Acute physiological and perceptual responses to moderate intensity cycling with different levels of blood flow restriction

The aim of this study was to compare: i) the physiological and perceptual responses of low-load exercise [(moderate intensity exercise (MI)] with different levels of blood flow restriction (BFR), and ii) MI with BFR on the bike with high intensity (HI) exercise without BFR. The protocol involved large muscle mass exercise at different levels of BFR, and this differentiates our study from others. Twenty-one moderately trained males (age: 24.6 ± 2.4 years; VO_2peak: 47.2 ± 7.0 ml^.kg^-1.min^-1, mean ± sd) performed one maximal graded exercise test and seven 5-min constant-load cycling bouts. Six bouts were at MI [40% _peak power (P_peak), 60%VO_2peak], one without BFR and five with different levels of BFR (40%, 50%, 60%, 70%, 80% of estimated arterial occlusion pressure). The HI bout (70%P_peak, 90%VO_2peak) was without BFR. Oxygen uptake (VO₂), heart rate (HR), blood lactate (BLa), rate of perceived exertion (RPE), and tissue oxygen saturation (TSI) were recorded. Regardless of pressure, HR, BLa and RPE during MI-BFR were higher compared to MI (p < 0.05, ES: moderate to very large), and TSI reduction was greater in MI-BFR than MI (p < 0.05, ES: moderate to large). The responses of VO₂, HR, BLa, RPE and TSI induced by the different levels of BFR in MI-BFR were similar. Regardless of pressure, the responses of VO₂, HR, BLa and RPE induced by MI-BFR were lower than HI (p < 0.05), except for TSI. TSI change was similar between MI-BFR and HI. It appears that BFR equal to 40% of arterial occlusion pressure is sufficient to reduce TSI when exercising with a large muscle mass.     

Nutritional and physiological responses of finishing pigs exposed to a permanent heat exposure during three weeks

The aim of the current study was to investigate the effect of a permanent heat exposure during 21 days on pig performance, nutrient digestibility, physiological response and key enzyme of skeletal muscle energy metabolism. Twenty-four male finishing pigs (crossbreed castrates, 79.0 ± 1.50 kg body weight) were allocated to three groups (n = 8): (1) Control (ambient temperature (AT) 22°C, ad libitum feeding), (2) Group HE (AT 30°C, ad libitum feeding) and (3) Group PF (AT 22°C, pair-fed to Group HE). The permanent heat exposure decreased feed intake (p < 0.01), daily body weight gain (p < 0.05) and the digestibility of gross energy, dry matter, crude protein and ash (p < 0.05); rectal temperature and respiration rate were significantly increased (p < 0.01). The levels of plasma cortisol, creatine kinase and lactate dehydrogenase were also significantly increased in Group HE (p < 0.05). Furthermore, the heat exposure changed intracellular energy metabolism, where the AMP-activated protein kinase was activated (p = 0.02). This was combined with changes in parameters of glycolysis such as an accumulation of lactic acid (p = 0.02) and a drop of pH_24?h (p = 0.02), an increase of hexokinase and pyruvate kinase activity (p < 0.01) and, finally, the maturation process of post mortem muscle was influenced. Due to pair-feeding it was possible to evaluate the effects of heat exposure, which were not dependent on reduced feed intake. Such effects were, e.g., reduced nutrient digestibility and changed activities of several enzymes in muscle and blood serum.     

Physiologic responses during indoor cycling

During the last decade, there has been active interest in indoor cycling (e.g., spinning) as a method of choreographed group exercise. Recent studies have suggested that exercise intensity during indoor cycling may be quite high and may transiently exceed Vo2max. This study sought to confirm these findings, as the apparent high intensity of indoor cycling has implications for both the efficacy and the risk of indoor cycling as an exercise method. Twenty healthy female students performed an incremental exercise test to define Vo2max and performed 2 videotaped indoor exercise classes lasting 45 minutes and 35 minutes. Vo2, heart rate (HR), and rating of perceived exertion (RPE) were measured during the indoor cycling classes, with Vo2 data integrated in 30-second intervals. The mean %Vo2max during the indoor cycling classes was modest (74 +/- 14% Vo2max and 66 +/- 14%Vo2max, respectively). However, 52% and 35% of the time during the 45- and 35-minute classes was spent at intensities greater than the ventilatory threshold (VT). The HR response indicated that 35% and 38% of the session time was above the HR associated with VT. In 10 of the 40 exercise sessions, there were segments in which the momentary Vo2 exceeded Vo2max observed during incremental testing, and the cumulative time with exercise intensity greater than Vo2max ranged from 0.5 to 14.0 minutes. It can be concluded that although the intensity of indoor cycling in healthy, physically active women is moderate, there are frequent observations of transient values of Vo2 exceeding Vo2max, and a substantial portion of the exercise bouts at intensities greater than VT. As such, the data suggest that indoor cycling must be considered a high-intensity exercise mode of exercise training, which has implications for both efficacy and risk.     

