Relative Exercise Intensity Research Articles

Effects of Blood Withdrawal on Cardiac, Hemodynamic, and Pulmonary Responses to a Moderate Acute Workload in Healthy Middle‐Aged and Older Females

Background The fundamental role of blood volume (BV) on cardiorespiratory fitness has been well studied in males during maximal exercise. However, understanding the importance of BV on key physiological responses to a submaximal workload in females has yet to be elucidated. The objective of this study was to investigate the effects of blood withdrawal on cardiac, hemodynamic, and pulmonary responses to submaximal exercise in females. We hypothesized that blood withdrawal would reduce cardiac filling and stroke volume (SV) which would result in a compensatory increase in heart rate (HR) to preserve cardiac output (Q) at a fixed submaximal workload. Methods 30 healthy females (63.8 ± 8.3 yr) were recruited for this study. Transthoracic echocardiography, non-invasive blood pressure monitoring, and a peak oxygen uptake (VO2peak) test were performed at a 100 W submaximal workload prior to and immediately after a 10 % reduction of BV. Primary outcomes included left ventricular end-diastolic volume (LVEDV), SV, Q, HR, and VO2peak. BV was determined using an established carbon monoxide rebreathing technique. Results BV of subjects ranged from 3.8 to 6.6 L, with an average 10 % reduction of 0.5 ± 0.1 L. Following blood withdrawal, both LVEDV (P ≤ 0.030) and SV (P < 0.019) were reduced while Q was unchanged (P = 0.139) due to an augmented HR (P < 0.026). Submaximal hemodynamic variables including MAP (P < 0.015), SBP (P < 0.005), and DBP (P < 0.038) were reduced while VO2peak was unaltered (P = 0.250). Conclusion Blood withdrawal results in marked reductions in cardiac filling with compensatory chronotropic responses that preserve Q at an acute moderate submaximal workload in healthy females. BV thus determines the relative exercise intensity, as typically determined by HR, of submaximal efforts in this population.

Effect of Player Role and Competition Level on Player Demands in Basketball.

This study compared basketball training and match demands between player roles (starters, in-rotation bench players, out-rotation bench players) and between competition levels (semi-professional, professional). Thirty-seven players from one professional women’s team, one semi-professional women’s team, and one semi-professional men’s team wore accelerometers during training and matches throughout a competitive season. All teams were used for player role comparisons and the women’s teams were used to compare competition levels. Match and training session average intensity and volume, and durations of relative exercise intensities (inactive, light, moderate-vigorous, maximal, supramaximal) were calculated. Compared to out-rotation bench players, starters experienced twice the average match intensity and volume, spent 50% less match time being inactive, and spent 1.7–4.2× more match time in all other activity categories (p < 0.01). Compared to in-rotation bench players, starters experienced 1.2× greater average match intensity and volume, spent 17% less match time being inactive, and spent 1.4–1.5× more match time performing moderate-vigorous and maximal activity (p < 0.01). No differences in match demands were found between women’s competition levels, however the professional team experienced double the cumulative weekly training volume of the semi-professional team and spent 1.6–2.1× more cumulative weekly time in all activity categories (p < 0.01). To improve performance and reduce injury risk, players should prepare for the greatest match demands they could encounter during a season while considering potential changes to their role. Additionally, players might need their training volume managed when transitioning from a semi-professional to a professional season to reduce the injury risk from sharp increases in training demands.

Exercício aeróbio, de resistência ou combinado: que tipo mais contribui para melhorar a função endotelial? Resenha da metanálise de Ashor et al.

Introdução: Como parte da Edição Especial de 2020 I, a Revista de Educação Física / Journal of Physical Education (REF/JPE) está trazendo aspectos científicos da prática de atividade física relacionados à pandemia de CoViD-19.&#x0D; Objetivo: Apresentar e indicar aos leitores da REF/JPE, a leitura do estudo de revisão, com metanálise, de Ashor et al., publicado em um periódico internacional. Baseado em estudos de ensaio clínico randomizados, os efeitos do exercício aeróbio, de resistência e combinado de ambos sobre a função endotelial foram comparados. A literatura recente indica que a CoViD-19 envolve o endotélio no processo, nesse sentido, avaliar qual o tipo de exercício melhora sua função é de alta relevância.&#x0D; Conclusão: Todas as modalidades de exercício (aeróbio, resistidos e combinados) aumentaram a função endotelial significativamente em comparação com os grupos controle. Os maiores efeitos foram observados com os exercícios aeróbicos, seguidos pelos exercícios combinados e resistidos. Em exercícios aeróbios, houve uma relação dose-resposta significativa entre a intensidade tanto absoluta quanto relativa do exercício aeróbio e a função endotelial. Em exercícios resistidos a correlação positiva foi encontrada na frequência e não na intensidade. Os resultados foram discutidos pelos autores, recomenda-se a leitura.

