30-s Exercise Research Articles

English

Introduction: Lung diffusion capacity of carbon monoxide (DLCO) provides a measure of gas transfer in the lungs, which increase in relation to exercise and decrease in the presence of lung interstitial disease. The aim of this study is to evaluate the changes in lung diffusion after anaerobic and aerobic exercise in a cycle ergometer. Material and method: The participants were 9 healthy active subjects, including six females and three males (age: 24.3 ± 3.1 years). Lung diffusion capacity for carbon monoxide (DLCO) was studied under two different protocols: In the first day, DLCO was measured at SL at rest (SL-R), after 30-s maximal exercise (SL-ANA), and after 15-min moderate continuous exercise (SL-AER). In the second day, DLCO was evaluated at rest at SL, and then at HA (4,000 m) at rest (HA-R) and after 30-min of moderate interval exercise (HA-AER). Results: There was an increase in DLCO from rest to after SL-ANA (32.5 ± 6.4 to 40.3 ± 11.6 mL·min-1·mmHg-1, P = 0.027). In the second day, DLCO was evaluated at rest at SL, and then at HA (4,000 m) at rest (HA-R) and after 30-min of moderate interval exercise (HA-AER). During HA exposure, there was no changes in DLCO, either at HA-R, or after HA-AER. Conclusions: Lung diffusion capacity largely increased after 30-s maximal exercise in a cycle ergometer, although the O2 -dependence is small during this type of anaerobic exercise. Thus, exercise intensity may be a key modulator of the changes in lung diffusing capacity in relation to exercise.

Rapid adjustments to autonomic control of cardiac rhythm at the onset of isometric exercise in healthy young adults.

Sympathetic nervous system (SNS) and parasympathetic nervous system (PNS) influences on cardiac rhythm at the onset of exercise, a time of rapid autonomic adjustments, are clinically important areas of investigation. Continuous wavelet transform (CWT) involves time-frequency-based heart rate variability (HRV) analysis allowing investigation of autonomic influences on cardiac rhythm during short durations of exercise. Therefore, the purpose of this study was to characterize SNS and PNS influences on cardiac rhythm at the onset of isometric exercise in healthy young adults. CWT analysis was retrospectively applied to R-R interval data (electrocardiogram) previously collected from 14 healthy young adults (26 ± 2 years) who performed 30-s, one-legged, isometric, calf exercise at 70% maximal voluntary contraction (MVC; 70% MVC trial) or rested (0% MVC trial). Absolute and normalized low-frequency (aLF, nLF; 0.04-0.15 Hz) and high-frequency (aHF, nHF; 0.15-0.4Hz) bands and LF/HF were used to analyze one 30-s baseline period and six 5-s time windows during the 30-s exercise (70% MVC) or rest (0% MVC). Statistical analysis involved two-way analysis of variance with post-hoc analysis. aHF, aLF, LF/HF, nHF, and nLF displayed a trial-time interaction (all p ≤ 0.027). In the 70% compared to the 0% MVC trial, aHF and nHF were lower after 5-30 s (all p ≤ 0.040), aLF was lower after 20-30 s (all p ≤ 0.011) and LF/HF and nLF were higher after 5-20 s (all p ≤ 0.045). These results indicate the reduction of the PNS influence on cardiac rhythm begins sooner than the augmentation of the SNS influence at the onset of isometric exercise in healthy young adults.

Changes in energy system contributions to the Wingate anaerobic test in climbers after a high altitude expedition.

