Fatiguing upper body aerobic exercise impairs balance

Douris, PC, Handrakis, JP, Gendy, J, Salama, M, Kwon, D, Brooks, R, Salama, N, and Southard, V. Fatiguing upper body aerobic exercise impairs balance. J Strength Cond Res 25(12): 3299-3305, 2011-There are many studies that have examined the effects of selectively fatiguing lower extremity muscle groups with various protocols, and they have all shown to impair balance. There is limited research regarding the effect of fatiguing upper extremity exercise on balance. Muscle fiber-type recruitment patterns may be responsible for the difference between balance impairments because of fatiguing aerobic and anaerobic exercise. The purpose of our study was to investigate the effect that aerobic vs. anaerobic fatigue, upper vs. lower body fatigue will have on balance, and if so, which combination will affect balance to a greater degree. Fourteen healthy subjects, 7 men and 7 women (mean age 23.5 ± 1.7 years) took part in this study. Their mean body mass index was 23.6 ± 3.2. The study used a repeated-measures design. The effect on balance was documented after the 4 fatiguing conditions: aerobic lower body (ALB), aerobic upper body (AUB), anaerobic lower body, anaerobic upper body (WUB). The aerobic conditions used an incremental protocol performed to fatigue, and the anaerobic used the Wingate protocol. Balance was measured as a single-leg stance stability score using the Biodex Balance System. A stability score for each subject was recorded immediately after each of the 4 conditions. A repeated-measures analysis of variance with the pretest score as a covariate was used to analyze the effects of the 4 fatiguing conditions on balance. There were significant differences between the 4 conditions (p = 0.001). Post hoc analysis revealed that there were significant differences between the AUB, mean score 4.98 ± 1.83, and the WUB, mean score 4.09 ± 1.42 (p = 0.014) and between AUB and ALB mean scores 4.33 ± 1.40 (p = 0.029). Normative data for single-leg stability testing for this age group are 3.9 ± 1.9. Higher scores reflect greater balance deficits. The AUB condition produced the greatest balance deficit. Our data provide evidence of the important role of the upper body in maintaining unilateral standing balance and supports its inclusion as part of rehabilitation and training protocols designed to improve balance.     

运动训练和停训对鲈鲤幼鱼游泳能力的影响

为探讨运动训练和停训对鲈鲤Percocypris pingi幼鱼运动能力的影响,将480尾(体质量为2.18g±0.12g,体长为5.33cm±0.09cm)鲈鲤幼鱼随机分为4组(每组120尾):对照组(C)、无氧训练组(An)、4BL·s^-1组(BL为体长)(H)和2BL·s^-1组(L)(H组和L组每天均训练8h),在15℃±2℃条件下持续训练30d后停训。分别在训练前(T0)、训练30d后(T30)、停训20d后(DT20)和停训50d后(DT50)测定鲈鲤幼鱼的临界游泳速度(Ucrit)和1.5Ucrit条件下的耐受时间。结果显示:(1)持续运动训练显著提高了鲈鲤幼鱼的有氧和无氧运动能力,而力竭运动训练只提高了鲈鲤幼鱼的无氧运动能力;(2)停训20d后,L组的Ucrit显著高于An组和C组,An组、H组和C组间的差异无统计学意义,而An组和H组的耐受时间仍显著高于对照组,L组和C组间的差异无统计学意义;(3)停训50d后,实验组和C组间Ucrit和耐受时间的差异均无统计学意义。因此,运动训练显著提高了鲈鲤幼鱼的有氧和无氧运动能力,但不同训练方式的提升效果及其维持时间不同。     