Aerobic Training Modulates the Increase in Plasma Concentrations of Cytokines in response to a Session of Exercise.

Acute physical exercise can modulate immune function. For example, acute exercise is known to increase the circulating concentration of cytokines. Exercise is also known to modulate immune function chronically. It is not known whether exercise training can result in training of the immune system. Here, we investigated the effects of six weeks of aerobic training on cytokine responses induced by acute exercise until fatigue. Twelve healthy men performed a fatiguing exercise at the anaerobic threshold (AT) intensity. After the training period, the participants performed another bout of acute exercise at the same duration and intensity of the pretraining situation. The analysis was made at the beginning, end, and at 10, 30, and 60 minutes during the recovery period. Training at AT induced a gain of 11.2% of exercise capacity. Before training, a single bout of acute exercise induced a significant increase in plasma levels of cytokines, including IL-6, TNF-α, sTNFR1, IL-10, CXCL10, BDNF, leptin, resistin, and adiponectin. After six weeks of aerobic training, levels of IL-6, sTNFR1, BDNF, and leptin increased to a lesser extent after an acute bout exercise at the same absolute intensity as the pretraining period. Responses to the same relative exercise intensity were similar to those observed before exercise. These results show that aerobic training is associated with training of acute immune responses to acute exercise until fatigue.

Physiological stress of basketball referees during a national competition

abstract The aim of this study was to examine the physiological demands of seven referees during a national basketball competition. We recorded heart rate (HR), relative exercise intensity as a percentage of age – predicted maximum HR (HRmax), proportion of playing time within the exercise intensity categories defined by the ACSM during each of the tournament matches for each referee per period, as well as the entire game. None of the variables shows significant differences between periods. Based on a format of three referees per match, referees worked with an average HR of 150 bpm (range 110-181 bpm) for each quarter of the match, which equals a relative intensity&gt; 70% of HRmax for most (∼76%) of each quarter. Other studies will assist in developing appropriate training programs for elite basketball referees to maintain and / or maximize performance.

Effects of endurance exercise under hypoxia on acid-base and ion balance in healthy males.

[Purpose]This study was performed to investigate the acid-base and ion balance at rest and after exercise in healthy males under normoxia, moderate hypoxia, and severe hypoxia.[Methods]Ten healthy Korean males completed three different trials on different days, comprising exercise under normoxia (FiO2 = 20.9%, N trial), moderate hypoxia (FiO2 = 16.5%, MH trial), and severe hypoxia (FiO2 = 12.8%, SH trial). They undertook endurance exercise for 30 min on a cycle ergometer at the same relative exercise intensity equivalent to 80% maximal heart rate under all conditions. Capillary blood samples were obtained to determine acid-base and ion balance at rest and after exercise.[Results]Exercise-induced blood lactate elevations were significantly increased as hypoxic conditions became more severe; SH > MH > N trials (P = 0.003). After exercise, blood glucose levels were significantly higher in the SH trial than in the N and MH trials (P = 0.001). Capillary oxygen saturation (SCO2) levels were significantly lowered as hypoxic conditions became more severe; SH > MH > N trials (P < 0.001). The pH levels were significantly lower in the MH trial than that in the N trial (P = 0.010). Moreover, HCO3- levels were significantly lower in the SH trial than in the N trial, with significant interaction (P = 0.003). There were no significant differences in blood Na+, K+, and Ca2+ levels between the trials.[Conclusion]MH and SH trials induced greater differences in glucose, lactate, SCO2, pH, and HCO3- levels in capillary blood compared to the N trial. Additionally, lactate, SCO2, and HCO3- levels showed greater changes in the SH trial than in the MH trial. However, there were no significant differences in Na+, K+, and Ca2+ levels in MH and SH trials compared to the N trial.

Sex differences in fatigability following exercise normalised to the power-duration relationship.

