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The Dose-Effects of Caffeine on Lower Body Maximal Strength, Muscular Endurance, and Rating of Perceived Exertion in Strength-Trained Females.
Jones, L, Johnstone, I, Day, C, Le Marquer, S, Hulton, AT
Nutrients. 2021;13(10)
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Caffeine is a common ingredient in tea, coffee, chocolate, soft drinks and multi-ingredient pre-workout supplements. It is believed to elicit an ergogenic effect that enhances athletic performance. However, only very few studies have examined the effect of caffeine on women who take contraceptive pills. The aim of this double-blind, randomised, counterbalanced, crossover trial was to investigate the ergogenic effect of pre-exercise caffeine supplementation on strength performance and muscular endurance in strength-trained females taking contraceptives. Fourteen women were randomised to consume doses of 3 and 6 mg·kg−1 body mass of caffeine supplement or placebo thirty minutes prior to the exercise. Caffeine supplementation at 3 and 6 mg·kg−1 body mass significantly improved muscular endurance and total strength. No significant difference was observed between the higher and lower doses of caffeine in improving performance, indicating that the lower dose can potentially provide the same benefit without the adverse effect of the higher dose. The low dose had a similar caffeine content to that of a large coffee latte from a coffee shop, suggesting beneficial effects could be achieved through coffee/latte consumption. Caution should be applied when extrapolating the findings for eumenorrheic females with different training statuses. Healthcare practitioners can, however, use the results of this study to understand the potential benefits of caffeine for strength-trained women using hormone contraception.
Abstract
Caffeine supplementation has shown to be an effective ergogenic aid enhancing athletic performance, although limited research within female populations exists. Therefore, the aim of the investigation was to assess the effect of pre-exercise caffeine supplementation on strength performance and muscular endurance in strength-trained females. In a double-blind, randomised, counterbalanced design, fourteen strength-trained females using hormonal contraception consumed either 3 or 6 mg·kg-1 BM of caffeine or placebo (PLA). Following supplementation, participants performed a one-repetition maximum (1RM) leg press and repetitions to failure (RF) at 60% of their 1RM. During the RF test, rating of perceived exertion (RPE) was recorded every five repetitions and total volume (TV) lifted was calculated. Repeated measures ANOVA revealed that RF (p = 0.010) and TV (p = 0.012) attained significance, with pairwise comparisons indicating a significant difference between 3 mg·kg-1 BM and placebo for RF (p = 0.014), with an effect size of 0.56, and for 6 mg·kg-1 BM (p = 0.036) compared to the placebo, with an effect size of 0.65. No further significance was observed for 1RM or for RPE, and no difference was observed between caffeine trials. Although no impact on lower body muscular strength was observed, doses of 3 and 6 mg·kg-1 BM of caffeine improved lower body muscular endurance in resistance-trained females, which may have a practical application for enhancing resistance training stimuli and improving competitive performance.
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Development and content validity of an instrument for assessing the motivation for weight loss in adolescents with overweight and obesity.
Silva, DFO, Souza, ALS, Pimentel, JB, Souza, TO, Araújo, EPDS, Sena-Evangelista, KCM, Arrais, RF, Lima, SCVC
PloS one. 2020;15(11):e0242680
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Reduction and control of body weight is an important measure in order to reduce health risks in adolescence and adulthood. The aim of this study was to develop and validate the content of an instrument to assess the motivation for weight loss in adolescents with overweight and obesity. This is a methodological study. The development and content validation of the instrument was conducted in five stages. There were three rounds of evaluation; in the first round the responses of 12 experts were included, in the second round the responses of 10 experts were included and in the final round the responses of four experts were included. Findings show that the content validity evaluation of the items by the panel of experts allowed the selection of the most practical items for adolescents. Additionally, the revisions made in the wording of the items provided a better standardization in the presentation of the items and a clearer language adapted to the age range of the target audience. Authors conclude that further psychometric testing is needed to determine reliability and construct validity of the instrument.
Abstract
OBJECTIVE To develop and validate the content of an instrument for assessing the motivation for weight loss in adolescents with overweight and obesity. METHODS The development and validation of the instrument were conducted in five stages, for which two systematic reviews were conducted. The first one, for the identification of questionnaires assessing the motivation for weight loss, included six studies and contributed to the selection of the domains for the instrument. The second one, conducted to identify the motivations for weight loss in adolescents with overweight and/or obesity, included six studies and contributed to the selection of 17 motivations included in the initial version of the instrument. The motivations most commonly identified were: having better health, improving my appearance, improving my self-esteem and avoiding bullying. The content validity was confirmed by a committee of 12 experts from the areas of nutrition, endocrinology, psychology, and physical education. Based on these evaluations, the content validity index was calculated. Only the items with a content validity index >0.80 for practical relevance were held in the instrument. RESULTS Five of the 17 motivations included in the initial version of the instrument were excluded because they had content validity index <0.80 for practical relevance. Of the 12 items held in the instrument, five were revised by experts in order to standardize wording and make the language more appropriate for adolescents. Experts categorized the items into the health, personal satisfaction, appearance and social domains. CONCLUSIONS This is the first instrument assessing the motivation for weight loss in adolescents with overweight and obesity in Brazil. The content validity evaluation by the panel of experts provided more practical relevance, as well as contributed to a better presentation of the items. Further psychometric testing is needed to determine reliability and construct validity of the instrument.