The Wingate anaerobic test measures the maximum anaerobic capacity of the lower limbs. The energy sources of Wingate test are dominated by anaerobic metabolism (~ 80%). Chronic high altitude exposure induces adaptations on skeletal muscle function and metabolism. Therefore, the study aim was to investigate possible changes in the energy system contribution to Wingate test before and after a high-altitude sojourn. Seven male climbers performed a Wingate test before and after a 43-day expedition in the Himalaya (23days above 5.000m). Mechanical parameters included: peak power (PP), average power (AP), minimum power (MP) and fatigue index (FI). The metabolic equivalents were calculated as aerobic contribution from O2 uptake during the 30-s exercise phase (WVO2), lactic and alactic anaerobic energy sources were determined from net lactate production (WLa) and the fast component of the kinetics of post-exercise oxygen uptake (WPCr), respectively. The total metabolic work (WTOT) was calculated as the sum of the three energy sources. PP and AP decreased from 7.3 ± 1.1 to 6.7 ± 1.1W/kg and from 5.9 ± 0.7 to 5.4 ± 0.8W/kg, respectively, while FI was unchanged. WTOT declined from 103.9 ± 28.7 to 83.8 ± 17.8kJ. Relative aerobic contribution remained unchanged (19.9 ± 4.8% vs 18.3 ± 2.3%), while anaerobic lactic and alactic contributions decreased from 48.3 ± 11.7 to 43.1 ± 8.9% and increased from 31.8 ± 14.5 to 38.6 ± 7.4%, respectively. Chronic high altitude exposure induced a reduction in both mechanical and metabolic parameters of Wingate test. The anaerobic alactic relative contribution increased while the anaerobic lactic decreased, leaving unaffected the overall relative anaerobic contribution to Wingate test.

Comparable Blood Velocity Changes in Middle and Posterior Cerebral Arteries During and Following Acute High‐Intensity Exercise in Young Fit Women

The influence of high‐intensity exercise training (HIIT) on cerebral blood flow (CBF) regulation remains unclear. HIIT induces surges in mean arterial pressure (MAP), which could be transmitted to the brain, especially early after exercise onset. The aims of this study were to 1) describe regional CBF changes during and following 30 s of high‐intensity exercise and; 2) examine whether dynamic cerebral autoregulation (dCA) is associated with CBF changes. Ten women (age: 26 ± 6 yrs; VO2max: 48.6 ± 3.8 ml×kg×min−1) cycled for 30 s at the workload reached at VO2max followed by 3 min of passive recovery. dCA was characterized using transfer function analysis of forced oscillations induced by repeated squat‐stands (0.05 and 0.10 Hz). Middle (MCAvmean) and posterior cerebral artery mean blood velocities (PCAvmean; transcranial Doppler), MAP (finger photoplethysmography) and end‐tidal carbon dioxide partial pressure (PETCO2; gaz analyzer) were measured. MCAvmean (+19 ± 10%) and PCAvmean (+21 ± 14%) increased early after exercise onset, returning toward baseline values afterwards. MAP increased throughout exercise (p<0.0001). PETCO2 initially decreased by 3 ±2 mmHg (p<0.0001) before returning to baseline values at end‐exercise. During recovery, MCAvmean (+43 ±15%), PCAvmean (+42 ± 15%) and PETCO2 (+11 ± 3 mmHg; p<0.0001) increased. TFA gain was higher in the MCA (p < 0.0001). Other dCA metrics were comparable between arteries and unrelated to exercise‐induced cerebral blood velocity changes. In young fit women, blood velocity changes during and following a 30‐s high‐intensity exercise are comparable between MCA and PCA and unrelated to dCA.Support or Funding InformationL.L. and S.I. are supported by a doctoral training scholarship from the Fonds de recherche du Québec – Santé (FRQS).

Is the cross-over effect of a unilateral high-intensity leg extension influenced by the sex of the participants?