Knee-extensors demonstrate greater fatigue resistance in females compared to males during single-limb and whole-body exercise. For single-limb exercise, the intensity-duration relationship is different between sexes, with females sustaining a greater relative intensity of exercise. This study established the power-duration relationship during cycling, then assessed fatigability during critical power-matched exercise within the heavy and severe intensity domains. When critical power and the curvature constant were expressed relative to maximal ramp test power, no sex difference was observed. No sex difference in time to task failure was observed in either trial. During heavy and severe intensity cycling, females experienced lesser muscle de-oxygenation. Following both trials, females experienced lesser reductions in knee-extensor contractile function, and following heavy intensity exercise, females experienced less reduction in voluntary activation. These data demonstrate that whilst the relative power-duration relationship is not different between males and females, the mechanisms of fatigability during critical power-matched exercise are mediated by sex. Due to morphological differences, females demonstrate greater fatigue resistance of locomotor muscle during single-limb and whole-body exercise modalities. Whilst females sustain a greater relative intensity of single-limb, isometric exercise than males, limited investigation has been performed during whole-body exercise. Accordingly, this study established the power-duration relationship during cycling in 18 trained participants (eight females). Subsequently, constant-load exercise was performed at critical power (CP)-matched intensities within the heavy and severe domains, with the mechanisms of fatigability assessed via non-invasive neurostimulation, near-infrared spectroscopy and pulmonary gas exchange during and following exercise. Relative CP (72±5 vs. 74±2% Pmax , P=0.210) and curvature constant (51±11 vs. 52±10JPmax-1 , P=0.733) of the power-duration relationship were similar between males and females. Subsequent heavy (P=0.758) and severe intensity (P=0.645) exercise time to task failures were not different between sexes. However, females experienced lesser reductions in contractile function at task failure (P≤0.020), and greater vastus lateralis oxygenation (P≤0.039) during both trials. Reductions in voluntary activation occurred following both trials (P<0.001), but were less in females following the heavy trial (P=0.036). Furthermore, during the heavy intensity trial only, corticospinal excitability was reduced at the cortical (P=0.020) and spinal (P=0.036) levels, but these reductions were not sex-dependent. Other than a lower respiratory exchange ratio in the heavy trial for females (P=0.039), no gas exchange variables differed between sexes (P≥0.052). Collectively, these data demonstrate that whilst the relative power-duration relationship is not different between males and females, the mechanisms of fatigability during CP-matched exercise above and below CP are mediated by sex.

Alterations in Cardiac Function Following Endurance Exercise Are Not Duration Dependent.

Cardiac function has been shown to transiently decrease following prolonged exercise, with greater durations related to increased impairment. However, the prospective assessment of exercise duration on cardiac performance is rare, and the influence of relative exercise intensity is typically not assessed in relation to these changes. The aim of this study was to determine whether progressively longer running distances over the same course would elicit greater cardiac impairment. The present investigation examined cardiac alterations in 49 athletes, following trail-running races of 25, 50, 80, and 160 km, performed on the same course on the same day. Echocardiography, including conventional and speckle tracking imaging, was performed with legs-raised to 60° to mitigate alterations in preload both pre- and post-race. Race-intensities were monitored via heart rate (HR). Following the races, mean arterial pressure (Δ−11 ± 7 mmHg, P < 0.0001), and HR (Δ19 ± 14 bpm, P < 0.0001) were altered independent of race distance. Both left and right ventricular (LV and RV) diastolic function were reduced (ΔLV E/A −0.54 ± 0.49, P < 0.0001; ΔRV A’ + 0.02 ± 0.04 m/s, P = 0.01) and RV systolic function decreased (ΔTAPSE −0.25 ± 0.9 cm, P = 0.01), independent of race distance. Cardiac impairment was not apparent using speckle tracking analysis with cubic spline interpolation. While race duration was unrelated to cardiac alterations, increased racing HR was related to greater RV base dilation (r = −0.37, P = 0.03). Increased time spent at higher exercise intensities was related to reduced LV ejection fraction following 25 km (r = −0.81, P = 0.03), LV systolic strain rate following 50 km (r = 0.59, P = 0.04), and TAPSE (r = −0.81, P = 0.03) following 80 km races. Increased running duration did not affect the extent of exercise-induced cardiac fatigue, however, intensity may be a greater driver of cardiac alterations.

Heart rate acceleration at relative workloads during treadmill and overground running for tracking exercise performance during functional overreaching