Cooling different body surfaces during upper and lower body exercise

The effect of varying the body surface area being cooled by a liquid microclimate system was evaluated during exercise heat-stress conditions. Six male subjects performed a total of six exercise (O2 uptake = 1.2 l/min) tests in a hot environment (ambient temperature = 38 degrees C, relative humidity = 30%) while dressed in clothing having low moisture permeability and high insulation. Each subject completed two upper body exercise (U; arm crank) tests: 1) with only the torso surface (T) cooled; and 2) with the surfaces of both the torso and upper arms (TA) cooled [coolant temperature at the inlet (Ti) was 20 degrees C for all upper body tests]. Each subject also completed four lower body exercise (L; walking) tests: 1) with only the T cooled (Ti = 20 degrees C); 2) with only the T cooled (Ti = 26 degrees C); 3) with torso, upper arm, and thigh surface (TAT) cooled (Ti = 20 degrees C); and 4) with TAT cooled (Ti = 26 degrees C). During U exercise, TA cooling had no effects compared with cooling only T. During L exercise, sweat rates, heart rates, and rectal temperature (Tre) changes were less with TAT cooling compared with cooling only the T. Altering Ti had no effect on Tre changes, but higher heart rates were observed with 26 than with 20 degrees C. These data indicate that cooling arms during upper body exercise provides no thermoregulatory advantage, although cooling the thigh surfaces during lower body exercise does provide an advantage.     

Effect of nutritionally enriched coffee consumption on aerobic and anaerobic exercise performance

The purpose of this study was to compare nutritionally enriched JavaFit coffee (JF) to commercially available decaffeinated coffee (P) with regard to impact on endurance and anaerobic power performance in a physically active, college-aged population. Ten subjects (8 men, 2 women) performed two 30-second Wingate anaerobic power tests and 2 cycle ergometer tests (75% VO2 max) to exhaustion. Mean VO2 was measured during each endurance exercise protocol. Excess postexercise oxygen consumption (EPOC) and respiratory exchange ratio (RER) were recorded for 30 minutes following all exercise sessions. Area under the curve analysis was used to compare EPOC between JF and P for all exercise sessions. No differences were seen between JF and P in any of the power performance measures. However, time to exhaustion was significantly (p = 0.05) higher in JF (35.3 +/- 15.2 minutes) compared with P (27.3 +/- 10.7 minutes). No difference between JF and P were seen in EPOC in either the aerobic or anaerobic exercise sessions. A significant (p < 0.05) difference in average 30-minute postanaerobic power exercise RER was seen between JF (0.87 +/- 0.04) and P (0.83 +/- 0.03), but not following endurance exercise. A nutritionally-enriched coffee beverage appears to enhance time to exhaustion during aerobic exercise, but does not provide an ergogenic benefit during anaerobic exercise.     

Time estimation performance before, during, and following physical activity

An experiment is reported which evaluated performance on a 10-sec unfilled time interval estimation task before, during, and after physical work on a cycle ergometer at relative intensities of 30 and 60% VO2max. Results from eleven healthy male subjects revealed a significant increase in time estimation variability and a decrease in the mean estimated time intervals during exercise compared to non-exercise phases. These findings are part of a growing body of evidence which indicates that exercise and its severity has a substantive impact on perceptual and cognitive performance, particularly the ability to synchronize and anticipate the timing of events.     

Heat extraction through the palm of one hand improves aerobic exercise endurance in a hot environment.

In situations where the accumulation of internal heat limits physical performance, enhanced heat extraction from the body should improve performance capacity. The combined application of local subatmospheric pressure (35-45 mmHg) to an entire hand (to increase blood volume) and a heat sink (18-22 degrees C) to the palmar surface were used to draw heat out of the circulating blood. Subjects walked uphill (5.63 km/h) on a treadmill in a 40 degree C environment. Slopes of the treadmill were held constant during paired experimental trials (with and without the device). Heat extraction attenuated the rate of esophageal temperature rise during exercise (2.1 +/- 0.4 degrees and 2.9 +/- 0.5 degrees C/h, mean +/- SE, with and without the device, respectively; n = 8) and increased exercise duration (46.1 +/- 3.4 and 32.3 +/- 1.7 min with and without the device, respectively; n = 18). Hand cooling alone had little effect on exercise duration (34.1 +/- 3.0, 38.0 +/- 3.5, and 57.0 +/- 6.4 min, for control, cooling only, and cooling, and subatmospheric pressure, respectively; n = 6). In a longer term study, nine subjects participated in two or four trials per week for 8 wk. The individual workloads (treadmill slope) were varied weekly. Use of the device had a beneficial effect on exercise endurance at all workloads, but the benefit proportionally decreased at higher workloads. It is concluded that heat can be efficiently removed from the body by using the described technology and that such treatment can provide a substantial performance benefit in thermally stressful conditions.     