BackgroundWhile performing a unilateral muscle contraction, electrical muscle activity also arises in the contralateral homologous muscle, muscle group, or limb. When the muscle contraction induces muscle fatigue, females show not only a greater resistance than males but also a reduced contralateral muscle activation. The study aimed at investigating whether, during a high-intensity 30-s unilateral maximal effort isometric leg extension exercise, the contralateral non-exercising limb (NEL) knee extensor muscle activation would differ between females and males.MethodsTwenty participants, 11 females (23.80 ± 2.15 years old) and 9 males (26.50 ± 2.45 years old), performed a unilateral 30-s exercise while surface electromyography (sEMG) was measured from the vastus lateralis (VL), vastus medialis (VM), and rectus femoris (RF) on both limbs. The maximal voluntary contraction (MVC) was measured for both the exercising limb (EL) and the NEL before (MVC PRE) and after (MVC POST) the 30-s exercise to assess muscle fatigue.ResultsWhile both females and males exhibited muscle fatigue in the EL (p = 0.015), females exhibited a lower MVC reduction than males (p = 0.042), suggesting that females were less fatigued than males. Although no muscle fatigue, i.e., no MVC force reduction was found in the NEL for either group before and after the 30-s exercise, the muscle activity of the VL was found to be of greater magnitude during the MVC POST only for females (p = 0.047) while it remained unchanged for males. During the 30-s exercise, the force output of the EL decreased only for males (p = 0.029) while females showed a preservation of the force output (p > 0.05). The sEMG activity of the NEL during the 30-s unilateral exercise increased for both groups in all measured muscles (all p-values < 0.03).ConclusionsLikely, different underlying muscle fatigue mechanisms occurred in the EL between females and males. Yet, our findings suggest that the cross-over effect to the NEL during the 30-s exercise occurred in a similar fashion in both groups. The current study suggests that the contralateral muscle activation seen with a unilateral exercise is independent of the sex of individuals. Therefore, unilateral training or rehabilitation-based protocols would similarly impact females and males.

The 1,500-m Rowing Performance is Highly Dependent on Modified Wingate Anaerobic Test Performance in National-Level Adolescent Rowers.

The aim of the current study was to determine whether the anaerobic performance assessed by a modified Wingate test could account for the 1,500-m rowing ergometer performance in young competitive rowers. Fourteen national-level adolescent rowers performed on a rowing ergometer i) a 30-s allout exercise (i.e., modified Wingate test) and ii) a 1,500-m all-out exercise (i.e., rowing performance). For each of these two exercises, the mean power output was considered as the main performance criterion (PWIN and P1500, respectively). PWIN was correlated to P1500 (r2 = .83, p < .0001, β = 100%). Furthermore, the estimated total muscle mass was correlated to PWIN and P1500 (r2 = .72 and r2 = .83, p < .0001, β = 100%, respectively). The allometric scaling also indicated that total muscle mass accounts 62% for the relationship between PWIN and P1500. Our results highlight the importance of considering the contribution of total muscle mass and anaerobic energy pathways to 1,500-m rowing performance in competitive adolescent rowers. Therefore, the modified Wingate test could be used by rowing coaches to potentially identify talented young rowers.

Increased oxygenation of the cerebral prefrontal cortex prior to the onset of voluntary exercise in humans.

To determine whether output from the forebrain (termed central command) may descend early enough to increase cardiac and renal sympathetic outflows at the onset of voluntary exercise, we examined the changes in regional tissue blood flows of bilateral prefrontal cortices with near-infrared spectroscopy, precisely identifying the onset of voluntary ergometer 30-s exercise at 41 ± 2% of the maximal exercise intensity in humans. Prefrontal oxygenated-hemoglobin (Oxy-Hb) concentration was measured as index of regional blood flow unless deoxygenated-hemoglobin concentration remained unchanged. Prefrontal Oxy-Hb concentration increased significantly (P < 0.05) 5 s prior to the onset of exercise with arbitrary start, whereas such increase in prefrontal Oxy-Hb was absent before exercise abruptly started by a verbal cue. Furthermore, the increase in prefrontal Oxy-Hb observed at the initial 15-s period of exercise was greater with arbitrary start than cued start. The prefrontal Oxy-Hb, thereafter, decreased during the later period of exercise, irrespective of either arbitrary or cued start. The reduction in prefrontal Oxy-Hb had the same time course and response magnitude as that during motor-driven passive exercise. Cardiac output increased at the initial period of exercise, whereas arterial blood pressure and total peripheral resistance decreased. The depressor response was more pronounced (P < 0.05) with arbitrary start than cued start. Taken together, it is suggested that the increase in prefrontal Oxy-Hb observed prior to the onset of voluntary exercise may be in association with central command, while the later decrease in the Oxy-Hb during exercise may be in association with feedback stimulated by mechanical limb motion.