Effects of sodium bicarbonate ingestion on performance and perceptual responses in a laboratory-simulated BMX cycling qualification series

The objective of this study was to examine the effect of sodium bicarbonate (NaHCO3-) ingestion on performance and perceptual responses in a laboratory-simulated bicycle motocross (BMX) qualification series. Nine elite BMX riders volunteered to participate in this study. After familiarization, subjects undertook two trials involving repeated sprints (3 x Wingate tests [WTs] separated by 30 minutes of recovery; WT1, WT2, WT3). Ninety minutes before each trial, subjects ingested either NaHCO3- or placebo in a counterbalanced, randomly assigned, double-blind manner. Each trial was separated by 4 days. Performance variables of peak power, mean power, time to peak power, and fatigue index were calculated for each sprint. Ratings of perceived exertion were obtained after each sprint, and ratings of perceived readiness were obtained before each sprint. No significant differences were observed in performance variables between successive sprints or between trials. For the NaHCO3- trial, peak blood lactate during recovery was greater after WT2 (p < 0.05) and tended to be greater after WT3 (p = 0.07), and ratings of perceived exertion were not influenced. However, improved ratings of perceived readiness were observed before WT2 and WT3 (p < 0.05). In conclusion, NaHCO3- ingestion had no effect on performance and RPE during a series of three WT simulating a BMX qualification series, possibly because of the short duration of each effort and the long recovery time used between the three WTs. On the contrary, NaHCO3- ingestion improved perceived readiness before each WT.     

A comparative analysis of physiological responses at submaximal workloads during different laboratory simulations of field cycling

The purpose of this study was to evaluate the relationships between heart rate (f_c), oxygen consumption (VO₂), peak force and average force developed at the crank in response to submaximal exercise employing a racing bicycle which was attached to an ergometer (RE), ridden on a treadmill (TC) and ridden on a 400-m track (FC). Eight male trained competitive cyclists rode at three pre-determined work intensities set at a proportion of their maximal oxygen consumption (VO_2max): (1) below lactate threshold [work load that produces a (VO₂) which is 10% less than the lactate threshold VO2 (sub-LT)], (2) lactate threshold VO₂ (LT), and (3) above lactate threshold [workload that produces a VO₂ which is 10% greater than lactate threshold VO₂ (supra-LT)], and equated across exercise modes on the basis off_c. Voltage signals from the crank arm were recorded as FM signals for subsequent representation of peak and average force. Open circuit VO₂ measurements were done in the field by Douglas bag gas collection and in the laboratory by automated gas collection and analysis.f_c was recorded with a telemeter (Polar Electro Sport Tester, PE3000). Significant differences (P < 0.05) were observed: (1) in VO₂ between FC and both laboratory conditions at sub-LT intensity and LT intensities, (2) in peak force between FC and TC at sub-LT intensity, (3) in average force between FC and RE at sub-LT. No significant differences were demonstrated at supra-LT intensity for VO₂. Similarly no significant differences were observed in peak and average force for either LT or supra-LT intensities. These data indicate that equating work intensities on the basis off_c measured in laboratory conditions would overestimate the VO₂ which would be generated in the field and conversely, that usingf_c measured in the laboratory to establish field work intensity would underestimate mechanical workload experienced in the field.     

Perceptual and physiological responses to cycling and running in groups of trained and untrained subjects

An interesting aspect, when comparing athletes, is the effect of specialized training upon both physiological performance and perceptual responses. To study this, four groups (with six individuals each) served as subjects. Two of these consisted of highly specialized individuals (racing cyclists and marathon runners) and the other two of non-specialized individuals (sedentary and all-round trained). Cycling on a cycle ergometer and running on a treadmill were chosen as modes of exercise. Variables measured included heart rate, blood lactate and perceived exertion, rated on two different scales. Results show a linear increase of both heart rate and perceived exertion (rated on the RPE scale) in all four groups, although at different absolute levels. Blood lactate accumulation, during cycling and running, differentiates very clearly between the groups. When heart rate and perceived exertion were plotted against each other, the difference at the same subjective rating (RPE 15) between cycling and running amounted to about 15-20 beats.min-1 in the non-specialized groups. The cyclists exhibited almost no difference at all as compared to 40 beats.min-1 for the runners. It can be concluded that specialized training changes both the physiological as well as the psychological response to exercise.     