Physiological determinants of the candidate physical ability test in firefighters

The purpose of this study was to examine the relative importance of physiological characteristics during firefighting performance, as assessed by the Candidate Physical Ability Test (CPAT). Subjects included career and volunteer firefighters aged 18-39 (N = 33). Upper- and lower-body strength, muscle endurance, lower body muscle power, body composition analysis, aerobic capacity, anaerobic fitness, and the heart rate (HR) and blood pressure response to stair climbing were assessed to determine the physiological characteristics of the subjects. To quantify firefighting performance, the CPAT was administered by members of the fire service. Absolute and relative mean power during the Wingate anaerobic cycling test (WAnT), relative peak power during the WAnT, and absolute maximal oxygen uptake (VO2max) were significantly higher in those who passed the CPAT (N = 18), compared to those who failed (N = 15; p < 0.01). Mean power during the WAnT, fatigue index during WAnT, absolute VO2max, upper body strength, grip strength, and the HR response to stair climbing were significantly related to CPAT performance time (p < 0.01). Absolute VO2max and anaerobic fatigue resistance during WAnT best predicted CPAT performance (Adj. R2 = 0.817; p < 0.001). Performance on the ceiling breach and pull was the only CPAT task that was not significantly related to the physiological characteristics assessed. Measures of anaerobic and cardiovascular fitness best predict overall CPAT performance, and individual task performance. Remedial programs aimed at improving firefighting performance should target anaerobic and aerobic fitness qualities.     

The impact of electronic mail versus print delivery of an exercise program on muscular strength and aerobic capacity in people with type 2 diabetes

Previous research indicates that the Internet, electronic mail (e-mail), and printed materials can be used to deliver interventions to improve physical activity in people with type 2 diabetes. However, no studies have been conducted investigating the effect of e-mail or print delivery of an exercise program on muscular strength and aerobic capacity in people with type 2 diabetes. The purpose of this clinical trial was to investigate the impact of e-mail vs. print delivery of an exercise program on muscular strength and aerobic capacity in people with type 2 diabetes. Nineteen participants with type 2 diabetes were allocated to either a group that was delivered a prescribed exercise program using e-mail (e-mail group, n = 10) or a group that was delivered the same prescribed exercise program in print form (print group, n = 9). Chest press and leg press estimated one-repetition maximum (1-RM) scores as well as estimated peak oxygen uptake ([latin capital V with dot above]O2peak) were measured at baseline and follow-up. Intention-to-treat analysis indicated significant improvements in chest press (mean = 7.00 kg, p = 0.001, effect size = 2.22) and leg press (mean = 19.32 kg, p = 0.002, effect size = 1.98) 1-RM scores and [latin capital V with dot above]O2peak (mean = 9.38 mL of oxygen uptake per kilogram of body mass per minute, p = 0.01, effect size = 1.45) within the e-mail group. Within the print group, significant improvements in chest press (mean = 9.13 kg, p = 0.01, effect size = 1.49) and leg press (mean = 16.68 kg, p = 0.01, effect size = 1.31) 1-RM scores and [latin capital V with dot above]O2peak (mean = 5.14 ml of oxygen uptake per kilogram of body mass per minute, p = 0.03, effect size = 1.14) were found. No significant between-group differences in improvements were found. Clinicians can deliver a prescribed exercise program, either by e-mail or in print form, to significantly improve muscular strength and aerobic capacity in people with type 2 diabetes, and expect similar outcomes.     

