?1, P = 0·011), 5 (5·54 ± 3·01 ng ml^?1, P = 0·004) and 15 min (4·30 ± 2·87 ng ml^?1, P = 0·021) posteccentric exercise compared with the fast group (1·39 ± 2·41 ng ml^?1, 1·34 ± 1·97 ng ml^?1 and 1·24 ± 1·87 ng ml^?1, respectively), and other hormonal responses were not different between groups (P>0·05). In conclusion, slow eccentric exercise velocity enhances more the growth hormone(GH) response than fast eccentric exercise velocity without cortisol and testosterone increases.     

The exercise heart rate profile in master athletes compared to healthy controls

Endurance exercise protects the heart via effects on autonomic control of heart rate (HR); however, its effects on HR indices in healthy middle‐aged men are unclear. This study compared HR profiles, including resting HR, increase in HR during exercise and HR recovery after exercise, in middle‐aged athletes and controls. Fifty endurance‐trained athletes and 50 controls (all male; mean age, 48·7 ± 5·8 years) performed an incremental symptom‐limited exercise treadmill test. The electrocardiographic findings and HR profiles were evaluated. Maximal O₂ uptake (52·6 ± 7·0 versus 34·8 ± 4·5 ml kg^?1 min^?1; P<0·001) and the metabolic equivalent of task (15·4 ± 1·6 versus 12·2 ± 1·5; P<0·001) were significantly higher in athletes than in controls. Resting HR was significantly lower in athletes than in controls (62·8 ± 6·7 versus 74·0 ± 10·4 beats per minute (bpm), respectively; P<0·001). Athletes showed a greater increase in HR during exercise than controls (110·1 ± 11·0 versus 88·1 ± 15·4 bpm; P<0·001); however, there was no significant between‐group difference in HR recovery at 1 min after cessation of exercise (22·9 ± 5·6 versus 21·3 ± 6·7 bpm; P = 0·20). Additionally, athletes showed a lower incidence of premature ventricular contractions (PVCs) during exercise (0·0% versus 24·0%; P<0·001). Healthy middle‐aged men participating in regular endurance exercise showed more favourable exercise HR profiles and a lower incidence of PVCs during exercise than sedentary men. These results reflect the beneficial effect of endurance training on autonomic control of the heart.     

Glucose turnover and intima media thickness of internal carotid artery in type 2 diabetes offspring

Background First‐degree offspring (OFF) of type 2 diabetic (T2DM) patients bear a ~40% lifetime risk of developing T2DM. They are insulin resistant and carry a risk of premature atherosclerosis, the extent of which can be estimated by intima media thickness (IMT) of the carotid artery (CA). Thus, this study examines parameters of glucose and lipid metabolism, insulin sensitivity, beta cell function (BCF) and IMT with their interrelationships in middle‐aged OFF. Materials and methods T2DM‐OFF (n = 18, 14f/4m, 45·6 ± 2·1 years, BMI: 26 ± 1 kg m^?2) were compared with 18 matching humans without a family history of diabetes (CON; 14f/4m, 44·5 ± 2·1 years, BMI: 24 ± 1 kg m^?2; each P > 0·30), all with normal glucose tolerance as tested by three‐hour (75 g) oral glucose tolerance tests (OGTT). Two‐hour hyperinsulinaemic (40 mU min^?1·m^?2)isoglycaemic clamp tests were performed with simultaneous measurement of endogenous glucose (D‐[6,6‐²H₂]glucose) production (EGP). IMT [internal (ICA), common CA, and bulb] were measured sonographically. BCF was assessed by Adaptation Index (AI). Results Before and during OGTT, both groups were similar in plasma glucose, insulin, C‐peptide and free fatty acids (FFA), whereas OFF showed ~30% lower (P < 0·03) fasting plasma triglycerides before OGTT. During hyperinsulinaemic clamps, insulin sensitivity was ~38% lower (P < 0·03) in OFF who showed higher plasma FFA (44 ± 9 µmol L^?1) than CON (26 ± 3 µmol L^?1, P < 0·05) after 90 min. EGP was similar in both groups. OFF had 38% (P < 0·007) reduced AI. ICA‐IMT was ~18% higher in OFF (P < 0·002), but did not correlate with insulin sensitivity. Conclusion The data obtained show middle‐aged T2DM‐OFF with normal glucose tolerance displaying reduced total insulin sensitivity and impaired beta cell function, which relates to impaired insulin‐dependent suppression of plasma FFA and increased ICA‐IMT.     

