This study compared changes in substrate metabolism with high intensity interval training (HIIT) in women of different ethnicities. Twelve Caucasian (C) and ten Hispanic women (H) (age = 24 ± 5 yr) ...who were inactive completed nine sessions of HIIT at 85 percent peak power output (%PPO). Pre-training, changes in fat oxidation (FOx) and carbohydrate oxidation (CHOOx) during progressive cycling were measured on two days to compute the minimum difference (MD). This test was repeated after the last training session. Between baseline tests, estimates of FOx and CHOOx were not different (
> 0.05) and were highly related (intraclass correlation coefficient equal to 0.72 to 0.88), although the coefficient of variation of maximal fat oxidation (MFO) was equal to 30%. Training significantly increased MFO (
= 0.03) in C (0.19 ± 0.06 g/min to 0.21 ± 0.06 g/min,
= 0.66) and H (0.16 ± 0.03 g/min to 0.19 ± 0.03 g/min,
= 1.3) that was similar (
= 0.92) between groups. There was a significant interaction for FOx (
= 0.003) as it was only increased in H versus C, although both groups exhibited reduced CHO oxidation (
= 0.002) with training. Use of MD revealed that only 3 of 22 women show meaningful increases in MFO (>0.08 g/min). The preliminary data reveals that a small dose of low-volume HIIT does not alter fat and CHO oxidation and there is little effect of ethnicity on the response to training.
Spinal cord injury (SCI) leads to loss of sensory and motor function below the level of injury leading to paralysis and limitations to locomotion. Therefore, persons with SCI face various challenges ...in engaging in regular physical activity, which leads to a reduction in physical fitness, increases in body fat mass, and reduced physical and mental health status. Moderate intensity continuous training (MICT) is recommended to enhance physical fitness and overall health status in this population, but it is not always effective in promoting these benefits. High intensity interval training (HIIT) has been promoted as an alternative to MICT in individuals with SCI due to its documented efficacy in healthy able-bodied individuals as well as those with chronic disease. However, the body of knowledge concerning its application in this population is limited and mostly composed of studies with small and homogeneous samples. The aim of this review was to summarize the existing literature regarding the efficacy of HIIT on changes in health- and fitness-related outcomes in this population, denote potential adverse responses to HIIT, describe how participants perceive this modality of exercise training, and identify the overall feasibility of interval training in persons with SCI.
Energy drinks are frequently consumed by athletes prior to competition to improve performance. This study examined the effect of Red Bull™ on repeated sprint performance in women athletes. Fifteen ...collegiate soccer players participated, with mean age, height, and body mass equal to 19.5 ± 1.1 year, 168.4 ± 5.8 cm, and 63.4 ± 6.1 kg, respectively. After performing a familiarization trial, subjects performed three sets of eight bouts of the modified
t
test after ingestion of 255 mL of placebo or Red Bull 1 h pre-exercise in a randomized, placebo-controlled crossover design. Throughout testing, sprint time, heart rate (HR), and rating of perceived exertion (RPE) were continuously obtained. Repeated measures analysis of variance was used to examine differences in variables between drink conditions. Across athletes,
t
test time ranged from 10.4 to 12.7 s. Mean sprint time was similar (
p
> 0.05) between Red Bull (11.31 ± 0.61 s) and placebo (11.35 ± 0.61 s). HR and RPE increased (
p
< 0.05) during the bouts, but there was no effect (
p
> 0.05) of Red Bull on either variable versus placebo. Findings indicate that 255 mL of Red Bull containing 1.3 mg/kg of caffeine and 1 g of taurine does not alter repeated sprint performance, RPE, or HR in women athletes versus placebo. One serving of this energy drink provides no ergogenic benefit for women athletes engaging in sprint-based exercise.