HIGH-INTENSITY EXERCISE TRAINING INDUCES MORPHOLOGICAL AND BIOCHEMICAL CHANGES IN SKELETAL MUSCLES

In the present study we investigated the effect of two different exercise protocols on fibre composition and metabolism of two specific muscles of mice: the quadriceps and the gastrocnemius. Mice were run daily on a motorized treadmill, at a velocity corresponding to 60% or 90% of the maximal running velocity. Blood lactate and body weight were measured during exercise training. We found that at the end of training the body weight significantly increased in high-intensity exercise mice compared to the control group (P=0.0268), whereas it decreased in low-intensity exercise mice compared to controls (P=0.30). In contrast, the food intake was greater in both trained mice compared to controls (P < 0.0001 and P < 0.0001 for low-intensity and high-intensity exercise mice, respectively). These effects were accompanied by a progressive reduction in blood lactate levels at the end of training in both the exercised mice compared with controls (P=0.03 and P < 0.0001 for low-intensity and high-intensity exercise mice, respectively); in particular, blood lactate levels after high-intensity exercise were significantly lower than those measured in low-intensity exercise mice (P=0.0044). Immunoblotting analysis demonstrated that high-intensity exercise training produced a significant increase in the expression of mitochondrial enzymes contained within gastrocnemius and quadriceps muscles. These changes were associated with an increase in the amount of slow fibres in both these muscles of high-intensity exercise mice, as revealed by the counts of slow fibres stained with specific antibodies (P < 0.0001 for the gastrocnemius; P=0.0002 for the quadriceps). Our results demonstrate that high-intensity exercise, in addition to metabolic changes consisting of a decrease in blood lactate and body weight, induces an increase in the mitochondrial enzymes and slow fibres in different skeletal muscles of mice, which indicates an exercise-induced increase in the aerobic metabolism.     

Does aerobic and strength exercise sequence in the same session affect the oxygen uptake during and postexercise?

Concurrent training is a strategy employed in both general fitness and sports conditioning. The purpose of this study was to compare the responses of VO2 in different combinations of strength exercise with aerobic interval exercise. Eight men (23.6 ± 4.2 years, 178 ± 6.3 cm, 77 ± 7.9 kg, 7.67 ± 1.95% body fat) completed 3 combinations of strength training (ST) and aerobic training (AT) in a randomized order with a 7-day recovery period: AT before ST exercises, AT between 2 blocks of ST exercises, and AT after ST exercises. The ST comprised 4 exercises performed in 3 sets of 10 reps and 2 exercises, abdominal crunch and lumbar extension, performed in 3 sets of 30 and 20 reps, respectively. The AT consisted of a 20-minute interval cycling. There were no significant differences in the values of absolute or relative VO2, in the heart rate (HR) and in the respiratory exchange ratio (RER) when the 3 sessions (during + postexercise measurements) were compared (values are mean ± SD). Analyzing only ST in each session, differences were detected in the RER values (F = 4.714; p < 0.05; η2 = 0.308) between AT before ST and AT in the middle of ST (1.01 ± 0.97 vs. 1.11 ± 0.07, respectively). In all sequences, there was a significant increase (p < 0.05) in the values of relative and absolute VO2 and HR, and a significant decrease in RER values (p < 0.05) from the first to the second part of the ST session. The values of absolute or relative VO2, HR, and RER did not vary significantly among the 3 sessions as compared with the AT after ST. These data support the hypothesis that ST and AT, when performed in sequence in the same session, do not seem to affect the overall oxygen consumption during the exercise session. Therefore, training sessions may incorporate both modalities without apparent impact on aerobic exercise.     

Aerobic parameters of exercise as a function of body size during growth in children

To examine the relationship between body weight in children and aerobic parameters of exercise, we determined the anaerobic threshold (AT), maximum O2 uptake (VO2max), work efficiency, and response time for O2 uptake (RT-VO2) in 109 healthy children (51 girls and 58 boys, range 6-17 yr old) using a cross-sectional study design. Gas exchange during exercise was measured breath by breath. The protocol consisted of cycle ergometry and a linearly increasing work rate (ramp) to the limit of the subject's tolerance. Both AT and VO2max increased systematically with body weight, whereas work efficiency and RT-VO2 were virtually independent of body size. The ratio of AT to VO2max decreased slightly with age, and its mean value was 60%. AT scaled to body weight to the power of 0.92, not significantly different from the power of 1.01 for VO2max. Thus both the AT and the VO2max increase in a highly ordered manner with increasing size, and as judged by AT/VO2max, the onset of anaerobic metabolism during exercise occurred at a relatively constant proportion of the overall limit of the gas transport system. We conclude that in children cardiorespiratory responses to exercise are regulated at optimized values despite overall change in body size during growth.     