Changes in free radical generation and antioxidant capacity during ultramarathon foot race

Background Exhaustive exercise has been implicated in the generation of reactive oxygen species, resulting in oxidative stress. We studied the effect of a long‐distance, endurance exercise on oxidative stress parameters in athletes who participated in the ultramarathon race Spartathlon (246 km). Materials and methods This study included 18 runners (16 men and 2 women) aged 42·8 ± 1·4 years. Blood samples were obtained 24 h before (prerace), at the end (postrace) and 48 h after the end of the race (48 h postrace). We measured oxidative stress indices, including red cell glutathione, malonyldialdehyde and 8‐iso‐prostaglandin F_2a, as well as the total antioxidant capacity. Results 8‐Iso‐prostaglandin F_2a level increased significantly at the end of the race, compared to prerace levels (up to 914·7 ± 61·4 pg mL^?1 from 197·6 ± 8·4 pg mL^?1), and remained 2·5‐fold increased over the baseline 48 h after the race (532·0 ± 54·2 pg mL^?1, P < 0·000). The total antioxidant capacity of the athletes increased from a baseline of 289·6 ± 9·0 µmol L^?1 to 358·7 ± 11·0 µmol L^?1 immediately after the race and remained elevated 48 h later (350·6 ± 7·6 µmol L^?1) (P < 0·001). Conclusions Prolonged exercise induces a marked response of oxidative stress biomarkers, which in part is compensated by serum ability to scavenge free radicals. Whether these changes have long‐term negative effects in the organism needs further investigation.     

Impact of functional training on cardiac autonomic modulation,cardiopulmonary parameters and quality of life in healthy women

Functional training (FT) promotes benefits in various physical abilities; however, its effect on autonomic modulation, cardiorespiratory parameters and quality of life in the healthy adult population is unknown, and thus, the aim of this study was to evaluate the influence of FT on these variables in healthy young women. The study consisted of 29 women, distributed into two groups: the FT Group (FTG; n = 13; 23 ± 2·51 years; 21·90 ± 2·82 kg m^?²) and the Control Group (CG; n = 16; 20·56 ± 1·03 years; 22·12 ± 3·86 kg m^?²). The FTG performed periodized FT for 12 weeks, three times a week. The following were evaluated: autonomic modulation (heart rate variability), cardiorespiratory parameters and quality of life (SF‐36 Questionnaire). The Student's t‐test for unpaired data or the Mann–Whitney test was used to compare the differences obtained between the final moment and the initial moment of the studied groups (P<0·05). The FTG demonstrated significant improvements in quality of life and autonomic modulation (P<0·05), but not in the cardiorespiratory parameters. Functional training was able to produce improvements in autonomic modulation and quality of life.     

Positive effect of exercise training at maximal fat oxidation intensity on body composition and lipid metabolism in overweight middle‐aged women

The purpose of this study was to test the hypothesis that 10 weeks of supervised exercise training at the maximal fat oxidation (FATmax) intensity would improve important variables of body composition and lipid metabolism in overweight middle‐aged women. A longitudinal study design was employed to evaluate the effects of FATmax exercise training. Thirty women (45–59 years old; BMI 28·2 ± 1·8 kg m^?2; body fat 38·9 ± 4·1%) were randomly allocated into the Exercise and Control groups, n = 15 in each group. Body composition, FATmax, predicted VO₂max, lipid profile, plasma lipoprotein lipase activity and serum leptin concentration were measured before and after the experimental period. The Exercise group was trained at the individualized FATmax intensity, 5 days per week and 1 h per day for 10 weeks. No diet control was introduced during the experimental period for all participants. Exercise group obtained significant decreases in body mass, BMI, body fat % and abdominal fat mass, as well as the concentrations of triglycerides, serum leptin and blood glucose. The activity of lipoprotein lipase was increased in trained participants. There were no changes in these variables in the Control group. In addition, there was no significant change in daily energy intake for all participants before and after the experimental period. In conclusion, the 10‐week FATmax exercise training achieved improvements in body composition and lipid metabolism in overweight middle‐aged women. This result suggests FATmax is an effective exercise training intensity for obesity treatment.     