Physiological responses and perceived exertion during cycling with superimposed electromyostimulation

The goal of the study was to evaluate and to quantify the effects of local electromyostimulation (EMS) during cycling on the cardiorespiratory system, muscle metabolism, and perceived exertion compared with cycling with no EMS. Ten healthy men (age: 24.6 ± 3.2 years, V[Combining Dot Above]O2max: 54.1 ± 6.0 ml·min·kg) performed 3 incremental cycle ergometer step tests, 1 without and 2 with EMS (30 and 85 Hz) until volitional exhaustion. Lactate values and respiratory exchange ratio were significantly higher at intensities ≥75% peak power output (PPO) when EMS was applied. Bicarbonate concentration, base excess (BE), and Pco2 were significantly lower when EMS was applied compared with the control at intensities ≥75% PPO. Saliva cortisol levels increased because of the exercise but were unaffected by EMS. Furthermore, EMS showed greater effects on CK levels 24 hours postexercise than normal cycling did. Rating of perceived exertion was significantly higher at 100% PPO with EMS. No statistical differences were found for heart rate, pH, and Po2 between the tested cycling modes. The main findings of this study are greater metabolic changes (lactate, respiratory exchange ratio, BE, (Equation is included in full-text article.), Pco2) during cycling with EMS compared with normal cycling independent of frequency, mainly visible at higher work rates. Because metabolic alterations are important for the induction of cellular signaling cascades and adaptations, these results lead to the hypothesis that applied EMS stimulations during cycling exercise might be an enhancing stimulus for skeletal muscle metabolism and related adaptations. Thus, superimposed EMS application during cycling could be beneficial to aerobic performance enhancements in athletes and in patients who cannot perform high workloads. However, the higher demand on skeletal muscles involved must be considered.     

Calcification and associated physiological parameters during a stress event in the scleractinian coral Stylophora pistillata

High calcification rates observed in reef coral organisms are due to the symbiotic relationship established between scleractinian corals and their photosynthetic dinoflagellates, commonly called zooxanthellae. Zooxanthellae are known to enhance calcification in the light, a process referred as "light-enhanced calcification". The disruption of the relationship between corals and their zooxanthellae leads to bleaching. Bleaching is one of the major causes of the present decline of coral reefs related to climate change and anthropogenic activities. In our aquaria, corals experienced a chemical pollution leading to bleaching and ending with the death of corals. During the time course of this bleaching event, we measured multiple parameters and could evidence four major consecutive steps: 1) at month 1 (January 2005), the stress affected primarily the photosystem II machinery of zooxanthellae resulting in an immediate decrease of photosystem II efficiency, 2) at month 2, the stress affected the photosynthetic production of O2 by zooxanthellae and the rate of light calcification, 3) at month 3, there was a decrease in both light and dark calcification rates, the appearance of the first oxidative damage in the zooxanthellae, the disruption of symbiosis, 4) and finally the death of corals at month 6.     

Metabolic, thermoregulatory, and perceptual responses during exercise after lower vs. whole body precooling.

The purpose of this investigation was to compare the thermoregulatory, metabolic, and perceptual effects of lower body (LBI) and whole body (WBI) immersion precooling techniques during submaximal exercise. Eleven healthy men completed two 30-min cycling bouts at 60% of maximal O(2) uptake preceded by immersion to the suprailiac crest (LBI) or clavicle (WBI) in 20 degrees C water. WBI produced significantly lower rectal temperature (T(re)) during minutes 24-30 of immersion and lower T(re), mean skin temperature, and mean body temperature for the first 24, 14, and 16 min of exercise, respectively. Body heat storage rates differed significantly for LBI and WBI during immersion and exercise, although no net differences were observed between conditions. For WBI, metabolic heat production and heart rate were significantly higher during immersion but not during exercise. Thermal sensation was significantly lower (felt colder) and thermal discomfort was significantly higher (less comfortable) for WBI during immersion and exercise. In conclusion, WBI and LBI attenuated T(re) increases during submaximal exercise and produced similar net heat storage over the protocol. LBI minimized metabolic increases and negative perceptual effects associated with WBI.     

Oxidative stress responses during cassava post-harvest physiological deterioration

A major constraint to the development of cassava (Manihot esculenta Crantz) as a crop to both farmers and processors is its starchy storage roots’ rapid post-harvest deterioration, which can render it unpalatable and unmarketable within 24–72 h. An oxidative burst occurs within 15 min of the root being injured, that is followed by the altered regulation of genes, notably for catalase and peroxidase, related to the modulation of reactive oxygen species, and the accumulation of secondary metabolites, some of which show antioxidant properties. The interactions between these enzymes and compounds, in particular peroxidase and the coumarin, scopoletin, are largely confined to the vascular tissues where the visible symptoms of deterioration are observed. These, together with other data, are used to develop a tentative model of some of the principal events involved in the deterioration process.     

