Eccentric cycling emphasising a low cardiopulmonary demand increases leg strength equivalent to workload matched concentric cycling in middle age sedentary males.

OBJECTIVES: This study determined if eccentric endurance cycling, eliciting a low cardiovascular demand, could stimulate muscle strength adaptations in sedentary middle-aged males. DESIGN: Twenty-four middle-aged sedentary males were allocated to concentric (CON) or matched workload eccentric (ECC) cycling (60% peak concentric workload) according to their maximal voluntary isometric quadriceps strength. METHODS: Seventeen participants [42.7±8.3 years, BMI 28.6±5.2, peak oxygen consumption [30.5±5.8mLkg-1min-1] completed 8 weeks (2 sessions per week) of CON (n=8) or ECC (n=9) cycle training. Incline leg press (6RM), maximal voluntary isometric contraction (MVIC) torque of the quadriceps and peak oxygen consumption were measured at baseline and 8 weeks. RESULTS: Eccentric cycle training resulted in low cardiovascular demand (CON 154±2; ECC 95±3bmin-1P<0.05) and ratings of perceived exertion (CON 14.9±0.3; ECC 9.5±0.3/20 P<0.05). Peak oxygen consumption improved within the CON group (Baseline 27.4±2.1; 8 weeks: 30.0±1.7mLkg-1min-1P<0.05) and not within the ECC group (Baseline 33.2±1.5; 8 weeks 33.3±1.6mLkg-1min-1) following training. 6RM (CON 176±20; ECC 192±11kg) and MVIC (CON 199±25; ECC 199±25Nm) strength were equivalent at baseline (P>0.05). Both groups significantly increased 6RM (CON 13.0±3.0; ECC 10.7±3.2%) and MVIC (CON 12.9±4.3; ECC 18.8±3.0%) relative to their own baseline (P<0.05). Therefore, improved leg strength was equivalent between CON and ECC groups despite the varied training (P>0.05). CONCLUSIONS: In sedentary middle age males, eccentric endurance cycling with a low cardiovascular demand, increased both quadriceps isometric and 6RM strength comparable to a matched workload concentric cycling program.

DHA-rich Fish Oil Increases the Omega-3 Index and Lowers the Oxygen Cost of Physiologically Stressful Cycling in Trained Individuals.

Dietary fish oil, providing docosahexaenoic acid (DHA) modulates oxygen consumption and fatigue in animal models. However, in humans predominately supplemented with high eicosapentaenoic acid (EPA), there is no evidence of endurance performance enhancement. Therefore, this study examined if DHA-rich fish oil could improve repeated bouts of physiologically stressful cycling and a subsequent time trial in a state of fatigue. Twenty-six trained males took part in a double-blind study and were supplemented with either 2 × 1g/day soy oil, Control) or DHA-rich tuna fish oil (Nu-Mega) (FO) (560mg DHA / 140mg eicosapentaenoic acid (EPA), for 8 weeks. Maximal cycling power (3 × 6s), isometric quadriceps strength (MVC), Wingate cycling protocol (6 × 30s) and a 5min cycling time-trial were assessed at baseline and eight weeks. The Omega-3 Index was not different at baseline (Control: 4.2 ± 0.2; FO: 4.7 ± 0.2%) and increased in the FO group after eight weeks (Control: 3.9 ± 0.2; FO: 6.3 ± 0.3%, p < .01). There was no effect of DHA-rich fish oil on power output of maximal 6s cycle sprinting (Control: Pre 1100 ± 49 Post 1067 ± 51; FO: Pre 1070 ± 46 Post 1042 ± 46W), during 5min time trail (Control: Pre 267 ± 19 Post 278 ± 20; FO: Pre 253 ± 16 Post 265 ± 16 W) or maximal voluntary contraction force (Control: Pre 273 ± 19 Post 251 ± 19; FO: Pre 287 ± 17 Post 283 ± 16 Nm). Nevertheless, relative oxygen consumption was reduced the FO group during the cycling time trial (Control: -23 ± 26; FO: -154 ± 59ml O2/min/100W p < .05) suggesting improved economy of cycling. We conclude that DHA-rich fish oil, successful at elevating the Omega-3 Index, and reflective of skeletal muscle membrane incorporation, can modulate oxygen consumption during intense exercise.

Intrinsic heart rate recovery after dynamic exercise is improved with an increased omega-3 index in healthy males.