Lower limb vascular conductance and resting popliteal blood flow during head‐up and head‐down postural challenges

This study hypothesized that central and local reflex mechanisms affecting vascular conductance (VC) through the popliteal artery compensated for the reduction in muscle perfusion pressure (MPP) to maintain popliteal blood flow (PBF) during head‐down tilt (35? HDT), but not in head‐up tilt (45? HUT). Resting measurements were made on 15 healthy men in prone position to facilitate the access to the popliteal artery, on two separate days in random order during horizontal (HOR), HDT or HUT. In each body position, the body was supported, and the ankles were maintained in relaxed state so that there was no muscle tension, as with normal standing. Popliteal blood flow velocity and popliteal arterial diameter were measured by ultrasound, and PBF was calculated. MPP was corrected to mid‐calf from measured finger cuff pressure, and VC was estimated by dividing PBF by MPP. The MPP in HDT (48 ± 2 mmHg) was ~100mmHg less than in HUT (145 ± 2 mmHg). PBF was similar between HOR (51 ± 18 ml min^?1) and HDT (47 ± 13 ml min^?1), but was lower in HUT (30 ± 9 ml min^?1). VC was different between HDT (1·0 ± 0·3 ml min^?1 mmHg^?1), HOR (0·6 ± 0·2 ml min^?1 mmHg^?1) and HUT (0·2 ± 0·1 ml min^?1 mmHg^?1). In conclusion, the interactions of central and local regulatory mechanisms resulted in a disproportionate reduction of VC during HUT lowering PBF even though MPP was higher, while in HDT, increased VC contributed to maintain PBF at the same level as the HOR control condition.     

Acute physiological and perceptual responses to high‐load resistance exercise in hypoxia

This study assessed whether hypoxia during high‐load resistance exercise could enhance the acute physiological responses related to muscular development. Twelve trained men performed exercise in three conditions: normoxia (fraction of inspired oxygen [F_IO₂] = 21%), moderate‐level hypoxia (F_IO₂ = 16%) and high‐level hypoxia (F_IO₂ = 13%). Exercise comprised high‐load squats and deadlifts (5 × 5 using 80% of 1‐repetition maximum with 180‐s rest). Muscle oxygenation and activation were monitored during exercise. Metabolic stress was estimated via capillary blood sampling. Perceived fatigue and soreness were also quantified following exercise. While the hypoxic conditions appeared to affect muscle oxygenation, significant differences between conditions were only noted for maximal deoxyhaemoglobin in the deadlift (P = 0·009). Blood lactate concentration increased from 1·1 to 1·2 mmol l^?1 at baseline to 9·5–9·8 mmol l^?1 after squats and 10·4–10·5 mmol l^?1 after deadlifts (P≤0·001), although there were no between‐condition differences. Perceived fatigue and muscle soreness were significantly elevated immediately and at 24 h following exercise, respectively, by similar magnitudes in all conditions (P≤0·001). Muscle activation did not differ between conditions. While metabolic stress is thought to moderate muscle activation and subsequent muscular development during hypoxic resistance training, it is not augmented during traditional high‐load exercise. This may be explained by the low number of repetitions performed and the long interset rest periods employed during this training. These findings suggest that high‐load resistance training might not benefit from additional hypoxia as has been shown for low‐ and moderate‐load training.     

Influence of body adiposity on structural characteristics of skeletal muscle in men and women

The structure of skeletal muscle (SM) can be characterized by quantitative (size) and qualitative (composition) attributes, which are disparately reported to be influenced by body adiposity. This study tests the hypothesis that body adiposity exerts a systematic influence on these muscle characteristics and evaluates the possible functional implications for movements. Lower limb SM volume (VSM) and attenuation (ATTSM), an inverse measure of lipid infiltration in muscle, were determined with computed tomography in 21 men (BMI = 21–36 kg m^?2; age = 31–71 years.) and 18 women (BMI = 19–35 kg m^?2; age = 32–76 years.). After adjusting for age, a multivariate regression analysis revealed that body adiposity positively correlated (P<0·05–0·001) with absolute VSM and cross‐sectional area (CSA) in both genders, while VSM per unit body mass (VSM/BM) decreased with adiposity (P<0·001) in women and was constant in men. ATTSM was higher in men (P<0·05) and decreased (P<0·05) with adiposity in both genders. The product of ATTSM by average muscle CSA (predictor of maximal strength) and by VSM/BM (predictor of maximal dynamic performance) was lower in women (P<0·001) and was reduced by age in both genders (P<0·05–0·01), while obesity had a negative effect (P<0·001) only on the predictor of performance. In conclusion, body adiposity significantly increases SM size and reduces ATTSM. Structural indicators accounting for both quantitative and qualitative characteristics of SM may be useful predictors of the effects of obesity on motor function at different ages. With rising body adiposity and advancing age, women appear mostly affected by the decline of SM features relevant for motor performance.     