Maximal rate of heart rate (HR) increase (rHRI) as a measure of HR acceleration during the transition from rest to exercise, or during an increase in workload, tracks exercise performance. rHRI assessed at relative rather than absolute workloads may track performance better, and a field test would increase applicability. This study therefore aimed to evaluate the sensitivity of rHRI assessed at individualised relative workloads during treadmill and overground running for tracking exercise performance. Treadmill running performance (5 km time trial; 5TTT) and rHRI were assessed in 11 male runners following 1 week of light training (LT), 2 weeks of heavy training (HT) and a 10-day taper (T). rHRI was the first derivative maximum of a sigmoidal curve fit to HR data collected during 5 min of treadmill running at 65% peak HR (rHRI65%), and subsequent transition to 85% peak HR (rHRI85%). Participants ran at the same speeds overground, paced by a foot-mounted accelerometer. Time to complete 5TTT likely increased following HT (ES = 0.14 ± 0.03), and almost certainly decreased following T (ES = − 0.30 ± 0.07). Treadmill and field rHRI65% likely increased after HT in comparison to LT (ES ≤ 0.48 ± 0.32), and was unchanged at T. Treadmill and field rHRI85% was unchanged at HT in comparison to LT, and likely decreased at T in comparison to LT (ES ≤ − 0.55 ± 0.50). 5TTT was not correlated with treadmill or field rHRI65% or rHRI85%. rHRI65% was highly correlated between treadmill and field tests across LT, HT and T (r ≥ 0.63), but correlations for rHRI85% were trivial to moderate (r ≤ 0.42). rHRI assessed at relative exercise intensities does not track performance. rHRI assessed during the transition from rest to running overground and on a treadmill at the same running speed were highly correlated, suggesting that rHRI can be validly assessed under field conditions at 65% of peak HR.

Carbohydrate Hydrogel Products Do Not Improve Performance or Gastrointestinal Distress During Moderate-Intensity Endurance Exercise.

The benefits of ingesting exogenous carbohydrate (CHO) during prolonged exercise performance are well established. A recent food technology innovation has seen sodium alginate and pectin included in solutions of multiple transportable CHO, to encapsulate them at pH levels found in the stomach. Marketing claims include enhanced gastric emptying and delivery of CHO to the muscle with less gastrointestinal distress, leading to better sports performance. Emerging literature around such claims was identified by searching electronic databases; inclusion criteria were randomized controlled trials investigating metabolic and/or exercise performance parameters during endurance exercise >1hr, with CHO hydrogels versus traditional CHO fluids and/or noncaloric hydrogels. Limitations associated with the heterogeneity of exercise protocols and control comparisons are noted. To date, improvements in exercise performance/capacity have not been clearly demonstrated with ingestion of CHO hydrogels above traditional CHO fluids. Studies utilizing isotopic tracers demonstrate similar rates of exogenous CHO oxidation, and subjective ratings of gastrointestinal distress do not appear to be different. Overall, data do not support any metabolic or performance advantages to exogenous CHO delivery in hydrogel form over traditional CHO preparations; although, one study demonstrates a possible glycogen sparing effect. The authors note that the current literature has largely failed to investigate the conditions under which maximal CHO availability is needed; high-performance athletes undertaking prolonged events at high relative and absolute exercise intensities. Although investigations are needed to better target the testimonials provided about CHO hydrogels, current evidence suggests that they are similar in outcome and a benefit to traditional CHO sources.

Exogenous glucose oxidation during endurance exercise in hypoxia.

PurposeEndurance exercise in hypoxia promotes carbohydrate (CHO) metabolism. However, detailed CHO metabolism remains unclear. The purpose of this study was to evaluate the effects of endurance exercise in moderate hypoxia on exogenous glucose oxidation at the same energy expenditure or relative exercise intensity.MethodsNine active healthy males completed three trials on different days, consisting of 30 min of running at each exercise intensity: (a) exercise at 65% of normoxic maximal oxygen uptake in normoxia [NOR, fraction of inspired oxygen (FiO2) = 20.9%, 10.6 ± 0.3 km/h], (b) exercise at the same relative exercise intensity with NOR in hypoxia (HYPR, FiO2 = 14.5%, 9.4 ± 0.3 km/h), and (c) exercise at the same absolute exercise intensity with NOR in hypoxia (HYPA, FiO2 = 14.5%, 10.6 ± 0.3 km/h). The subjects consumed 113C‐labeled glucose immediately before exercise, and expired gas samples were collected during exercise to determine 13C‐excretion (calculated by 13CO2/12CO2).ResultsThe exercise‐induced increase in blood lactate was significantly augmented in the HYPA than in the NOR and HYPR (p = .001). HYPA involved a significantly higher respiratory exchange ratio (RER) during exercise compared with the other two trials (p < .0001). In contrast, exogenous glucose oxidation (13C‐excretion) during exercise was significantly lower in the HYPA than in the NOR (p = .03). No significant differences were observed in blood lactate elevation, RER, or exogenous glucose oxidation between NOR and HYPR.ConclusionEndurance exercise in moderate hypoxia caused a greater exercise‐induced blood lactate elevation and RER compared with the running exercise at same absolute exercise intensity in normoxia. However, exogenous glucose oxidation (13C‐excretion) during exercise was attenuated compared with the same exercise in normoxia.