Abstract Caffeine has been reported to alter perceptions of exertion, muscle pain, and mood, yet the majority of existing data were obtained in resting volunteers or during steady-state exercise. The ...primary aim of this study was to examine the effects of caffeine on rating of perceived exertion (RPE) and perceptions of leg pain, arousal, and pleasure/displeasure during a simulated cycling time trial. Endurance-trained (n = 8, VO2 max = 57.5 ± 3.9 mL/kg/min) and active (n = 8, VO2 max = 46.5 ± 6.3 mL/kg/min) men initially completed two familiarization trials separated by at least 48 h. Over the next three trials, they completed a 10 km time trial preceded by ingestion of drinks containing caffeine (5 mg/kg ingested on 2 separate days) or placebo. Treatments were ingested using a single-blind, crossover design, and participants were deceived as to the content of all drinks. During exercise, RPE (6–20 scale), leg pain (0–10 scale), arousal (Felt Arousal Scale), and pleasure/displeasure (Feeling Scale) were recorded using various categorical scales. Repeated measures analysis of variance was used to assess differences in all variables across time and treatments, with fitness level used as a between-subjects variable. Pleasure/displeasure was altered (p < 0.05, partial eta-squared (η2 ) = 0.23) with caffeine compared to placebo, although leg pain, RPE, and arousal were similar (p > 0.05) across treatments. Caffeine increased (p < 0.05, η2 = 0.27) cycling performance by 0.3–2.0% versus placebo, with no effect (p > 0.05) of fitness level. Only in trained men; however, was there a significant caffeine-mediated improvement in cycling performance, which was consequent with diminished mood in trained and improved mood in active individuals.
Multiple studies corroborate the ergogenic properties of caffeine (CAF) for endurance performance, yet fewer investigations document the efficacy of acute caffeine intake for intense, short-term ...exercise. The aim of the study was to determine the ergogenic potential of caffeine during testing of muscular strength and endurance. Twenty-two resistance-trained men ingested CAF (6 mg/kg) or placebo (PL) 1 h pre-exercise in a randomized, double-blind crossover design. They refrained from caffeine intake and strenuous exercise 48 and 24 h, respectively, pre-visit. Initially, resting heart rate and blood pressure were obtained followed by one-repetition maximum (1-RM) testing on the barbell bench press and leg press. Upon determination of 1-RM, participants completed repetitions to failure at 60%1-RM. Heart rate, blood pressure, and rating of perceived exertion (RPE) were measured after the final repetition. Compared to PL, there was no effect (
P
> 0.05) of caffeine on muscular strength, as 1-RM bench press (116.4 ± 23.6 kg vs. 114.9 ± 22.8 kg) and leg press (410.6 ± 92.4 kg vs. 394.8 ± 95.4 kg) were similar. Total weight lifted during the 60% 1-RM trial was 11 and 12% higher for the bench press and leg press with caffeine compared to placebo, yet did not reach significance. RPE was similar at the end of resistance exercise with CAF vs. PL. Acute caffeine intake does not significantly alter muscular strength or endurance during intense bench press or leg press exercise, yet the practical importance of the increased muscular endurance remains to be explored.
Repeated measures within-subjects crossover study.
High intensity interval exercise (HIIE) elicits higher oxygen consumption (VO
) and heart rate (HR) versus moderate intensity continuous exercise ...(MICE) in men with spinal cord injury (SCI). No study has compared hemodynamic responses to HIIE versus MICE in SCI. In this study, we determined hemodynamic and cardiorespiratory responses to different bouts of arm cycling in men with SCI.
Human Performance Laboratory, San Diego, CA.
Five men (age and injury duration = 42.6 ± 16.1 yr and 9.9 ± 7.6 yr) with SCI participated in the study. VO
peak and peak power output were initially assessed. Subsequent visits included MICE, HIIE, sprint interval exercise (SIE), and a no-exercise control (CON). Energy expenditure was matched across modes and equal to 100 ± 10 kcal. During the bouts, cardiac output (CO), stroke volume (SV), HR, and VO
were measured.
Heart rate, SV, and CO increased in response to all exercise bouts and were higher during exercise versus CON. During HIIE and SIE, heart rate approached 90% of maximum, and stroke volume increased by 40% which was higher (
< 0.05) versus MICE and CON. In addition, exercise led to a two (MICE) to threefold increase in CO (HIIE and SIE) although it was not different from CON. VO
during SIE and HIIE was higher (
< 0.05) versus MICE.