Effects of walking with blood flow restriction on limb venous compliance in elderly subjects

Venous compliance declines with age and improves with chronic endurance exercise. KAATSU, an exercise combined with blood flow restriction (BFR), is a unique training method for promoting muscle hypertrophy and strength gains by using low‐intensity resistance exercises or walking. This method also induces pooling of venous blood in the legs. Therefore, we hypothesized that slow walking with BFR may affect limb venous compliance and examined the influence of 6 weeks of walking with BFR on venous compliance in older women. Sixteen women aged 59–78 years were partially randomized into either a slow walking with BFR group (n = 9, BFR walk group) or a non‐exercising control group (n = 7, control group). The BFR walk group performed 20‐min treadmill slow walking (67 m min^?1), 5 days per week for 6 weeks. Before (pre) and after (post) those 6 weeks, venous properties were assessed using strain gauge venous occlusion plethysmography. After 6 weeks, leg venous compliance increased significantly in the BFR walk group (pre: 0·0518 ± 0·0084, post: 0·0619 ± 0·0150 ml 100 ml^?1 mmHg^?1, P<0·05), and maximal venous outflow (MVO) at 80 mmHg also increased significantly after the BFR walk group trained for 6 weeks (pre: 55·3 ± 15·6, post: 67·1 ± 18·9 ml 100 ml^?1 min^?1, P<0·01), but no significant differences were observed in venous compliance and MVO in the control group. In addition, there was no significant change in arm compliance in the BFR walk group. In conclusion, this study provides the first evidence that 6 weeks of walking exercise with BFR may improve limb venous compliance in untrained elder female subjects.     

Utility of ultrasound for body fat assessment: validity and reliability compared to a multicompartment criterion

Measurement of body composition to assess health risk and prevention is expanding. Accurate portable techniques are needed to facilitate use in clinical settings. This study evaluated the accuracy and repeatability of a portable ultrasound (US) in comparison with a four‐compartment criterion for per cent body fat (%Fat) in overweight/obese adults. Fifty‐one participants (mean ± SD; age: 37·2 ± 11·3 years; BMI: 31·6 ± 5·2 kg m^?2) were measured for %Fat using US (GE Logiq‐e) and skinfolds. A subset of 36 participants completed a second day of the same measurements, to determine reliability. US and skinfold %Fat were calculated using the seven‐site Jackson–Pollock equation. The Wang 4C model was used as the criterion method for %Fat. Compared to a gold standard criterion, US %Fat (36·4 ± 11·8%; P = 0·001; standard error of estimate [SEE] = 3·5%) was significantly higher than the criterion (33·0 ± 8·0%), but not different than skinfolds (35·3 ± 5·9%; P = 0·836; SEE = 4·5%). US resulted in good reliability, with no significant differences from Day 1 (39·95 ± 15·37%) to Day 2 (40·01 ± 15·42%). Relative consistency was 0·96, and standard error of measure was 0·94%. Although US overpredicted %Fat compared to the criterion, a moderate SEE for US is suggestive of a practical assessment tool in overweight individuals. %Fat differences reported from these field‐based techniques are less than reported by other single‐measurement laboratory methods and therefore may have utility in a clinical setting. This technique may also accurately track changes.     