Acute Exercise Increases Pain Threshold And Subjective Psychoactive Mood State

Prescription pain medication can be addictive and have long-term health consequences. Alternative pain-relieving strategies are becoming increasingly sought after. Exercise is known to have a pain-relieving effect which is thought to be mediated through the dopaminergic system. PURPOSE: To examine the relationships between minimum pain threshold (MPT), exercise blood lactate (EBL), and the self-reported psychoactive effects of exercise based on questions from the Morphine-Benzedrine Group, Morphine and Excitement subscales of the Addiction Research Center Inventory (ARCI) following acute exercise in college aged students. METHODS: Twelve college aged students (age = 20.9 ± 0.5yr) underwent 5 minutes of light leg cycling as a warmup. Following the warmup, they cycled for 20 minutes at 8 METS with an additional 5-minute cooldown. Measurements were taken prior to exercise and just before the cool down. EBL was collected as a measure of relative exercise intensity. The MPT was measured using a Wagner “Pain Test” algometer on the extensor carpi radialis. Results were assessed using a Student’s T-Test. RESULTS: Following exercise the MPT was increased by 62.1% ± 2.8 (P<0.001). Women had a greater increase in MPT (25.7 ± 9.1%) relative to men (15.8 ± 9.4%; P<0.05). EBL increased from an average of 1.8 ± 0.6 mmol/L at baseline to 4.1 ± 0.7 mmol/L following exercise (P<0.01). There was a positive linear correlation between MPT and EBL (r2=0.59; P<0.05). Indicating greater EBL levels were related to increased MPT. Positive responses from the ARCI subscale increased by 27 ± 3.3% following exercise (P<0.05). There was no effect of sex nor EBL on positive responses on the ARCI. CONCLUSIONS: These data suggest moderate intensity exercise can increase MPT and to a greater extent in women. Further, MPT correlated with increased EBL indicating that greater relative exercise intensity may modulate a greater increase MPT. Moderate intensity exercise increased positive responses on the ARCI providing evidence that the dopaminergic system may drive changes to MPT. However, positive responses did not correlate to EBL which may suggest another variable may augment pain reduction with increased exercise intensity.

Correspondence Between Indexes Of Maximal Fat Oxidation From Ramp Vs Steady-state Protocols In Postmenopausal Women

Maximal fat oxidation (MFO, in g-1·min-1) is an index of metabolic flexibility and the relative exercise intensity at MFO (FATmax, as % maximum oxygen consumption (VO2max)) is used for exercise prescription for weight loss and metabolic health. The time-consuming, steady-state protocol required for MFO/FATmax determination hinders the extensive use of these indexes. Alternative, ramp testing has been validated for MFO/FATmax determination in healthy, young males only. PURPOSE: to validate ramp testing for MFO/FATmax measure in post-menopausal women. METHODS: 18 sedentary, postmenopausal women (54±4 years; 4±3 years from menopause; 22±3 BMI) performed on a cycle ergometer: i) a ramp incremental test; ii) steady-state trials at 40, 50, 60, 70 and 80% of the VO2max as determined by the incremental test. We measured VO2, respiratory exchange ratio (R) and heart rate (HR). Based on VO2 and R from the ramp test (breath-by breath data) and steady-state protocol (5th minute of each trial) we measured absolute fat oxidation (FO, in g-1·min-1); then, we determined MFO in absolute units (in g-1·min-1) and the relative intensity corresponding to MFO, i.e. FATmax, that was expressed relative to VO2max and directly determined maximal HR (HRmax). MFO and FATmax from the ramp (rMFO and rFATmax) were compared to the values from the steady-state protocol (ssMFO and ssFATmax) by paired t-Test. RESULTS: The ssMFO was significantly lower than rMFO (0.39±0.13 vs 0.19±0.07 g.min-1 p<0.001). On the contrary, the rFATmax and ssFATmax occurred at an identical %VO2max (45±6 vs 47±7%VO2max p=0.17) and %HRmax (61±6 vs 62±6% HRmax p=0.54). CONCLUSIONS: In agreement with previous studies conducted in young males, our data confirm that only steady-state protocols allow accurate MFO quantification. On the contrary, accurate measures of FATmax can be obtained indifferently from both ramp and steady-state protocols in post-menopausal women. Therefore, ramp testing offers a valid alternative to more time-consuming steady-state protocols for the identification of optimal exercise intensity for weight loss and metabolic health. Time-efficient testing strategies have a high practical value for longitudinal/large-scale evaluation of fat metabolism in postmenopausal women offering the means for individualized exercise prescription.

