Novos resumos em Ciências do Esporte: HIIT, Suplementação e Força. Direto do European Journal of Applied Physiology

Effect of sprint interval training on circulatory function during exercise in sedentary, overweight/obese women

Jennifer L. TrilkArpit SinghalKevin A. Bigelman and Kirk J. Cureton

Very high-intensity, low-volume, sprint interval training (SIT) increases muscle oxidative capacity and may increase maximal oxygen uptake (VO2max), but whether circulatory function is improved, and whether SIT is feasible in overweight/obese women is unknown. To examine the effects of SIT on VO2max and circulatory function in sedentary, overweight/obese women. Twenty-eight women with BMI > 25 were randomly assigned to SIT or control (CON) groups. One week before pre-testing, subjects were familarized to VO2max testing and the workload that elicited 50% VO2max was calculated. Pre- and post-intervention, circulatory function was measured at 50% of the pre-intervention VO2max, and a GXT was performed to determine VO2max. During the intervention, SIT training was given for 3 days/week for 4 weeks. Training consisted of 4–7, 30-s sprints on a stationary cycle (5% body mass as resistance) with 4 min active recovery between sprints. CON maintained baseline physical activity. Post-intervention, heart rate (HR) was significantly lower and stroke volume (SV) significantly higher in SIT (−8.1 and 11.4%, respectively; P < 0.05) during cycling at 50% VO2max; changes in CON were not significant (3 and −4%, respectively). Changes in cardiac output (Q) and arteriovenous oxygen content difference [(a − v)O2 diff] were not significantly different for SIT or CON. The increase in VO2max by SIT was significantly greater than by CON (12 vs. −1%). Changes by SIT and CON in HRmax (−1 vs. −1%) were not significantly different. Four weeks of SIT improve circulatory function during submaximal exercise and increases VO2max in sedentary, overweight/obese women.

The effects of 6-week-decoupled bi-pedal cycling on submaximal and high intensity performance in competitive cyclists and triathletes

Billy SperlichStefan ZelleHeinz KleinöderMatthias LochmannChristoph ZinnerHans-Christer Holmbergand Joachim Mester

 

Aim of this work was to examine the effects of decoupled two-legged cycling on (1) submaximal and maximal oxygen uptake, (2) power output at 4 mmol L−1 blood lactate concentration, (3) mean and peak power output during high intensity cycling (30 s sprint) and (4) isometric and dynamic force production of the knee extensor and flexor muscles. 18 highly trained male competitive male cyclists and triathletes (age 24 ± 3 years; body height 179 ± 11 cm; body mass 78 ± 8 kg; peak oxygen uptake 5,070 ± 680 mL min−1) were equally randomized to exercise on a stationary cycle equipped either with decoupled or with traditional crank system. The intervention involved 1 h training sessions, 5 times per week for 6 weeks at a heart rate corresponding to 70% of VO2peakVO2 at 100, 140, 180, 220 and 260 and power output at 4 mmol L−1 blood lactate were determined during an incremental test. VO2peak was recorded during a ramp protocol. Mean and peak power output were assessed during a 30 s cycle sprint. The maximal voluntary isometric strength of the quadriceps and biceps femoris muscles was obtained using a training machine equipped with a force sensor. No differences were observed between the groups for changes in any variable (P = 0.15–0.90; effect size = 0.00–0.30). Our results demonstrate that a 6 week (30 sessions) training block using decoupled crank systems does not result in changes in any physiological or performance variables in highly trained competitive cyclists.

Salivary estradiol, interleukin-6 production, and the relationship to substrate metabolism during exercise in females

Stephen J. IvesMark BlegenMary A. CoughlinJan RedmondTracey Matthews and Vincent Paolone

 

Estradiol (E2) has been documented to have anti-inflammatory effects on the immune system. Interleukin-6 (IL-6), is classified as a “myokine”, and has known metabolic consequences. Thus, the purpose of this study was to determine the effects of menstrual phase and exercise on the interaction of E2 and IL-6, and the role of IL-6 in substrate metabolism. Ten female subjects completed three separate testing sessions: baseline evaluation, and 1 h of treadmill exercise at 65% of peak VO2 during both the midfollicular (MF) and midluteal (ML) menstrual phases. Saliva was collected prior to, during, and post-exercise for determination of E2 and IL-6. Expired gases and an additional saliva sample were collected 30 min post-exercise. No significant differences were observed in any of the measured variables across menstrual phase. Exercise resulted in an acute rise in estradiol and IL-6; however, E2 was not related to IL-6 at baseline or in response to exercise. IL-6 remained elevated at the end of exercise and was found to be related to energy expenditure from fat, and to total energy expenditure at 60 min, and 30 min post-exercise. No relationships were found between the anti-inflammatory estrogen E2 and the cytokine IL-6. However, relationships were found between IL-6 and indices of substrate metabolism. Based on the data from the current research, IL-6 likely plays a metabolic role in healthy individuals during exercise when released from the muscle as a result of reduced energy availability, acting as a “myokine”, in comparison to inflammation-induced IL-6 release.