One‐minute exercise is best for evaluation of postexercise exhaustion in myasthenia gravis

To find the best exercise duration for postexercise exhaustion by decrement (PEE-D) in myasthenia gravis (MG). In 32 tests in 32 MG patients, repetitive nerve stimulation was performed in the abductor digiti quinti muscle. The 3 Hz responses for 2 s were obtained with supramaximal stimulation at rest, and immediately after (PE0), 30 s after (PE30s), and 1, 2, 3, and 4 min after 10-s, 30-s, and 1-min exercises. Compared with the decrement at rest, a significantly greater decrement was found at PE2m and PE3m after 30-s exercise, and at PE2m, PE3m, and PE4m after 1-min exercise. In 11 patients who showed a decremental response only with exercise, PEE-D was observed in 5 after 30-s exercise and in 8 after 1-min exercise. One-minute exercise is best for evaluation of PEE-D in MG.

Interval training attenuates the metabolic disturbances in type 1 diabetes rat model

This study investigated the effect of interval training on blood biochemistry and immune parameters in type 1 diabetic rats. Male Wistar rats were divided into four groups: sedentary (SE, n = 15), interval training (IT, n = 17), diabetic sedentary (DSE, n = 17), diabetic interval training (DIT, n = 17). Diabetes was induced by i.v. injection of streptozotocin (60 mg/kg). Swimming Interval Training consisted of 30-s exercise with 30-s rest, for 30 minutes, during 6 weeks, four times a week, with an overload of 15% of body mass. Plasma glucose, lactate, triacylglycerol and total cholesterol concentrations, phagocytic capacity, cationic vesicle content, and superoxide anion and hydrogen peroxide production by blood neutrophils and peritoneal macrophages were evaluated. Proliferation of mesenteric lymphocytes was also estimated. Interval training resulted in attenuation of the resting hyperglycemic state and decreased blood lipids in the DIT group. Diabetes increased the functionality of blood neutrophils and peritoneal macrophages in the DSE group. Interval training increased all functionality parameters of peritoneal macrophages in the IT group. Interval training also led to a twofold increase in the proliferation of mesenteric lymphocytes after 6 weeks of exercise in the DIT group. Low-volume high-intensity physical exercise attenuates hyperglycemia and dislipidemia induced by type 1 diabetes, and induces changes in the functionality of innate and acquired immunity.

Changes in phosphocreatine concentration of skeletal muscle during high-intensity intermittent exercise in children and adults

The aim of the present study was to test the hypotheses that a greater oxidative capacity in children results in a lower phosphocreatine (PCr) depletion, a faster PCr resynthesis and a lower muscle acidification during high-intensity intermittent exercise compared to adults. Sixteen children (9.4 ± 0.5 years) and 16 adults (26.1 ± 0.3 years) completed a protocol consisting of a dynamic plantar flexion (10 bouts of 30-s exercise at 25 % of one repetition maximum separated by 20-s recovery), followed by 10 min of passive recovery. Changes of PCr, ATP, inorganic phosphate, and phosphomonoesters were measured by means of (31)Phosphorous-magnetic resonance spectroscopy during and post-exercise. Average PCr (percentage of [PCr] at initial rest (%[PCr]i)) at the end of the exercise (adults 17 ± 12 %[PCr]i, children 38 ± 17 %[PCr]i, P < 0.01) and recovery periods (adults 37 ± 14 %[PCr]i, children 57 ± 17 %[PCr]i, P < 0.01) was significantly lower in adults compared to children, induced by a stronger PCr decrease during the first exercise interval (adults -73 ± 10 %[PCr]i, children -55 ± 15 %[PCr]i, P < 0.01). End-exercise pH was significantly higher in children compared to adults (children 6.90 + 0.20, -0.14; adults 6.67 + 0.23, -0.15, P < 0.05). From our results we suggest relatively higher rates of oxidative ATP formation in children's muscle for covering the ATP demand of high-intensity intermittent exercise compared to adults, enabling children to begin each exercise interval with significantly higher PCr concentrations and leading to an overall lower muscle acidification.