Sex Differences In Microvascular Function In Pre-pubertal Children

There is little research examining the effect of sex on skin blood flow (SkBF) in adults, and less in children. Sex-related differences in SkBF may help explain known thermoregulatory differences between males and females. PURPOSE: To determine whether there are sex-related differences in the SkBF response to exercise, local heating, and acetylcholine (ACh). Additionally, the role of nitric oxide (NO) was examined. METHODS: Laser-Doppler flowmetry was used to assess forearm SkBF. Responses to exercise (30 min cycling, 60%V˙O2max), local heating (44°C), and ACh iontophoresis were assessed in 15 pre-pubertal boys (age=10±1y, VO2max=1.66±0.25 l/min) and 10 girls (age=10±1y, VO2max=1.58±0.35 l/min), with and without NO synthase inhibition, using L-NAME iontophoresis. Three-way (group, time, treatment) repeated measures ANOVA was used to examine sex-related differences in the SkBF response during exercise and in the SkBF-ACh dose response. A two-way (group, treatment) repeated measures ANOVA was used to examine local heathing-induced increase in SkBF. RESULTS: Exercise-induced SkBF was greater in boys compared with girls (654±355 and 316±182% of baseline, respectively, p=<.0001). L-NAME blunted the SkBF response more in boys than in girls (group-by-treatment interaction, p=.004). Local heating-induced SkBF was not significantly different between boys and girls (1705±739% and 1488±600%, respectively, p=.35), with no effect of L-NAME. The maximal ACh-induced SkBF was similar in boys and girls (650±420% and 612±411%, respectively). L-NAME similarly blunted the SkBF response in boys and girls (group-by-treatment interaction, p=.52). CONCLUSION: These findings demonstrate that while maximal SkBF and the vasodilatory response to ACh stimulation are similar in boys and girls, boys display a greater increase in SkBF during exercise of similar intensity. Further, the role of NO in the SkBF response appears greater in boys than girls only during exercise. Since absolute and relative exercise intensity was similar in the two groups, it is suggested that sex-related factors (e.g., hormones) may interact with the exercise response or with other vasodilators, resulting in different SkBF response.

Exercise Duration Affects Maximal Fat Oxidation In Post- Menopausal Women: Implications For Exercise Prescription

The relative exercise intensity at maximal fat oxidation (FATmax, %VO2max) is used for exercise prescription for weight loss and metabolic health. In young men, FATmax is affected by exercise duration, with more prolonged testing protocols leading to higher values. PURPOSE: Since no data exist on post-menopausal women, we determined the effect of exercise duration on FATmax in this population. METHOD: 18 non-obese women (54±4 years; 4±3 years from menopause; 22±3 BMI) performed on a cycle ergometer a ramp test and 30-min steady-state trials at 40, 50, 60, 70 and 80% of the pre-determined VO2max. Based on VO2 and respiratory exchange ratio we calculated and compared (2-way RM ANOVA) absolute fat oxidation (FO, g-1·min-1) across intensities and duration. We compared FATmax derived from ramp (rFATmax), 5 (5FATmax) and 30-min data (30FATmax) (1-way RM ANOVA). We estimated FATmax using exercise duration (1, 5 and 30 min) and rFATmax as explanatory variables. RESULTS: FO was significantly affected by exercise duration, intensity and their interaction (for all p<0.001). Any exercise between 40 and 70% %VO2max, > 30 min, lead to an identical MFO (overall 0.21±0.09 g-1·min-1). 30FATmax occurred at a significantly higher %VO2max (57±10%) than rFATmax and 5FATmax (44±6 and 49±9%, not different). FATmax can be predicted from the linear combination of exercise duration (p<0.001) and rFATmax (p=0.01) as independent explanatory variables (r=0.69, SEE=8.8%). CONCLUSIONS: In post-menopausal women exercises at 40-80%VO2max of longer durations are associated with higher FATmax compared to ramp or short, steady-state sessions. Moreover, any intensity greater than rFATmax will maximize fat oxidation for exercises > 30 min. Finally, the intensity that maximizes fat oxidation can be predicted by exercise duration and rFATmax. This approach offers a valid approach for individualized exercise intensity prescription for weight loss and metabolic health in postmenopausal women.

