Effect of different rest interval lengths of resistance exercise on lipid peroxidation and creatine kinase responses

The purpose of this study was to determine the effects of two resistance exercise (RE) protocols with different rest intervals between sets on oxidative stress and exercise-induced muscle damage. For this purpose, twenty untrained males voluntarily participated in the research and were randomly assigned to one of two resistance exercise groups: a) a shorter inter-set rest interval of 90 second (RI-90; n=10); or b) a longer rest interval of 180 second (RI-180; n=10). Resistance exercise in both groups consisted of chest press (CP), “lat” pull down (LP), leg extension (LE), leg curl (LC), and back squat (BS) exercises; these were done at a load of six repetitions maximum (6 RM). Blood samples were collected from the antecubital vein preexercise, immediately post-exercise, 6, 24, and 48 hours post-exercise, and analyzed for malondiadehyde (MDA) concentration and creatine kinase (CK) activity. The results indicated that both RI-90 and RI-180 caused significant changes in the MDA response (p=.003 and p=.036 in RI-90 and RI-180, respectively); MDA significantly increased six hours post-resistance exercise in both groups. Creatine kinase activity significantly increased at the 24-hour point post-exercise in both groups and continued for 48 hours postexercise (p=.000 for RI-90 and RI-180). There was no significant difference between corresponding MDA and CK values of two groups. We conclude that the rest interval between sets of resistance exercise does not affect oxidative stress and myocellular damage

Random and ordered phases of off-lattice rhombus tiles

We study the covering of the plane by non-overlapping rhombus tiles, a problem well-studied only in the limiting case of dimer coverings of regular lattices. We go beyond this limit by allowing tiles to take any position and orientation on the plane, to be of irregular shape, and to possess different types of attractive interactions. Using extensive numerical simulations we show that at large tile densities there is a phase transition from a fluid of rhombus tiles to a solid packing with broken rotational symmetry. We observe self-assembly of broken-symmetry phases, even at low densities, in the presence of attractive tile-tile interactions. Depending on tile shape and interactions the solid phase can be random, possessing critical orientational fluctuations, or crystalline. Our results suggest strategies for controlling tiling order in experiments involving `molecular rhombi'.Comment: Supp. Info. and version with high-res figures at http://nanotheory.lbl.gov/people/rhombus_paper/rhombus.htm

Mechanical Work and Physiological Responses to Simulated Flat Water Slalom Kayaking

The purpose of this study was to assess the physical work demand in relation to metrics of force and subsequent physiological response to a simulated flatwater slalom competition. Eight New Zealand team members completed a standard incremental step-test to ascertain power:oxygen consumption relationship. This was followed by a simulated race run where breath-by-breath analysis along with force and power data logged at 50 Hz to determine stroke length, impulse, peak force, time to peak force, and rate of peak force per stroke. Physiological response to negotiating a flatwater slalom course was greater than straight-line paddling (36.89 ± 2.01 vs. 32.17 ± 1.97 ml⋅kg-1⋅min-1, p = 0.0065) at the same power output. Mean power output for the duration of the simulated race (91.63 ± 7.19 s) was 203.8 ± 45.0 W, incurring an oxygen deficit of 1.386 ± 0.541 L⋅min-1 translating to an overall anaerobic contribution of 32 ± 18% and aerobic contribution of 68 ± 18%. Moderate to strong relationships between time duration and stroke peak force (R2 = 0.354, R2 = 0.485) and rate of peak force development (R2 = 0.345, R2 = 0.426) but not for stroke length (R2 = 0.022, R2 = 0.012), impulse (R2 = 0.088, R2 = 0.097) or time to peak force (R2 = 0.001, R2 = 0.0001) for left and right strokes, respectively. The number of propulsive (<0.6 s) strokes outweighed turning/driving (>0.6 s) strokes with a ratio of 94:6%. Longer stroke duration was significantly correlated to greater impulse (R2 = 0.507, p < 0.0001) and time to peak force (R2 = 0.851, p < 0.0001), but a lower rate of force development (R2 = 0.107, p < 0.0001). The results show that a flatwater slalom under simulated race conditions entails initial supra-maximal (anaerobic) work rate with a subsequent transition to one associated with maximal aerobic capacity. Inability to sustain work done and the subsequent decline in peak force and force profile per stroke requires further research regarding strategies to enhance performance

Učinci suplementacije omega 3 masnim kiselinama na razinu oksidativnih markera u krvi, mišićno oštećenje i upalne biljege nakon treninga s opterećenjem u mladih sportaša

The present study was conducted to assess the effect of dietary omega-3 fatty acid supplementation on the levels of oxidative stress, muscle damage, and inflammatory markers after acute resistance exercise in young athletes. In a randomized double-blind design, twenty subjects were divided into two equal groups; each subject receiving three capsules per day (3000 mg) of either omega-3 or a placebo for seven days. All subjects underwent high intensity acute resistance exercise. Venous blood samples were collected one week prior to the exercise, immediately pre-exercise, and 24 hours post exercise. Malondiadehyde (MDA), plasma total antioxidant capacity (FRAP), C-reactive protein (CRP), creatine kinase (CK), and lactate dehydrogenase (LDH) were measured in the serum. MDA, CRP and CK concentrations were significantly higher 24 hours post exercise in the placebo versus the omega-3 group (p=.005). The mean of total antioxidant capacity in both groups showed no significant differences immediately pre-exercise and 24 hours post exercise (p>.005). LDH activity was significantly higher 24 hours post exercise in both groups (p=0,005). Aktivnost LDH bila je statistički značajno viša 24 sata nakon vježbanja u obje grupe (p<0,05). Rezultati ovog istraživanja pokazuju da visokointenzivne vježbe s opterećenjem izazivaju oksidativni stres, sistemske upalne procese i povećavaju razinu pokazatelja staničnih oštećenja u sportaša. Ipak, sedam dana suplementacije omega 3 masnim kiselinama mogu smanjiti navedene učinke treninga