Sprint exercise enhances skeletal muscle p70S6k phosphorylation and more so in women than in men

Sprint exercise is characterized by repeated sessions of brief intermittent exercise at a high relative workload. However, little is known about the effect on mTOR pathway, an important link in the regulation of muscle protein synthesis. An earlier training study showed a greater increase in muscle fibre cross-sectional area in women than men. Therefore, we tested the hypothesis that the activation of mTOR signalling is more pronounced in women than in men. Healthy men (n=9) and women (n=8) performed three bouts of 30-s sprint exercise with 20-min rest in between. Multiple blood samples were collected over time, and muscle biopsy specimens were obtained at rest and 140 min after the last sprint. Serum insulin increased by sprint exercise and more so in women than in men [gender (g) × time (t)]: P=0.04. In skeletal muscle, phosphorylation of Akt increased by 50% (t, P=0.001) and mTOR by 120% (t, P=0.002) independent of gender. The elevation in p70S6k phosphorylation was larger in women (g × t, P=0.03) and averaged 230% (P=0.006) as compared to 60% in men (P=0.04). Phosphorylation rpS6 increased by 660% over time independent of gender (t, P=0.003). Increase in the phosphorylation of p70S6k was directly related to increase in serum insulin (r=0.68, P=0.004). It is concluded that repeated 30-s all-out bouts of sprint exercise separated by 20 min of rest increases Akt/mTOR signalling in skeletal muscle. Secondly, signalling downstream of mTOR was stronger in women than in men after sprint exercise indicated by the increased phosphorylation of p70S6k.

Sprint exercise enhances skeletal muscle p70S6k phosphorylation and more so in females than in males

Aim: Sprint exercise is characterized by repeated sessions of brief intermittent exercise at a high relative workload. However, little is known about the effect on mTOR pathway, an important link in regulation of muscle protein synthesis. An earlier training study showed a greater increase in muscle fibre cross sectional area in females than males. Therefore, we tested the hypothesis that activation of mTOR signalling is more pronounced in females than in males. Healthy males (n=9) and females (n=8) performed three bouts of 30-s sprint exercise with 20 min rest between. Methods: Multiple blood samples were collected over time and muscle biopsy specimens were obtained at rest and 140 min after the last sprint. Results: Serum insulin increased by sprint exercise and more so in females than in males (gender (g) x time (t):P=0.04. In skeletal muscle, phosphorylation of Akt increased by 50% (t, P=0.001) and mTOR by 120% (t, P=0.002) independent of gender. The elevation in p70S6k phosphorylation was larger in females (g x t, P=0.03) and averaged 230% (P=0.006) as compared to 60% in males (P=0.04). Phosphorylation rpS6 increased by 660% over time independent of gender (t, P=0.003). Increase in phosphorylation of p70S6k was directly related to increase in serum insulin (r=0.68, P=0.004). Conclusion: It is concluded that repeated 30-s all out bouts of sprint exercise separated by 20 min of rest, increases Akt/mTOR signalling in skeletal muscle. Secondly, signalling downstream of mTOR was stronger in females than in males after sprint exercise indicated by increased phosphorylation of p70S6k.

Is sprint exercise a leptin signaling mimetic in human skeletal muscle?