Passive Leg Raising Correlates with Future Exercise Capacity after Coronary Revascularization

Hemodynamic properties affected by the passive leg raise test (PLRT) reflect cardiac pumping efficiency. In the present study, we aimed to further explore whether PLRT predicts exercise intolerance/capacity following coronary revascularization. Following coronary bypass/percutaneous coronary intervention, 120 inpatients underwent a PLRT and a cardiopulmonary exercise test (CPET) 2–12 days during post-surgery hospitalization and 3–5 weeks after hospital discharge. The PLRT included head-up, leg raise, and supine rest postures. The end point of the first CPET during admission was the supra-ventilatory anaerobic threshold, whereas that during the second CPET in the outpatient stage was maximal performance. Bio-reactance-based non-invasive cardiac output monitoring was employed during PLRT to measure real-time stroke volume and cardiac output. A correlation matrix showed that stroke volume during leg raise (SV_LR) during the first PLRT was positively correlated (R = 0.653) with the anaerobic threshold during the first CPET. When exercise intolerance was defined as an anaerobic threshold < 3 metabolic equivalents, SV_LR / body weight had an area under curve value of 0.822, with sensitivity of 0.954, specificity of 0.593, and cut-off value of 1504·10^-3mL/kg (positive predictive value 0.72; negative predictive value 0.92). Additionally, cardiac output during leg raise (CO_LR) during the first PLRT was related to peak oxygen consumption during the second CPET (R = 0.678). When poor aerobic fitness was defined as peak oxygen consumption < 5 metabolic equivalents, CO_LR / body weight had an area under curve value of 0.814, with sensitivity of 0.781, specificity of 0.773, and a cut-off value of 68.3 mL/min/kg (positive predictive value 0.83; negative predictive value 0.71). Therefore, we conclude that PLRT during hospitalization has a good screening and predictive power for exercise intolerance/capacity in inpatients and early outpatients following coronary revascularization, which has clinical significance.     

Metabolic and ventilatory responses to steady state exercise relative to lactate thresholds

The metabolic and ventilatory responses to steady state submaximal exercise on the cycle ergometer were compared at four intensities in 8 healthy subjects. The trials were performed so that, after a 10 min adaptation period, power output was adjusted to maintain steady state VO2 for 30 min at values equivalent to: (1) the aerobic threshold (AeT); (2) between the aerobic and the anaerobic threshold (AeTAnT); (3) the anaerobic threshold (AnT); and (4) between the anaerobic threshold and VO2max (AnTmax). Blood lactate concentration and ventilatory equivalents for O2 and CO2 demonstrated steady state values during the last 20 min of exercise at the AeT, AeAnT and AnT intensities, but increased progressively until fatigue in the AnTmax trial (mean time = 16 min). Serum glycerol levels were significantly higher at 40 min of exercise on the AeAnT and the AnT when compared to AeT, while the respiratory exchange ratios were not significantly different from each other. Thus, metabolic and ventilatory steady state can be maintained during prolonged exercise at intensities up to and including the AnT, and fat continues to be a major fuel source when exercise intensities are increased from the AeT to the AnT in steady state conditions. The blood lactate response to exercise suggests that, for the organism as a whole, anaerobic glycolysis plays a minor role in the energy release system at exercise intensities upt to and including the AnT during steady state conditions.     

The effects of 10 weeks of resistance training combined with β-alanine supplementation on whole body strength, force production, muscular endurance and body composition

Carnosine (Carn) occurs in high concentrations in skeletal muscle is a potent physico-chemical buffer of H⁺ over the physiological range. Recent research has demonstrated that 6.4 g.day⁻¹ of β-alanine (β-ala) can significantly increase skeletal muscle Carn concentrations (M-[Carn]) whilst the resultant change in buffering capacity has been shown to be paralleled by significant improvements in anaerobic and aerobic measures of exercise performance. Muscle carnosine increase has also been linked to increased work done during resistance training. Prior research has suggested that strength training may also increase M-[Carn] although this is disputed by other studies. The aim of this investigation is to assess the effect of 10 weeks resistance training on M-[Carn], and, secondly, to investigate if increased M-[Carn] brought about through β-ala supplementation had a positive effect on training responses. Twenty-six Vietnamese sports science students completed the study. The subjects completed a 10-week resistance-training program whilst consuming 6.4 g.day⁻¹ of β-ala (β-ALG) or a matched dose of a placebo (PLG). Subjects were assessed prior to and after training for whole body strength, isokinetic force production, muscular endurance, body composition. β-Alanine supplemented subjects increased M-[Carn] by 12.81 ± 7.97 mmol.kg⁻¹ dry muscle whilst there was no change in PLG subjects. There was no significant effect of β-ala supplementation on any of the exercise parameters measured, mass or % body fat. In conclusion, 10 weeks of resistance training alone did not change M-[Carn].     