Fatigue and rapid hamstring/quadriceps force capacity in professional soccer players

The aim of this study was to investigate the effect of fatigue induced by an exhaustive laboratory‐based soccer‐specific exercise on different hamstrings/quadriceps (H:Q) ratios of soccer players. Twenty‐two male professional soccer players (23·1 ± 3·4 year) performed maximal eccentric (ecc) and concentric (con) contractions for knee extensors (KE) and flexors (KF) at 60° s^?1 and 180° s^?1 to assess conventional (H_con:Q_con) and functional (H_ecc:Q_con) ratios. Additionally, they performed maximal voluntary isometric contraction for KE and KF, from which the maximal muscle strength, rate of force development (RFD) and RFD H:Q strength ratio (RFDH:Q) were extracted. Thereafter, subjects were performed an exhaustive laboratory‐based soccer‐specific exercise and a posttest similar to the pretest. There was significant reduction in H_con:Q_con (0·60 ± 0·06 versus 0·58 ± 0·06, P<0·05) and in H_ecc:Q_con (1·29 ± 0·2 versus 1·16 ± 0·2, P<0·01) after the soccer‐specific exercise. However, no significant difference between Pre and Post exercise conditions was found for RFDH:Q at 0–50 (0·53 ± 0·23 versus 0·57 ± 0·24, P>0·05) and 0–100 ms (0·53 ± 0·17 versus 0·55 ± 0·17, P>0·05). In conclusion, H:Q strength ratios based on peak force values are more affected by fatigue than RFDH:Q obtained during early contraction phase. Thus, fatigue induced by soccer‐specific intermittent protocol seems not reduce the potential for knee joint stabilization during the initial phase of voluntary muscle contraction.     

Simultaneous quantification of myocardial perfusion,oxidative metabolism,cardiac efficiency and pump function at rest and during supine bicycle exercise using 1‐11C‐acetate PET – a pilot study

Background: PET using 1‐¹¹C‐acetate (ACE‐PET) applied at rest is used for measuring absolute myocardial blood flow (MBF) and oxidative metabolic rate (k_mono). We evaluated the feasibility of quantitative ACE‐PET during exercise. Methods: Five endurance athletes underwent dynamic PET scanning at rest and during supine bicycle stress. Exercise was maintained at a workload of 120 Watt for 17 min. The rate‐pressure product (RPP) was recorded repeatedly. MBF, k_mono in left (LV) and right (RV) ventricular wall, cardiac output (CO), cardiac efficiency and a lung uptake value reflecting left heart diastolic pressures were calculated from the PET data using previously validated models. Results: MBF increased from 0·71 ± 0·17 to 2·48 ± 0·25 ml min^?1 per ml, LV‐k_mono from 0·050 ± 0·005 to 0·146 ± 0·021 min^?1, RV‐k_mono from 0·023 + 0·006 to 0·087 + 0·014 min^‐1, RPP from 4·7 ± 0·8 to 13·2 ± 1·4 mmHg × min^?1 × 10³ and Cardiac Output from 5·2 ± 1·1 to 12·3 ± 1·2 l min ^?1 (all P < 0·001). Cardiac efficiency was unchanged (P = 0·99). Lung uptake decreased from 1·1 ± 0·2 to 0·6 ± 0·1 ml g^?1 (P < 0·001). Discussion: A number of important parameters related to cardiac function can be quantified non‐invasively and simultaneously with a short scanning protocol during steady state supine bicycling. This might open up new opportunities for studies of the integrated cardiac physiology in health and early asymptomatic disease.     

Head‐to‐head comparison between Actigraph 7164 and GT1M accelerometers in adolescents

We compared, head‐to‐head, the old generation Actigraph model 7164 with the new generation Actigraph GT1M accelerometer. A total of 15 randomly selected teenagers (eight girls and seven boys) were investigated. They performed a treadmill test wearing the two kinds of accelerometers around the waist simultaneously. The treadmill test consisted of three different levels of speed 4, 6 and 8 km h^?1 for four consecutive minutes. Accelerometer counts per 1 sec epoch for the Actigraph GT1M versus the Actigraph 7164 were at 4 km h^?1 21·6 ± 12·9 versus 26·5 ± 11·5 counts, at 6 km h^?1 56·0 ± 23·2 versus 62·9 ± 25·6 counts and at 8 km h^?1 142·6 ± 37·2 versus 156·4 ± 34·9 counts (P<0·01 for all levels of speed). Data from the old generation Actigraph 7164 and the new generation Actigraph GT1M accelerometers differ, where the Actigraph GT1M generates 10‐23% lower values. Correction equation for Actigraph GT1M was Actigraph 7164 = 5·2484 +  Actigraph GT1M counts × 1·0448. These results need to be taken into consideration when using these devices.