Validity Of The Session Rpe For Detecting Accumulated Fatigue

Studies have shown that the ratio of blood lactate concentration to Rating of Perceived Exertion (HLa/RPE) and session RPE (sRPE) may be considered useful to detect overreaching and accumulated fatigue. However, no study has investigated their relationship. PURPOSE: To examine the relationship between HLa/RPE and sRPE during a period of intensified training. METHODS: Twelve young adults performed incremental exercise to assess their max power output (MPO). They performed 30 and 60-min interval workouts on a cycle ergometer over a 2-week period. Each session started with a 5-min warm-up at 25% MPO followed by 5-min at 50% MPO, 2-min at 25% MPO, 5-min at 75% MPO, 2-min at 25% MPO, 2-min at 100% MPO, 2-min at 25% MPO and 7-min at 50% MPO, which finished the 30-min session. During the first week, 4 sessions consisting of 30-min on Monday, Tuesday, Wednesday and a 60-min (30-min session back to back) on Thursday, were organized. After 3 days off, the second week consisted of 3 consecutive 60-min sessions (Monday to Wednesday) with the last day (Thursday) being of 30-min. HLa and RPE were measured at the end of each stage of the interval training, and HLa/RPE computed for each session. sRPE was obtained after the sessions. Non-linear regression analysis was used to assess the relationship between HLa/RPE and sRPE. RESULTS: A very large negative relationship (r= -0.70, Root-mean-squared error =0.59, p<0.0001) was found (Figure 1). CONCLUSIONS: The negative relationship supports the concept that sRPE is a sensitive tool that, in addition to information about relative exercise intensity, might provide further information on accumulated fatigue. Coaches and exercise scientists without access to HLa measurment may gain insight into accumulated fatigue during periods of increased training by using sRPE.

The Separate And Combined Effects Of Acute Simulated Altitude And High Ambient Temperature On Cycling Time Trial Performance

Simulated altitude and high ambient temperature independently compromise endurance performance, although there is limited evidence on the combined exposure to both stressors. In addition, the effect of corresponding underlying key mechanisms has yet to be quantified. PURPOSE: To investigate the separate and combined effects of acute simulated altitude and high ambient temperature on time trial (TT) performance, VO2max, the ventilatory threshold (VT) and gross efficiency (GE). METHODS: Ten trained male cyclists performed 4 maximal incremental exercise tests (GXT) and GE-tests, both at sea-level (0 m; 20.93% O2) and simulated altitude (2000 m; 16.3% O2) in high environmental temperature (36.00 ± 1.4°C, 42.58 ± 0.8% RH) and temperate conditions (16.00 ± 0.32°C, 40.20 ± 1.2% RH). The GXT included 3 min at 100 W, followed by 25 W·min-1 until volitional fatigue. GE was determined at 50% of the power attained at VO2max in relative conditions, prior to and following 4000m TT performances. RESULTS: Although average PO was significantly reduced during TT performance at simulated altitude (31 ± 18 W, p<.001, n2p=.795) and high ambient temperature (9 ± 16 W, p=.007, n2p=.570), no significant interaction was found (p=.137). At simulated altitude, VO2max (3.77 ± 2.1 ml·kg-1·min-1, p<.001, n2p=.925), VT (3.39 ± 2.9 ml·kg-1·min-1, p<.001, n2p=.795) and GE (0.72 ± 0.97%, p=.021, n2p=0.555) were significantly reduced compared to sea level. However, VO2max (3.33 ± 3.1 ml·kg-1·min-1, p=.005, n2p=.608) and VT (2.05 ± 3.1 ml·kg-1·min-1, p=.021, n2p=.462) were significantly increased at high ambient temperature, although no effect on GE (p=0.240) was found. CONCLUSION: The reduction in TT performance at acute simulated altitude is associated with a decline in VO2max, VT and GE, likely because a lower SpO2. VO2max and VT are significantly higher at acute high ambient temperature, likely because the metabolic cost of physiological heat stress increases relative exercise intensity at similar absolute PO. GE was unaffected by acute high ambient temperature, likely because heat exposure during the GE-test was too short to increase Tcore. VO2max, VT and GE were not compromised during combined exposure, which corresponds with the absence of a significant interaction effect in endurance performance.

Perspectives on Exercise Intensity, Volume and Energy Expenditure in Habitual Cycle Commuting.