Measurement of maximum oxygen consumption in Guinea fowl Numida meleagris indicates that birds and mammals display a similar diversity of aerobic scopes during running

Judgement of exercise performance in birds has been hampered by a paucity of data on maximal aerobic capacity. We measured the maximal rate of oxygen consumption (Vo2,max) in running guinea fowl Numida meleagris, a bird that has been used in several previous studies of avian running. Mean Vo2,max during level treadmill running was 97.5+/-3.7 mL O(2) kg(-1) min(-1) (mean+/-SEM, N=5). Vo2,max was on average 6% higher when the birds ran uphill compared with the value during level running (paired t-test, P=0.041, N=5). The mean basal rate of oxygen consumption (Vo2,bmr) of the same individuals was 7.9+/-0.5 mL O(2) kg(-1) min(-1). Mean factorial aerobic scope based on individually measured values of Vo2,max and Vo2,bmr was 13.2+/-0.6 (mean+/-SEM, N=5). This value was considerably lower than the factorial aerobic scope previously measured during running in Rhea americana, a large flightless ratite. The difference in factorial scope between these two running birds likely reflects the effects of body size as well as size-independent differences in the ability to deliver and use oxygen. These data confirm a previous prediction that birds have a diversity of factorial aerobic scopes similar to that exhibited by mammals.     

Oxygen Demand and Energy Cost of Intense Muscular Activity in Humans

Changes in the kinetics of aerobic and anaerobic metabolism were studied in 26 highly profiled athletes performing bicycle ergometer exercise. The different intensity exercise sessions included those with a critical intensity corresponding to the maximum oxygen consumption up to value of the maximum anaerobic intensity of about 10 MMR units. The maximal aerobic metabolism was maintained in the exercises with a relative intensity of 1.0 to 2.5 MMR units. At the higher values of the exercise relative intensity, the oxygen current consumption exponentially decreased. An increase in the rate of anaerobic glycolytic energy production, which was first recorded at the threshold of anaerobic metabolism (W _AT = 0.5 MMR units), increased linearly with a further increase in the exercise relative intensity up to the level of the exhaustion intensity (W _ex = 4.7 MMR units). A sharp increase in the rate of an alactic anaerobic process was found at the relative intensity values of 2.5 MMR units, and this increase grew linearly up to values of the maximal anaerobic intensity (W _max = 9.5 MMR units).     

Active dehydration impairs upper and lower body anaerobic muscular power

We examined the effects of active dehydration by exercise in a hot, humid environment on anaerobic muscular power using a test-retest (euhydrated and dehydrated) design. Seven subjects (age, 27.1 +/- 4.6 years; mass, 86.4 +/- 9.5 kg) performed upper and lower body Wingate anaerobic tests prior to and after a 1.5-hour recovery from a heat stress trial of treadmill exercise in a hot, humid environment (33.1 +/- 3.1C = 55.1 +/- 8.9% relative humidity) until a 3.1 +/- 0.3% body mass loss was achieved. Dehydration was confirmed by a significant body mass loss (P < 0.001), urine color increase (P = 0.004), and urine specific gravity increase (P = 0.041). Motivation ratings were not significantly different (P = 0.059), and fatigue severity was significantly (P = 0.009) increased 70% in the dehydrated compared to the euhydrated condition. Compared to the euhydrated condition, the dehydrated condition mean power was significantly (P = 0.014) decreased 7.17% in the upper body and 19.20% in the lower body. Compared to the euhydrated condition, the dehydrated condition peak power was significantly (P = 0.013) decreased 14.48% in the upper body and 18.36% in the lower body. No significant differences between the euhydrated and dehydrated conditions were found for decrease in power output (P = 0.219, power = 0.213). Our findings suggest that dehydration of 2.9% body mass decreases the ability to generate upper and lower body anaerobic power. Coaches and athletes must understand that sports performance requiring anaerobic strength and power can be impaired by inadequate hydration and may contribute to increased susceptibility to musculoskeletal injury.     