Effect of caffeine ingestion after creatine supplementation on intermittent high-intensity sprint performance

Chia-Lun LeeJung-Charng Lin and Ching-Feng Cheng

 

The aim of this study was to investigate the effects of acute caffeine ingestion on intermittent high-intensity sprint performance after 5 days of creatine loading. After completing a control trial (no ergogenic aids, CON), twelve physically active men were administered in a double-blind, randomized crossover protocol to receive CRE + PLA (0.3 g kg−1 day−1 of creatine for 5 days then followed by 6 mg kg−1of placebo) and CRE + CAF (0.3 g kg−1 day−1 of creatine for 5 days and followed by 6 mg kg−1 of caffeine), after which they performed a repeated sprint test. Each test consisted of six 10-s intermittent high-intensity sprints on a cycling ergometer, with 60-s rest intervals between sprints. Mean power, peak power, rating of perceived exertion (RPE), and heart rates were measured during the test. Blood samples for lactate, glucose, and catecholamine concentrations were drawn at specified intervals. The mean and peak power observed in the CRE + CAF were significantly higher than those found in the CON during Sprints 1 and 3; and the CRE + CAF showed significantly higher mean and peak power than that in the CRE + PLA during Sprints 1 and 2. The mean and peak power during Sprint 3 in the CRE + PLA was significantly greater than that in the CON. Heart rates, plasma lactate, and glucose increased significantly with CRE + CAF during most sprints. No significant differences were observed in the RPE among the three trials. The present study determined that caffeine ingestion after creatine supplements augmented intermittent high-intensity sprint performance.

Kinetics of skeletal muscle O2 delivery and utilization at the onset of heavy-intensity exercise in pulmonary arterial hypertension

Priscila B. BarbosaEloara M. V. FerreiraJaquelina S. O. ArakakiLuciana S. TakaraJuliana MouraRúbia B. NascimentoLuiz E. Nery and J. Alberto Neder

 