Background: Knowledge about exercise intensity and energy expenditure combined with trip frequency and duration is necessary for interpreting the character and potential influencing capacity of habitual cycle commuting on e.g., health outcomes. It needs to be investigated with validated methods, which is the purpose of this study.Methods: Ten male and 10 female middle-aged habitual commuter cyclists were studied at rest and with maximal exercise tests on a cycle ergometer and a treadmill in the laboratory. During their normal commute in the Stockholm County, Sweden, their oxygen uptake, heart rate, energy expenditure, ventilation, blood lactate, rated perceived exertion, number of stops, durations, route distances and cycling velocities were monitored with validated methods. The frequency of trips was self-reported.Results: The relative exercise intensity was 65% of maximal oxygen uptake, and the energy expenditure was 0.46 kcal per km and kg body weight for both sexes. Sex differences in MET-values (men, 8.7; women 7.4) mirrored higher levels of cycling speed (20%), body weight (29%), oxygen uptake (54%) and ventilation (51%) in men compared to women. The number of METhours per week during peak cycling season averaged 40 for the men and 28 for the women. It corresponded to a total energy expenditure of about 3,500 and 1,880 kcal for men and women, respectively. The number of trips per year was about 370, and the annual distance cycled was on average 3,500 km for men and 2,300 for women.Conclusion: Cycle commuting is characterized by equal relative aerobic intensity levels and energy requirements for a given distance cycled by men and women. Based on an overall evaluation, it represents a lower range within the vigorous intensity category. The combined levels of oxygen uptake, durations and trip frequencies lead to high levels of METhours and energy expenditure in both men and women during both peak cycling season as well as over the year. Overall, the study presents a novel basis for interpreting cycle commuting in relation to various health outcomes.

Inducible deletion of skeletal muscle AMPKα reveals that AMPK is required for nucleotide balance but dispensable for muscle glucose uptake and fat oxidation during exercise

ObjectiveEvidence for AMP-activated protein kinase (AMPK)-mediated regulation of skeletal muscle metabolism during exercise is mainly based on transgenic mouse models with chronic (lifelong) disruption of AMPK function. Findings based on such models are potentially biased by secondary effects related to a chronic lack of AMPK function. To study the direct effect(s) of AMPK on muscle metabolism during exercise, we generated a new mouse model with inducible muscle-specific deletion of AMPKα catalytic subunits in adult mice. MethodsTamoxifen-inducible and muscle-specific AMPKα1/α2 double KO mice (AMPKα imdKO) were generated by using the Cre/loxP system, with the Cre under the control of the human skeletal muscle actin (HSA) promoter. ResultsDuring treadmill running at the same relative exercise intensity, AMPKα imdKO mice showed greater depletion of muscle ATP, which was associated with accumulation of the deamination product IMP. Muscle-specific deletion of AMPKα in adult mice promptly reduced maximal running speed and muscle glycogen content and was associated with reduced expression of UGP2, a key component of the glycogen synthesis pathway. Muscle mitochondrial respiration, whole-body substrate utilization, and muscle glucose uptake and fatty acid (FA) oxidation during muscle contractile activity remained unaffected by muscle-specific deletion of AMPKα subunits in adult mice. ConclusionsInducible deletion of AMPKα subunits in adult mice reveals that AMPK is required for maintaining muscle ATP levels and nucleotide balance during exercise but is dispensable for regulating muscle glucose uptake, FA oxidation, and substrate utilization during exercise.

Intra-abdominal Pressure and Pelvic Floor Health: Should We Be Thinking About This Relationship Differently?

Intra-abdominal pressure (IAP) increases during physical activity. Activities with high IAP are often restricted for women because of potential pelvic floor overloading. Researchers categorize high IAP activities using absolute values (in centimeters of water). Although essential for descriptive purposes, absolute IAP may not be ideal for individualized exercise recommendations. For oxygen consumption, a well-established measure of fitness, exercise scientists use a percentage of the maximal value observed during exercise to create relative exercise intensity prescriptions for an individual. Relative exercise intensity correlates inversely to the maximal value observed. We explore whether this approach and response pattern extend to IAP observed during exercise. Fifty-five women completed 16 exercises while wearing a vaginal sensor to measure IAP. The highest mean IAP occurred during seated Valsalva/strain (IAPSTRAIN). We calculated relative IAP (in percent) for each participant by dividing the maximal IAP during each exercise by IAPSTRAIN. We examined relationships between relative IAP and IAPSTRAIN for each activity using Pearson r correlations. Mean age was 30.4 ± 9.4 years, and body mass index was 22.4 ± 2.6 kg/m. For most women, IAP was greater during strain than during exercises. Relative IAPs negatively correlated with IAPSTRAIN. Excluding one exercise because of small sample sizes, r for all others ranged from -0.35 to -0.80, all statistically significant. The relative IAP responses to many exercises exhibit an inverse relationship to the highest IAP values during strain, consistent with other variables measured during exercise. Relative IAP may provide an alternative to absolute IAP in understanding IAP's effect on pelvic floor health.