Dietary fish consumption contributes to a reduced risk of cardiac mortality. In the present study, the effect of low-dose fish oil (FO) supplementation on heart rate (HR) response to intense exercise and recovery was investigated in physically fit males. The subjects (n 26) were supplemented (double-blind, parallel design) with (2 × 1 g/d) soya bean oil (control) or tuna FO providing the long-chain n-3 PUFA DHA (560 mg) and EPA (140 mg). Erythrocyte omega-3 index (%EPA+DHA), HR, HR variability and HR recovery were analysed during rest, intense exercise and recovery at baseline and after 8 weeks of supplementation. The mean erythrocyte omega-3 index, which did not differ between the groups at baseline (control 4.2 (sem 0.2), n 13; FO 4.7 (sem 0.2), n 13), remained unchanged in the control group (3.9 (sem 0.2)), but increased in the FO group (6.3 (sem 0.3); P< 0.01). The mean HR during supine resting conditions (control 56 (sem 10); FO 59 (sem 9)) was not affected by FO supplementation. Poincaré analysis of HR variability at rest exhibited a decreasing trend in parasympathetic activity in the FO group (SD1 (standard deviation of points perpendicular to the axis of line of identity)/SD2 (standard deviation of points along the axis of line of identity): control 0.02 (sem 0.01); FO - 0.05 (sem 0.02); P= 0.18). Peak HR was not affected by supplementation. However, during submaximal exercise over 5 min, fewer total heart beats were recorded in the FO group (-22 (sem 6) ( = -4.5 beats/min)), but not in the control group (+1 (sem 4)) (P< 0.05). Supine HR recovery (half-time) after cycling was significantly faster after FO supplementation (control - 0.4 (sem 1.2) s; FO - 8.0 (sem 1.7) s; P< 0.05). A low intake of FO increased the omega-3 index and reduced the mean exercise HR and improved HR recovery without compromising the peak HR. A direct influence of DHA via reductions in the cardiac intrinsic beat rate was balanced by a reciprocal decrease in vagal tone.

Observations on saliva osmolality during progressive dehydration and partial rehydration.

A need exists to identify dehydrated individuals under stressful settings beyond the laboratory. A predictive index based on changes in saliva osmolality has been proposed, and its efficacy and sensitivity was appraised across mass (water) losses from 1 to 7%. Twelve euhydrated males [serum osmolality: 286.1 mOsm kg(-1) H(2)O (SD 4.3)] completed three exercise- and heat-induced dehydration trials (35.6°C, 56% relative humidity): 7% dehydration (6.15 h), 3% dehydration (with 60% fluid replacement: 2.37 h), repeat 7% dehydration (5.27 h). Expectorated saliva osmolality, measured at baseline and at each 1% mass change, was used to predict instantaneous hydration state relative to mass losses of 3 and 6%. Saliva osmolality increased linearly with dehydration, although its basal osmolality and its rate of change varied among and within subjects across trials. Receiver operating characteristic curves indicated a good predictive power for saliva osmolality when used with two, single-threshold cutoffs to differentiate between hydrated and dehydrated individuals (area under curve: 3% cutoff = 0.868, 6% cutoff = 0.831). However, when analysed using a double-threshold detection technique (3 and 6%), as might be used in a field-based monitor, <50% of the osmolality data could correctly identify individuals who exceeded 3% dehydration. Indeed, within the 3-6% dehydration range, its sensitivity was 64%, while beyond 6% dehydration, this fell to 42%. Therefore, while expectorated saliva osmolality tracked mass losses within individuals, its large intra- and inter-individual variability limited its predictive power and sensitivity, rendering its utility questionable within a universal dehydration monitor.

Consumption of resistant starch decreases postprandial lipogenesis in white adipose tissue of the rat.

Chronic consumption of diets high in resistant starch (RS) leads to reduced fat cell size compared to diets high in digestible starch (DS) in rats and increases total and meal fat oxidation in humans. The aim of the present study was to examine the rate of lipogenesis in key lipogenic organs following a high RS or DS meal. Following an overnight fast, male Wistar rats ingested a meal with an RS content of 2% or 30% of total carbohydrate and were then administered an i.p bolus of 50 muCi 3H2O either immediately or 1 hour post-meal. One hour following tracer administration, rats were sacrificed, a blood sample collected, and the liver, white adipose tissue (WAT), and gastrocnemius muscle excised and frozen until assayed for total 3H-lipid and 3H-glycogen content. Plasma triglyceride and NEFA concentrations and 3H-glycogen content did not differ between groups. In all tissues, except the liver, there was a trend for the rate of lipogenesis to be higher in the DS group than the RS group which reached significance only in WAT at 1 h (p < 0.01). On a whole body level, this attenuation of fat deposition in WAT in response to a RS diet could be significant for the prevention of weight gain in the long-term.

Cooking attenuates the ability of high-amylose meals to reduce plasma insulin concentrations in rats.

Postprandial glycaemic control is important in the prevention and therapy of type 2 diabetes and related diseases. Agents that may reduce postprandial glycaemia and/or insulinaemia, such as consumption of high-amylose foods, are considered beneficial; however, little is known about the dose-response relationship and the effects of cooking. The aim of the present study was to define the dose-response curve for postprandial glycaemic and insulinaemic excursions following meals of different amylose content and to compare the dose-response curves for meals containing cooked and uncooked starches. Following an overnight fast, rats ingested a test meal and blood was sampled over 2 h. The meal was given at 1.0 g carbohydrate/kg body weight, with an amylose content of 0, 270, 600 or 850 g/kg total starch. The area under the glucose curve did not differ under any condition investigated. For the uncooked-starch diets, area under the insulin curve was higher for the 0 g amylose/kg total starch meal than all other meals (P=0.0001). For the cooked-starch diets, area under the insulin curve was higher in the 0 than the 600 and 850 g amylose/kg total starch groups (P<0.01), but did not differ from the 270 amylose/kg total starch group. These results suggest that even a relatively small proportion of uncooked amylose (270 g/kg total starch) is sufficient to achieve a maximal attenuating effect on postprandial insulin concentrations as compared with 0 g amylose/kg total starch. Following cooking, however, a much higher proportion of amylose (>or=600 g/kg total starch) is needed to achieve a similar effect.