This study was designed to determine whether sprint exercise activates signaling cascades linked to leptin actions in human skeletal muscle and how this pattern of activation may be interfered by glucose ingestion. Muscle biopsies were obtained in 15 young healthy men in response to a 30-s sprint exercise (Wingate test) randomly distributed into two groups: the fasting (n = 7, C) and the glucose group (n = 8, G), who ingested 75 g of glucose 1 h before the Wingate test. Exercise elicited different patterns of JAK2, STAT3, STAT5, ERK1/2, p38 MAPK phosphorylation, and SOCS3 protein expression during the recovery period after glucose ingestion. Thirty minutes after the control sprint, STAT3 and ERK1/2 phosphorylation levels were augmented (both, P < 0.05). SOCS3 protein expression was increased 120 min after the control sprint but PTP1B protein expression was unaffected. Thirty and 120 min after the control sprint, STAT5 phosphorylation was augmented (P < 0.05). Glucose abolished the 30 min STAT3 and ERK1/2 phosphorylation and the 120 min SOCS3 protein expression increase while retarding the STAT5 phosphorylation response to sprint. Activation of these signaling cascades occurred despite a reduction of circulating leptin concentration after the sprint. Basal JAK2 and p38 MAPK phosphorylation levels were reduced and increased (both P < 0.05), respectively, by glucose ingestion prior to exercise. During recovery, JAK2 phosphorylation was unchanged and p38 MAPK phosphorylation was transiently reduced when the exercise was preceded by glucose ingestion. In conclusion, sprint exercise performed under fasting conditions is a leptin signaling mimetic in human skeletal muscle.

Age- and Gender-Associated Variation in Maximal-Intensity Exercise Performance in Adolescent Rowers

We aimed to (1) characterize the 30-s maximal-intensity exercise performance using a Wingate rowing test in 12- to 18-year-old female rowers grouped by age, and (2) to compare the obtained performance indicators (i. e., mean- and maximal power output) with those of male rowers (n=297) of the same age. 193 female rowers (mean±SD: 14.9±1.9 years; range: 12.0-18.9 years) completed a maximal 30-s test on a rowing ergometer. An ANOVA with Bonferroni post-hoc analyses was used to compare the performances among the age groups, and age-related increases in performance up to age 15 with a plateau in performance thereafter, were observed. The age-related increases in performance were reduced by approximately one half when the effects of body mass were statistically removed with the use of ANCOVA. Gender-associated differences in Wingate rowing test performance were observed from age 13 (p<0.05, +19-22% in favour of males) and increased thereafter. Between the ages of 16 and 18, these differences appeared to change very little and ranged between ∼50-60% (all p<0.001). This pattern of gender-associated differences was similar, although the differences were reduced in relative terms by about one third, when the body mass of rowers of both sexes was statistically removed using ANCOVA analyses.

Reduction in plasma leucine after sprint exercise is greater in males than in females

There is a pronounced gender difference in the accumulation of plasma ammonia after sprint exercise. Ammonia is a key intermediate in amino acid metabolism, which implies that gender-related differences in plasma and muscle amino acid concentrations after sprint exercise exist. To study this, three bouts of 30-s sprint exercise were performed by healthy females (n=8) and males (n=6). Blood leucine and muscle leucine were collected over the exercise period. Basal arterial plasma and skeletal muscle leucine were 40% higher in males than females (P<0.010 and P<0.020). Plasma, but not muscle, leucine decreased by sprint exercise and more so in males than females (g × t: P=0.025). Increase in ammonia was higher in males than females in both plasma and muscle (g × t: P<0.001 and P=0.003). An opposite pattern was shown for plasma glutamine, where an increase was found in females (P<0.001), but not in males. In conclusion, the lower plasma ammonia after sprint exercise in females seems to be explained by a lower accumulation of ammonia in skeletal muscle and by a buffering of ammonia in the form of glutamine in females. The greater reduction in plasma leucine in males seems to be related to their greater increase in muscle ammonia after sprint exercise.

SIRT1, AMP-activated protein kinase phosphorylation and downstream kinases in response to a single bout of sprint exercise: influence of glucose ingestion