Oxidative stress responses during cassava post-harvest physiological deterioration

A major constraint to the development of cassava (Manihot esculenta Crantz) as a crop to both farmers and processors is its starchy storage roots' rapid post-harvest deterioration, which can render it unpalatable and unmarketable within 24–72 h. An oxidative burst occurs within 15 min of the root being injured, that is followed by the altered regulation of genes, notably for catalase and peroxidase, related to the modulation of reactive oxygen species, and the accumulation of secondary metabolites, some of which show antioxidant properties. The interactions between these enzymes and compounds, in particular peroxidase and the coumarin, scopoletin, are largely confined to the vascular tissues where the visible symptoms of deterioration are observed. These, together with other data, are used to develop a tentative model of some of the principal events involved in the deterioration process. Abbreviations: ACMV, African cassava mosaic virus; AFLP, amplified fragment length polymorphism; CAT, catalase; cDNA, complementary deoxyribonucleic acid; CIAT, International Centre for Tropical Agriculture; Cu/ZnSOD, copper/zinc superoxide dismutase; DAB, 3,3-diaminobenzidine tetrahydrochloride; DPPH, 1,1-diphenyl-2-picrylhydrazyl; FeSOD, iron superoxide dismutase; FW, fresh weight; GUS, -glucuronidase; HPTLC, high-performance thin-layer chromatography; HR, hypersensitive response; IEF-PAGE, isoelectric focusing polyacrylamide gel electrophoresis; MAS, marker-assisted selection; MeJa, methyl jasmonate; MnSOD, manganese superoxide dismutase; NADPH, nicotinamide adenine dinucleotide phosphate (reduced form); NBT, nitroblue tetrazolium; PAL, phenylalanine ammonia-lyase; PCD, programmed cell death; PCR, polymerase chain reaction; POX, peroxidase; PPD, post-harvest physiological deterioration; QTL, quantitative trait loci; ROS, reactive oxygen species; RT, room temperature; SAR, systemic acquired resistance; SDS, sodium dodecyl sulfate; SOD, superoxide dismutase     

Physiological responses of beech and sessile oak in a natural mixed stand during a dry summer

Responses of CO2 assimilation and stomatal conductance to decreasing leaf water potential, and to environmental factors, were analysed in a mixed natural stand of sessile oak (Quercus petraea ssp. medwediewii) and beech (Fagus svlvatica L.) in Greece during the exceptionally dry summer of 1998. Seasonal courses of leaf water potential were similar for both species, whereas mean net photosynthesis and stomatal conductance were always higher in sessile oak than in beech. The relationship between net photosynthesis and stomatal conductance was strong for both species. Sessile oak had high rates of photosynthesis even under very low leaf water potentials and high air temperatures, whereas the photosynthetic rate of beech decreased at low water potentials. Diurnal patterns were similar in both species but sessile oak had higher rates of CO2 assimilation than beech. Our results indicate that sessile oak is more tolerant of drought than beech, due, in part, to its maintenance of photosynthesis at low water potential.     

Respiratory responses of elite oarsmen, former oarsmen, and highly trained non-rowers during rowing, cycling and running

The position of the body and use of the respiratory muscles in the act of rowing may limit ventilation and thereby reduce maximal aerobic power relative to that achieved in cycling or running, in spite of the greater muscle mass involved in rowing. This hypothesis was investigated for three groups of male subjects: nine elite senior oarsmen, eight former senior oarsmen and eight highly trained athletes unskilled in rowing. The subjects performed graded exercise to maximal effort on a rowing ergometer, cycle ergometer and treadmill while respiratory minute volume and oxygen consumption were monitored continuously. The VE at a given during intense submaximal exercise (greater than 75% of maximal ) was not significantly lower in rowing compared with that in cycling and treadmill running for any group, which would suggest that submaximal rowing does not restrict ventilation. At maximal effort, and for rowing were less than those for the other types of exercise in all the groups, although the differences were not statistically significant in the elite oarsmen. These data are consistent with a ventilatory limitation to maximal performance in rowing that may have been partly overcome by training in the elite oarsmen. Alternatively, a lower maximal VE in rowing might have been an effect rather than a cause of a lower maximal if maximal was limited by the lower rate of muscle activation in rowing.     