Metformin inhibits mitochondrial adaptations to aerobic exercise training in older adults

Metformin and exercise independently improve insulin sensitivity and decrease the risk of diabetes. Metformin was also recently proposed as a potential therapy to slow aging. However, recent evidence indicates that adding metformin to exercise antagonizes the exercise‐induced improvement in insulin sensitivity and cardiorespiratory fitness. The purpose of this study was to test the hypothesis that metformin diminishes the improvement in insulin sensitivity and cardiorespiratory fitness after aerobic exercise training (AET) by inhibiting skeletal muscle mitochondrial respiration and protein synthesis in older adults (62 ± 1 years). In a double‐blinded fashion, participants were randomized to placebo (n = 26) or metformin (n = 27) treatment during 12 weeks of AET. Independent of treatment, AET decreased fat mass, HbA1c, fasting plasma insulin, 24‐hr ambulant mean glucose, and glycemic variability. However, metformin attenuated the increase in whole‐body insulin sensitivity and VO₂max after AET. In the metformin group, there was no overall change in whole‐body insulin sensitivity after AET due to positive and negative responders. Metformin also abrogated the exercise‐mediated increase in skeletal muscle mitochondrial respiration. The change in whole‐body insulin sensitivity was correlated to the change in mitochondrial respiration. Mitochondrial protein synthesis rates assessed during AET were not different between treatments. The influence of metformin on AET‐induced improvements in physiological function was highly variable and associated with the effect of metformin on the mitochondria. These data suggest that prior to prescribing metformin to slow aging, additional studies are needed to understand the mechanisms that elicit positive and negative responses to metformin with and without exercise.     

Serum vanadium concentrations in different sports modalities

AimsThe aim of this study was to compare serum vanadium (V) concentrations between athletes of different sports modalities and people who did not practise physical exercise regularly.MethodsOne hundred and twenty-one subjects divided into a control group (CG; n = 37; 1.75 ± 0.03 m; 79.45 ± 10.20 kg; 24.72 ± 6.06 years) and an athletes’ group (AG; n = 84; 1.77 ± 0.05 m; 66.34 ± 6.12 kg; 19.57 ± 1.95 years) participated in this research. AG were classified by sports modality: aerobic (AE; n = 26), anaerobic (ANA; n = 22); aerobic-anaerobic (AE-ANA; n = 36). Serum V concentrations were analysed by inductively coupled plasma mass spectrometry.ResultsAG showed higher V concentrations compared to CG (p < 0.01). AE obtained higher concentrations compared to ANA and AE-ANA (p < 0.05).ConclusionsPhysical training could increase serum V levels. Specifically, aerobic sports modalities could increase serum V levels to a greater extent than other sports modalities.     

Practical application of fundamental concepts in exercise physiology

The collection of primary data in laboratory classes enhances undergraduate practical and critical thinking skills. The present article describes the use of a lecture program, running in parallel with a series of linked practical classes, that emphasizes classical or standard concepts in exercise physiology. The academic and practical program ran under the title of a particular year II module named Sports Performance: Physiology and Assessment, and results are presented over a 3-yr period (2004-2006), based on an undergraduate population of 31 men and 34 women. The module compared laboratory-based indexes of endurance (e.g., ventilatory threshold and exercise economy) and high-intensity exercise (e.g., anaerobic power), respectively, with measures of human performance (based on 20-m shuttle run tests). The specific experimental protocols reinforced the lecture content to improve student understanding of the physiological and metabolic responses (and later adaptations) to exercise. In the present study, the strongest relationship with endurance performance was the treadmill velocity at maximal aerobic power (r = +0.88, P < 0.01, n = 51); in contrast, the strongest relationship with high-intensity exercise performance was the mean power output (in W/kg) measured during a 30-s all-out cycle ergometer sprint (r = +0.80, P < 0.01, n = 48). In class student data analysis improved undergraduate indepth or critical thinking during seminars and enhanced computer and data presentation skills. The endurance-based laboratories are particularly useful for examining the underlying scientific principles that determine aerobic performance but could equally well be adapted to investigate other topics, e.g., differences in the exercise response between men and women.