This study was designed to examine potential in vivo mechanisms of AMP-activated protein kinase (AMPK) phosphorylation inhibition and its downstream signaling consequences during the recovery period after a single bout of sprint exercise. Sprint exercise induces Thr(172)-AMPK phosphorylation and increased PGC-1alpha mRNA, by an unknown mechanism. Muscle biopsies were obtained in 15 young healthy men in response to a 30-s sprint exercise (Wingate test) randomly distributed into two groups: the fasting (n = 7, C) and the glucose group (n = 8, G), who ingested 75 g of glucose 1 h before exercising to inhibit AMPKalpha phosphorylation. Exercise elicited different patterns of Ser(221)-ACCbeta, Ser(473)-Akt and Thr(642)-AS160 phosphorylation, during the recovery period after glucose ingestion. Thirty minutes after the control sprint, Ser(485)-AMPKalpha1/Ser(491)-AMPKalpha2 phosphorylation was reduced by 33% coinciding with increased Thr(172)-AMPKalpha phosphorylation (both, P < 0.05). Glucose abolished the 30-min Thr(172)-AMPKalpha phosphorylation. Ser(221)-ACCbeta phosphorylation was elevated immediately following and 30 min after exercise in C and G, implying a dissociation between Thr(172)-AMPKalpha and Ser(221)-ACCbeta phosphorylation. Two hours after the sprint, PGC-1alpha protein expression remained unchanged while SIRT1 (its upstream deacetylase) was increased. Glucose ingestion abolished the SIRT1 response without any significant effect on PGC-1alpha protein expression. In conclusion, glucose ingestion prior to a sprint exercise profoundly affects Thr(172)-AMPKalpha phosphorylation and its downstream signaling during the recovery period.

Ten‐second exercise is superior to 30‐second exercise for post‐exercise facilitation in diagnosing Lambert–Eaton myasthenic syndrome

An incremental response after brief exercise or high-rate stimulation on the repetitive nerve stimulation (RNS) test is a critical diagnostic criterion for Lambert-Eaton myasthenic syndrome (LEMS). This prospective study was performed to determine what duration of exercise shows the highest diagnostic sensitivity for LEMS. The compound muscle action potential amplitude in the abductor digiti quinti muscle was obtained at rest and after 5 s, 10 s, 15 s, 20 s, 25 s, and 30 s of exercise. Incremental responses were compared for the different exercise durations in 24 studies performed in nine LEMS patients. The increment was highest with 5-s and 10-s exercises (244%-243%) and lowest with 30-s exercise (84%). A gradual decrease in the increment was noted from 5- to 30-s exercise. A significant difference in the increment was noted between 5- to 10-s and 20-s to 30-s exercise. There was significantly higher diagnostic sensitivity with the 10-s exercise compared with 30-s exercise at 100% increment and 60% increment levels. Higher increment and diagnostic sensitivity were achieved with 10-s exercise than with 30-s exercise. Thus, 10-s exercise should be the standard protocol for the RNS test for LEMS.

Efficacy of Selected Workloads in Identifying Anaerobic Power Using the Wingate Anaerobic Test

0797 The Wingate anaerobic test was first developed in 1977 as a laboratory test to assess musculoskeletal anaerobic power. The test was performed on a modified bicycle ergometer at a workload equivalent to 7.5% (0.075 Kp/kg) of the performer's body weight and required one all-out 30-s exercise session. Since then, studies have recommended optimum loads for obtaining peak power as 9.5% of the performer's body weight for untrained adult males and 9.0% of the performer's body weight for untrained adult females. It has been suggested that the test is insensitive to small adjustments in resistance load and has large individual variability around the resistance producing maximal power values. PURPOSE: To examine peak anaerobic power (Pp) and mean anaerobic power (Pm) at the original and the new recommended workloads, as well as one workload above and one below these resistances. METHODS: Twenty-four sedentary college men (n = 12) and women (n = 12), 19 to 29 years of age (for males, 22.3 ± 1.3 yrs; for females, 22.0 ± 2.5 yrs) were assessed on a Monark Ergomedic 894E cycle ergometer using the Wingate protocol at workloads equivalent to 6.5%, 7.5%, 9.5%, and 11.5% of the performers' body weights. RESULTS: For Pp, a main effect for gender was found (P< .05); thus, males and females were analyzed separately. In males, repeated measures analysis of variance with Bonferroni correction identified Pp at 9.5% to be significantly greater than Pp at 6.5% (P< .001), 7.5% (P< .01), and 11.5% (P< .05). For females, Pp was again produced at 9.5% and found to be significantly (P< .01) greater than Pp at 6.5% or 7.5%, but not from Pp measured at 11.5% (P = .166). A main effect for gender was not found for Pm (P = .068); therefore, male and female data were combined. Pairwise comparisons with Bonferroni adjustment identified Pm at 9.5% to be significantly greater than Pm at 6.5% (p< .001), 7.5% (P< .01), and 11.5% (P< .01). No other groups were significantly different from each other. CONCLUSIONS: Resistance loads that vary by 2% of the performer's body weight from optimum loads during the Wingate anaerobic test elicit peak and mean anaerobic power values significantly lower than power values obtained at the currently recommended loads for this population.