Impaired O2 delivery relative to O2 demands at the onset of exercise might influence the response profile of muscle fractional O2 extraction (≅Δ[deoxy-Hb/Mb] by near-infrared spectroscopy) either by accelerating its rate of increase or creating an “overshoot” (OS) in patients with pulmonary arterial hypertension (PAH). We therefore assessed the kinetics of O2 uptake VO2  Δ[deoxy-Hb/Mb] in the vastus lateralis, and heart rate (HR) at the onset of heavy-intensity exercise in 14 females with PAH (connective tissue disease, IPAH, portal hypertension, and acquired immunodeficiency syndrome) and 11 age- and gender-matched controls. Patients had slower VO2 and HR dynamics than controls (τVO2 = 62.7 ± 15.2 s vs. 41.0 ± 13.8 s and t 1/2-HR = 61.3 ± 16.6 s vs. 43.4 ± 8.8 s, respectively; p < 0.01). No study participant had a significant reduction in oxyhemoglobin saturation. In OS(−) subjects (6 patients and 7 controls), the kinetics of Δ[deoxy-Hb/Mb] relative to VO2 were faster in patients (p = 0.05). Larger area under the OS and slower kinetics (MRT) of the “downward” component indicated greater O2 delivery-to-utilization mismatch in OS(+) patients versus OS(+) controls (477.4 ± 330.0 vs. 78.1 ± 65.6 a.u. and 74.6 ± 18.8 vs. 46.0 ± 17.0 s, respectively; p < 0.05). Resting pulmonary vascular resistance was higher in OS(+) than OS(−) patients (23.1 ± 12.0 vs. 10.7 ± 4.0 Woods, respectively; p < 0.05). We conclude that microvascular O2 delivery-to-utilization inequalities slowed the rate of adaptation of aerobic metabolism at the start of heavy-intensity exercise in women with PAH.
Impaired O2 delivery relative to O2 demands at the onset of exercise might influence the response profile of muscle fractional O2 extraction (≅Δ[deoxy-Hb/Mb] by near-infrared spectroscopy) either by accelerating its rate of increase or creating an “overshoot” (OS) in patients with pulmonary arterial hypertension (PAH). We therefore assessed the kinetics of O2 uptake VO2  Δ[deoxy-Hb/Mb] in the vastus lateralis, and heart rate (HR) at the onset of heavy-intensity exercise in 14 females with PAH (connective tissue disease, IPAH, portal hypertension, and acquired immunodeficiency syndrome) and 11 age- and gender-matched controls. Patients had slower VO2 and HR dynamics than controls (τVO2 = 62.7 ± 15.2 s vs. 41.0 ± 13.8 s and t 1/2-HR = 61.3 ± 16.6 s vs. 43.4 ± 8.8 s, respectively; p < 0.01). No study participant had a significant reduction in oxyhemoglobin saturation. In OS(−) subjects (6 patients and 7 controls), the kinetics of Δ[deoxy-Hb/Mb] relative to VO2 were faster in patients (p = 0.05). Larger area under the OS and slower kinetics (MRT) of the “downward” component indicated greater O2 delivery-to-utilization mismatch in OS(+) patients versus OS(+) controls (477.4 ± 330.0 vs. 78.1 ± 65.6 a.u. and 74.6 ± 18.8 vs. 46.0 ± 17.0 s, respectively; p < 0.05). Resting pulmonary vascular resistance was higher in OS(+) than OS(−) patients (23.1 ± 12.0 vs. 10.7 ± 4.0 Woods, respectively; p < 0.05). We conclude that microvascular O2 delivery-to-utilization inequalities slowed the rate of adaptation of aerobic metabolism at the start of heavy-intensity exercise in women with PAH.
Impaired O2 delivery relative to O2 demands at the onset of exercise might influence the response profile of muscle fractional O2 extraction (≅Δ[deoxy-Hb/Mb] by near-infrared spectroscopy) either by accelerating its rate of increase or creating an “overshoot” (OS) in patients with pulmonary arterial hypertension (PAH). We therefore assessed the kinetics of O2 uptake VO2  Δ[deoxy-Hb/Mb] in the vastus lateralis, and heart rate (HR) at the onset of heavy-intensity exercise in 14 females with PAH (connective tissue disease, IPAH, portal hypertension, and acquired immunodeficiency syndrome) and 11 age- and gender-matched controls. Patients had slower VO2 and HR dynamics than controls (τVO2 = 62.7 ± 15.2 s vs. 41.0 ± 13.8 s and t 1/2-HR = 61.3 ± 16.6 s vs. 43.4 ± 8.8 s, respectively; p < 0.01). No study participant had a significant reduction in oxyhemoglobin saturation. In OS(−) subjects (6 patients and 7 controls), the kinetics of Δ[deoxy-Hb/Mb] relative to VO2 were faster in patients (p = 0.05). Larger area under the OS and slower kinetics (MRT) of the “downward” component indicated greater O2 delivery-to-utilization mismatch in OS(+) patients versus OS(+) controls (477.4 ± 330.0 vs. 78.1 ± 65.6 a.u. and 74.6 ± 18.8 vs. 46.0 ± 17.0 s, respectively; p < 0.05). Resting pulmonary vascular resistance was higher in OS(+) than OS(−) patients (23.1 ± 12.0 vs. 10.7 ± 4.0 Woods, respectively; p < 0.05). We conclude that microvascular O2 delivery-to-utilization inequalities slowed the rate of adaptation of aerobic metabolism at the start of heavy-intensity exercise in women with PAH.

Enhancement of jump performance after a 5-RM squat is associated with postactivation potentiation

Cameron J. Mitchell and Digby G. Sale

 

Weight lifting exercise may induce postactivation potentiation (PAP), thereby enhancing performance of a subsequent biomechanically similar “explosive” movement. However, it has not been shown that weight lifting induces PAP, indicated as potentiation of muscle twitch force. Therefore, the present study tested whether a five repetition maximum squat (5-RM squat) both induced PAP and increased the height of subsequently performed counter-movement jumps (CMJs). Eleven male athletes completed four laboratory sessions on separate days. Two sessions determined whether the 5-RM squat induced PAP: in one, a quadriceps maximal twitch was evoked immediately before and 8 min after a set of five CMJs (control); in the other, a twitch was evoked before a CMJ set, which was followed by a 4-min rest, a 5-RM squat, a 4-min rest, and a second twitch. Another two sessions tested the effect of the 5-RM squat on jump performance: in one session, two sets of five CMJs were performed with an 8-min rest between the sets (control); in the second, a 5-RM squat was performed 4 min after the first set of CMJs, and then after another 4 min the second set of CMJs was performed. Neither twitch torque nor CMJ height changed in the control sessions (P > 0.05). In contrast, interpolation of the 5-RM squat increased (P < 0.05) both twitch torque (49.5 ± 7.8 to 54.8 ± 11.9 N m; i.e., PAP = 10.7%) and CMJ height (48.1 ± 5.6 to 49.5 ± 5.9 cm; 2.9%). Since PAP was present at the time when CMJ height increased, it was concluded that PAP may have contributed to the increased CMJ height after a 5-RM squat.

 

 

 

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