Similar to results in non-disabled populations, HIIE and SIE elicit near-maximal values of SV and CO.
Implementing permissive dehydration (DEH) during short-term heat acclimation (HA) may accelerate adaptations to the heat. However, HA with DEH may augment risk for acute kidney injury (AKI). This ...study investigated the effect of HA with permissive DEH on time-trial performance and markers of AKI. Fourteen moderately trained men (age and VO
= 25 ± 0.5 yr and 51.6 ± 1.8 mL
kg
min
) were randomly assigned to DEH or euhydration (EUH). Time-trial performance and VO
were assessed in a temperate environment before and after 7 d of HA. Heat acclimation consisted of 90 min of cycling in an environmental chamber (40 °C, 35% RH). Neutrophil gelatinase-associated lipocalin (NGAL) and kidney injury molecule-1 (KIM-1) were assessed pre- and post-exercise on day 1 and day 7 of HA. Following HA, VO
did not change in either group (
= 0.099); however, time-trial performance significantly improved (3%,
< 0.01) with no difference between groups (
= 0.485). Compared to pre-exercise, NGAL was not significantly different following day 1 and 7 of HA (
= 0.113) with no difference between groups (
= 0.667). There was a significant increase in KIM-1 following day 1 and 7 of HA (
= 0.002) with no difference between groups (
= 0.307). Heat acclimation paired with permissive DEH does not amplify improvements in VO
or time-trial performance in a temperate environment versus EUH and does not increase markers of AKI.
This study examined changes in enjoyment, affective valence, and rating of perceived exertion (RPE) in obese women performing two regimes of high intensity interval training (HIIT) differing in ...structure and volume. Nineteen obese and inactive women (age and body mass index = 37.5 ± 10.5 yr and 39.0 ± 4.3 kg/m
2
) were randomized to 6 wk of traditional (TRAD, n = 10) or periodized interval training (PER, n = 9) which was performed on a cycle ergometer during which structure changed weekly. Two supervised sessions per week were performed in a lab, and one session per week was performed unsupervised. During every lab-based session, perceptual responses including enjoyment, affective valence, and RPE were acquired. Data showed a groupXtraining interaction for enjoyment (p = 0.02) which was lower by 10-25 units during PER versus TRAD. In addition, there was a groupXtimeXtraining interaction for RPE (p = 0.01). RPE did not change in response to TRAD yet varied during PER, with lower RPE values exhibited during brief supramaximal bouts (6.3 ± 0.9) compared to longer intervals (7.3 ± 1.2). Both regimes showed reductions in affective valence during training, with the lowest values equal to 1.5 ± 1.6 in TRAD and −0.2 ± 1.6 in PER. Compared to TRAD, more aversive responses were shown in PER throughout training by 0.4-2.0 units. Data show lower enjoyment and more aversive responses to higher-volume bouts of interval training, which suggests that shorter bouts may be perceived more favourably by obese women.
High intensity interval training is frequently implemented using the 4 × 4 protocol where four 4-min bouts are performed at heart rate (HR) between 85 and 95% HR max. This study identified the HR and ...power output response to the 4 × 4 protocol in 39 active men and women (age and VO2 max = 26.0 ± 6.1 years and 37.0 ± 5.4 mL/kg/min). Initially, participants completed incremental cycling to assess VO2 max, HR max, and peak power output (PPO). They subsequently completed the 4 × 4 protocol, during which HR and power output were monitored. Data showed that 12.9 ± 0.4 min of 16 min were spent between 85 and 95% HR max, with time spent significantly lower in interval 1 (2.7 ± 0.6 min) versus intervals 2–4 (3.4 ± 0.4 min, 3.4 ± 0.3 min, and 3.5 ± 0.3 min, d = 2.4–2.7). Power output was highest in interval 1 (75% PPO) and significantly declined in intervals 2–4 (63 to 54% PPO, d = 0.7–1.0). To enhance time spent between 85 and 95% HR max for persons with higher fitness, we recommend immediate allocation of supramaximal intensities in interval one.
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