Efficacy of Selected Workloads in Identifying Anaerobic Power Using the Wingate Anaerobic Test

0797 The Wingate anaerobic test was first developed in 1977 as a laboratory test to assess musculoskeletal anaerobic power. The test was performed on a modified bicycle ergometer at a workload equivalent to 7.5% (0.075 Kp/kg) of the performer's body weight and required one all-out 30-s exercise session. Since then, studies have recommended optimum loads for obtaining peak power as 9.5% of the performer's body weight for untrained adult males and 9.0% of the performer's body weight for untrained adult females. It has been suggested that the test is insensitive to small adjustments in resistance load and has large individual variability around the resistance producing maximal power values. PURPOSE: To examine peak anaerobic power (Pp) and mean anaerobic power (Pm) at the original and the new recommended workloads, as well as one workload above and one below these resistances. METHODS: Twenty-four sedentary college men (n = 12) and women (n = 12), 19 to 29 years of age (for males, 22.3 ± 1.3 yrs; for females, 22.0 ± 2.5 yrs) were assessed on a Monark Ergomedic 894E cycle ergometer using the Wingate protocol at workloads equivalent to 6.5%, 7.5%, 9.5%, and 11.5% of the performers' body weights. RESULTS: For Pp, a main effect for gender was found (P< .05); thus, males and females were analyzed separately. In males, repeated measures analysis of variance with Bonferroni correction identified Pp at 9.5% to be significantly greater than Pp at 6.5% (P< .001), 7.5% (P< .01), and 11.5% (P< .05). For females, Pp was again produced at 9.5% and found to be significantly (P< .01) greater than Pp at 6.5% or 7.5%, but not from Pp measured at 11.5% (P = .166). A main effect for gender was not found for Pm (P = .068); therefore, male and female data were combined. Pairwise comparisons with Bonferroni adjustment identified Pm at 9.5% to be significantly greater than Pm at 6.5% (p< .001), 7.5% (P< .01), and 11.5% (P< .01). No other groups were significantly different from each other. CONCLUSIONS: Resistance loads that vary by 2% of the performer's body weight from optimum loads during the Wingate anaerobic test elicit peak and mean anaerobic power values significantly lower than power values obtained at the currently recommended loads for this population.

Altered energetic properties in skeletal muscle of men with well-controlled insulin-dependent (type 1) diabetes.

This study asked whether the energetic properties of muscles are changed by insulin-dependent diabetes mellitus (or type 1 diabetes), as occurs in obesity and type 2 diabetes. We used (31)P magnetic resonance spectroscopy to measure glycolytic flux, oxidative flux, and contractile cost in the ankle dorsiflexor muscles of 10 men with well-managed type 1 diabetes and 10 age- and activity-matched control subjects. Each subject performed sustained isometric muscle contractions lasting 30 and 120 s while attempting to maintain 70-75% of maximal voluntary contraction force. An altered glycolytic flux in type 1 diabetic subjects relative to control subjects was apparent from significant differences in pH in muscle at rest and at the end of the 120-s bout. Glycolytic flux during exercise began earlier and reached a higher peak rate in diabetic patients than in control subjects. A reduced oxidative capacity in the diabetic patients' muscles was evident from a significantly slower phosphocreatine recovery from a 30-s exercise bout. Our findings represent the first characterization of the energetic properties of muscle from type 1 diabetic patients. The observed changes in glycolytic and oxidative fluxes suggest a diabetes-induced shift in the metabolic profile of muscle, consistent with studies of obesity and type 2 diabetes that point to common muscle adaptations in these diseases.