Nicotine Supplementation Does Not Influence Performance of a 1h Cycling Time-Trial in Trained Males

The use of nicotine amongst professional and elite athletes is high, with anecdotal evidence indicating increased prevalence amongst cycling sports. However, previous investigations into its effects on performance have not used high-validity or -reliability protocols nor trained cyclists. Therefore, the present study determined whether nicotine administration proved ergogenic during a ∼1 h self-paced cycling time-trial (TT). Ten well-trained male cyclists (34 ± 9 years; 71 ± 8 kg; O2max: 71 ± 6 ml ⋅ kg−1 ⋅ min−1) completed three work-dependent TT following ∼30 min administration of 2 mg nicotine gum (GUM), ∼10 h administration of 7 mg ⋅ 24 h−1 nicotine patch (PAT) or color- and flavor-matched placebos (PLA) in a randomized, crossover, and double blind design. Measures of nicotine’s primary metabolite (cotinine), core body temperature, heart rate, blood biochemistry (pH, HCO3−, La−) and Borg’s rating of perceived exertion (RPE) accompanied performance measures of time and power output. Plasma concentrations of cotinine were highest for PAT, followed by GUM, then PLA, respectively (p &lt; 0.01). GUM and PAT resulted in no significant improvement in performance time compared to PLA (62.9 ± 4.1 min, 62.6 ± 4.5 min, and 63.3 ± 4.1 min, respectively; p = 0.73), with mean power outputs of 264 ± 31, 265 ± 32, and 263 ± 33 W, respectively (p = 0.74). Core body temperature was similar between trials (p = 0.33) whilst HR averaged 170 ± 10, 170 ± 11, and 171 ± 11 beats ⋅ min−1 (p = 0.60) for GUM, PAT, and PLA, respectively. There were no differences between trials for any blood biochemistry (all p &gt; 0.46) or RPE with mean values of 16.7 ± 0.9, 16.8 ± 0.7, and 16.8 ± 0.8 (p = 0.89) for GUM, PAT, and PLA, respectively. In conclusion: (i) nicotine administration, whether via gum or transdermal patch, did not exert an ergogenic or ergolytic effect on self-paced cycling performance of ∼1 h; (ii) systemic delivery of nicotine was greatest when using a transdermal patch; and (iii) nicotine administration did not alter any of the psycho-physiological measures observed

The Efficacy of Ingesting Water on Thermoregulatory Responses and Running Performance in a Warm-Humid Condition

The understanding that fluid ingestion attenuates thermoregulatory and circulatory stress during exercise in the heat was based on studies conducted in relatively dry (∼50% RH) environments. It remains undetermined whether similar effects occur during exercise in a warm and more humid environment, where evaporative capacity is reduced. Nine well-trained, unacclimatised male runners were randomly assigned to perform four experimental trials where they ran for 60 min at an intensity of 70% VO2max followed by an incremental exercise test until volitional exhaustion. The four trials consisted of non-fluid ingestion (NF) and fluid ingestion (FI) in a warm-dry (WD) and warm-humid condition (WH). Time to exhaustion (TTE), body temperature (Tb), whole body sweat rate, partitional calorimetry measures, heart rate and plasma volume were recorded during exercise. There was no significant difference in Tb following 60 min of exercise in FI and NF trial within both WD (37.3°C ± 0.4 vs. 37.4°C ± 0.3; p &gt; 0.05) and WH conditions (38.0°C ± 0.4 vs. 38.1°C ± 0.4; p &gt; 0.05). The TTE was similar between FI and NF trials in both WH and WD, whereas exercise capacity was significantly shorter in WH than WD (9.1 ± 2.8 min vs. 12.7 ± 2.4 min, respectively; p = 0.01). Fluid ingestion failed to provide any ergogenic benefit in attenuating thermoregulatory and circulatory stress during exercise in the WH and WD conditions. Consequently, exercise performance was not enhanced with fluid ingestion in the warm-humid condition, although the humid environment detrimentally affected exercise endurance

Indirect measures of substrate utilisation following exercise-induced muscle damage

This study investigated whether exercise-induced muscle damage (EIMD) resulted in changes to whole-body substrate utilisation during exercise performed during the subsequent 48 hours. Eight males (31 ± 6 years) performed 30 minutes of bench-stepping exercise. One leg performed eccentric contractions (Ecc) by lowering the body whilst the control leg performed concentric contractions (Con) by raising the body. On the two days following bench-stepping exercise participants performed measures of muscle function on an isokinetic dynamometer and undertook a bout of one leg cycling exercise, at two differing workloads, with the first workload (WL1) at 1.5 ± 0.25 W/kg and the second workload (WL2) at 1.8 ± 0.25 W/kg with each leg. Expired respiratory gases were collected during cycling to estimate whole body substrate utilisation. There were significant decrements in measures of muscular performance (isometric force, concentric and eccentric torque) and increased perception of soreness in Ecc compared with Con (P < 0.05). The effect of the Ecc treatment on substrate utilisation during one-legged cycling revealed a significant trial × time interaction with higher rates of CHO oxidation in the Ecc condition compared with Con that were further increased 48 hours later (P = 0.02). A significant treatment × time × effort interaction (P < 0.01) indicated the effect of the treatment altered as workload increased with higher rates of CHO oxidation occurring in WL2. This is consistent with greater reliance upon muscle glycogen. Suggesting that in EIMD, reductions in strength and increased feelings of soreness can be associated with greater reliance upon intramuscular CHO oxidation, than lipid, during subsequent concentric work