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Acceptability of a very-low-energy diet in Type 2 diabetes: patient experiences and behaviour regulation.
Rehackova, L, Araújo-Soares, V, Adamson, AJ, Steven, S, Taylor, R, Sniehotta, FF
Diabetic medicine : a journal of the British Diabetic Association. 2017;34(11):1554-1567
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Patients with type 2 diabetes can return to normal blood glucose levels through substantial weight loss. While many studies have addressed this, very few have assessed the effects of adherence to a very-low-energy diet (VLED) on patients’ quality of life. The aim of this study was to evaluate the experiences of adhering to VLED for patients in remission for type 2 diabetes. Fifteen participants were interviewed before and after the 8-week VLED intervention and narratives were analysed. This study identified common barriers, facilitators and strategies used by the participants. Overall, participants found adherence easier than anticipated, and found barriers to be offset by suggested behaviour-regulation strategies. Based on this study, the authors conclude dietary treatment for reversal of type 2 diabetes is acceptable and feasible in motivated patients, and suggest further controlled research be done to confirm the validity and applicability of these findings.
Abstract
AIMS: To evaluate the acceptability of an 8-week very-low-energy diet for remission of Type 2 diabetes, and to identify barriers and facilitators of adherence and behaviour-regulation strategies used by participants in the Counterbalance study. METHODS Eighteen of 30 participants in the Counterbalance study (ISRCTN88634530) took part in semi-structured interviews. Of these, 15 participants were interviewed before and after the 8-week very-low-energy diet intervention. Thematic analysis was used to analyse the narratives. RESULTS The prospect of diabetes remission, considerable weight loss, and long-term health improvement provided participants with substantial initial motivation. This motivation was sustained through the experience of rapid weight loss, improvements in blood glucose levels, social support and increased physical and psychological well-being. Overall, adherence to the very-low-energy diet for 8 weeks was perceived as much easier than anticipated, but required personal effort. Participants addressed challenges by removing food from the environment, planning, avoidance of tempting situations or places, and self-distraction. Weight loss and improvements in blood glucose levels lead to a sense of achievement and improvements in physical and psychological wellbeing. CONCLUSIONS Dietary treatment for reversal of Type 2 diabetes is acceptable and feasible in motivated participants, and the process is perceived as highly gratifying. Research outside of controlled trial settings is needed to gauge the generalisability of these findings.
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Postprandial Glucose Surges after Extremely Low Carbohydrate Diet in Healthy Adults.
Kanamori, K, Ihana-Sugiyama, N, Yamamoto-Honda, R, Nakamura, T, Sobe, C, Kamiya, S, Kishimoto, M, Kajio, H, Kawano, K, Noda, M
The Tohoku journal of experimental medicine. 2017;243(1):35-39
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Carbohydrate-restricted diets are prevalent not only in obese people but also in the general population to maintain appropriate body weight. The aim of the study was to investigate, through continuous glucose monitoring, whether carbohydrate restriction for one day in actual life could affect the subsequent blood glucose levels in healthy subjects. The study enrolled ten healthy volunteers (2 males and 8 females), who had normal haemoglobin A1c, with an age range between 20 years and 65 years. The participants wore a continuous glucose monitoring device and were given isoenergetic test meals for 4 consecutive days. Results show that after extreme restriction of carbohydrate, an influence on the blood glucose variability persisted for at least 24 hours in healthy subjects. The day after the low-carbohydrate/high-fat diet, the glucose fluctuation increased significantly when compared with the fluctuations on days after the ingestion of normal carbohydrate diet. Authors conclude that low carbohydrate/high-fat diets can induce increasing blood glucose fluctuations that last for at least all the following day and have adverse effects in daily life.
Abstract
Carbohydrate-restricted diets are prevalent not only in obese people but also in the general population to maintain appropriate body weight. Here, we report that extreme carbohydrate restriction for one day affects the subsequent blood glucose levels in healthy adults. Ten subjects (median age 30.5 years, BMI 21.1 kg/m2, and HbA1c 5.5%), wearing with a continuous glucose monitoring device, were given isoenergetic test meals for 4 consecutive days. On day 1, day 2 (D2), and day 4 (D4), they consumed normal-carbohydrate (63-66% carbohydrate) diet, while on day 3, they took low-carbohydrate/high-fat (5% carbohydrate) diet. The daily energy intake was 2,200 kcal for males and 1,700 kcal for females. On D2 and D4, we calculated the mean 24-hr blood glucose level (MEAN/24h) and its standard deviation (SD/24h), the area under the curve (AUC) for glucose over 140 mg/dL within 4 hours after each meal (AUC/4h/140), the mean amplitude of the glycemic excursions (MAGE), the incremental AUC of 24-hr blood glucose level above the mean plus one standard deviation (iAUC/MEAN+SD). Indexes for glucose fluctuation on D4 were significantly greater than those on D2 (SD/24h; p = 0.009, MAGE; p = 0.013, AUC/4h/140 after breakfast and dinner; p = 0.006 and 0.005, and iAUC/MEAN+SD; p = 0.007). The value of MEAN/24h and AUC/4h/140 after lunch on D4 were greater than those on D2, but those differences were not statistically significant. In conclusion, consumption of low-carbohydrate/high-fat diet appears to cause higher postprandial blood glucose on subsequent normal-carbohydrate diet particularly after breakfast and dinner in healthy adults.