Biomechanical and metabolic responses to seat-tube angle variation during cycling in tri-athletes

One of the most physically demanding parts of triathlon is the transition from cycling to running. Many tri-athletes believe that increasing seat-tube angle (STA) can bring advantages in the following running part. The aim of this study was to evaluate the effects of inverting the support of the seat, for increasing STA, on the metabolic response and on the muscle activation pattern, maintaining a controlled kinematic. Moreover, a muscle-skeletal model was applied to evaluate the hypothesis that increasing STA changes force-producing capabilities of muscles crossing the hip.Ten tri-athletes cycled at two different power levels and with two different STA’s. Gas exchange data, kinematics and surface electromyography (sEMG) were acquired during the tests. sEMG was measured from eight muscles of the right side of the body. A model of muscle mechanics and energy expenditure was applied to estimate variations of force production capabilities and muscle energy consumption between the two STA configurations.Inverting the support of the seat showed no significant effects on kinematic, Oxygen consumption, muscle activations and muscle power production capabilities. Nevertheless, an interesting advantage can be the tendency to less activate gastrocnemius and biceps femoris: this could lead to minor muscle fatigue during the following running phase.     

Internal work and physiological responses during concentric and eccentric cycle ergometry

Internal mechanical work during cycling, required to raise and lower the legs and change their velocities, is shown to be an important factor when interpreting physiological responses to cycle ergometer exercise. The internal work required to move the legs during concentric and eccentric cycle ergometry at different speeds and workloads was calculated from segmental energy changes determined using cinematography and directly using an eccentric ergometer. The mean internal work rates obtained at pedal frequencies of 30, 60 and 90 min-1 were 11.5, 20 and 62 W respectively. When these estimates were added to the external work rates, they increased concentric and decreased eccentric work rates. The largest differences were seen at low work rates and high pedal frequencies during which concentric work rates increased by 51% and eccentric decreased 60% by the inclusion of internal work. When comparisons of concentric and eccentric cycling at equal uncorrected work rates were made, neglecting to include internal work introduced errors ranging from 12 to 97%. The calculated estimates of internal work agreed well with the power supplied by the eccentric ergometer to move the legs passively. The investigations show that the inclusion of internal work is important when comparing physiological responses during concentric and eccentric ergometry, especially when pedal frequencies exceed 60 min-1 and when work rates are small.     

Plasma hormonal and electrolyte alterations in cycling buffaloes (Bubalus bubalis) during hot summer months

Plasma levels of progesterone, prolactin, luteinizing hormone, and electrolytes were monitored by radioimmunoassay in ten cycling buffaloes maintained at Punjab Agricultural University, Ludhiana during the hot summer months of June–July. The plasma progesterone concentration ranged from 0.28±0.04 to 3.09±0.03 ng/ml at various stages of the oestrous cycle. Prolactin values ranged from 319±23 to 371±25 ng/ml and LH levels from 0.95±0.05 to 1.35±0.08 ng/ml. Concentrations differed significantly (P0.05) at various stages of the cycle. Levels of electrolytes, viz. Ca^{+ +}, Na⁺ and K⁺, were well within the normal range. The high levels of prolactin, progesterone and LH during the hot summer were assessed in relation to poor reproductive efficiency in buffaloes.     

Glycerol hyperhydration: physiological responses during cold-air exposure.

Hypohydration occurs during cold-air exposure (CAE) through combined effects of reduced fluid intake and increased fluid losses. Because hypohydration is associated with reduced physical performance, strategies for maintaining hydration during CAE are important. Glycerol ingestion (GI) can induce hyperhydration in hot and temperate environments, resulting in greater fluid retention compared with water (WI) alone, but it is not effective during cold-water immersion. Water immersion induces a greater natriuresis and diuresis than cold exposure; therefore, whether GI might be effective for hyperhydration during CAE remains unknown. This study examined physiological responses, i.e., thermoregulatory, cardiovascular, renal, vascular fluid, and fluid-regulating hormonal responses, to GI in seven men during 4 h CAE (15 degrees C, 30% relative humidity). Subjects completed three separate, double-blind, and counterbalanced trials including WI (37 ml water/l total body water), GI (37 ml water/l total body water plus 1.5 g glycerol/l total body water), and no fluid. Fluids were ingested 30 min before CAE. Thermoregulatory responses to cold were similar during each trial. Urine flow rates were higher (P = 0.0001) with WI (peak 11.8 ml/min, SD 1.9) than GI (5.0 ml/min, SD 1.8), and fluid retention was greater (P = 0.0001) with GI (34%, SD 7) than WI (18%, SD 5) at the end of CAE. Differences in urine flow rate and fluid retention were the result of a greater free water clearance with WI. These data indicate glycerol can be an effective hyperhydrating agent during CAE.