Journal of the International Society of Sports Nutrition最新文献

Background: The interactive effect of mental fatigue and caffeine consumption on sport performance is not clear. This study aimed to investigate the impact of mental fatigue and caffeine gum consumption on power and skill performance in recreationally trained male basketball players.

Methods: A randomized, double-blind, crossover design was used, with twenty male participants (age: 16.7 ± 0.86 years, body mass: 79.6 ± 8.2 kg, height: 183.2 ± 8.6 cm, training experience ≥ 3 years). Participants completed four testing sessions under the following conditions: (1) no mental fatigue with placebo gum, (2) mental fatigue with placebo gum, (3) no mental fatigue with caffeine gum, and (4) mental fatigue with caffeine gum. The sessions were separated by one week. Mental fatigue was induced through a 30-minute Stroop task, and caffeine gum (50 mg of caffeine per piece) was administered 15 minutes before performance testing. Power and skill performance were assessed via vertical jump height, V-CUT dribbling test, medicine ball throw, and stationary two-point shooting, with three attempts per test.

Results: Mental fatigue significantly increased time to react for congruent name and color (Z = 3.9, p < 0.001) and incongruent name and color (Z = 3.9, p < 0.001), as well as perceived fatigue (Z = 3.9, p < 0.001) after the Stroop task. Performance analysis revealed a significant main effect of condition on vertical jump height (F = 2.9, p = 0.04) and V-CUT dribbling performance (F = 4.4, p = 0.007), but not on medicine ball throw, change of direction test, or stationary two-point shooting (p > 0.05). Mental fatigue (mental fatigue with placebo gum) significantly impaired vertical jump height (p = 0.008) and V-CUT dribbling performance (p = 0.049) compared to the no mental fatigue with placebo gum condition. No significant differences were found between other condition pairs for these performance measures.

Conclusion: Mental fatigue negatively affects power and skill performance in basketball players, while caffeine gum consumption may offer a potential strategy to mitigate these effects. While caffeine gum attenuated some performance declines in the mental fatigue with caffeine gum condition compared to mental fatigue with placebo gum, these differences were not statistically significant. Future research should explore optimal caffeine doses and additional performance variables.

Background: This study aimed to compare the Athlete Diet Index (ADI) and body composition between professional and nonprofessional athletes to better understand how differences in training and nutrition impact athletic performance and health.

Method: A comparative cross-sectional design was used to analyze 183 athletes (99 professional, 84 nonprofessional) from various sports disciplines in Tehran. Data were collected on body composition parameters, including fat mass (FM) and fat free mass (FM) using bioelectrical impedance analysis (BIA) and the ADI, a validated tool for assessing diet quality.

Results: The results revealed that professional athletes had significantly lower FM percentages (16.2% ± 7.1%) and higher FFM percentages (80.8% ± 6.8%) compared to their nonprofessional counterparts (FM 18.8% ± 9.9%, FFM 78.0% ± 9.6%). Additionally, professional athletes exhibited higher ADI scores, indicating better adherence to sports nutrition guidelines.

Conclusions: These findings highlight the benefits of structured training and personalized nutrition in achieving favorable body composition. This study underscores the importance of personalized nutrition strategies for optimizing athletic health and performance, particularly for nonprofessional athletes who may not have access to professional dietary guidance. Further research is needed to explore the long-term effects of dietary and training interventions on body composition and athletic performance across various athlete populations.

Purpose: Limited data exists that compare pre-sleep versus post-exercise protein intake during resistance exercise training (RET) in older adults. This study examined whether 40 g of protein consumed post-exercise (PRP) or pre-sleep (PSP) enhances muscle thickness (MT) and strength compared to RET alone (RETO) in older men.

Methods: Thirty untrained older men (65.7 ± 4.0 yrs) completed 12 weeks of supervised RET (2×/week) and were randomized to PRP (n = 9), PSP (n = 11), or RETO (n = 10). MT of the vastus lateralis (VL), rectus femoris (RF), and vastus intermedius (VI) and 1-repetition maximum (1-RM) for leg and chest press were assessed at weeks 0, 6, and 12.

Results: VL (0 to 12 weeks: + 0.16 cm, 95% C.I. [0.06, 0.25]), RF (0 to 12 weeks: + 0.13 cm, 95% C.I. [0.03, 0.23]), and VI MT (0 to 12 weeks: + 0.18 cm, 95% C.I. [0.05, 0.31]) and chest press (0 to 12 weeks: + 10.9 kg, 95% C.I. [5.50, 16.3]) and leg press (0 to 12 weeks: + 28.3 kg, 95% C.I. [19.63, 37.1]) 1-RM increased (p < 0.050) with no group differences.

Conclusion: Consuming 40 g of protein post-exercise or pre-sleep did not enhance RET-induced improvements in muscle thickness or strength in older adults with adequate baseline protein intake (≥1.0 g/kg/day). RET alone elicited significant gains, emphasizing that adherence to training and meeting daily protein requirements are more critical than timing strategies for untrained older adults. ClinicalTrials.gov identifier: NCT05922475, 06/23/2023, retrospectively registered.

Background: Although blood flow restriction (BFR) resistance training effectively enhances muscle strength, it increases fatigue susceptibility due to hypoxic stress. This study investigated whether combining caffeine - a common ergogenic aid - with BFR could provide additional training benefits.

Methods: Twenty-eight young adults completed a 4-week low-load resistance training program for wrist extensors, divided into two groups: BFR (n = 14) and BFR with caffeine (BFRC, n = 14). Both groups performed the same occluded training at 20% of maximal voluntary contraction (MVC), with the BFRC group consuming 6 mg·kg^{- 1} caffeine one hour prior. Pre- and posttests assessed MVC and force control during a task involving gradual force increase and release.

Results: The results demonstrated comparable training-related increases in MVC and precision of control of force in both groups (p > .05). However, only the BFRC group exhibited a significant training-related decline in the size of force fluctuations (p = .002) with enhanced complexity during force release (p = .036). Consistent with the characteristic changes in force fluctuations, the BFRC group exhibited smaller variability (p = .002) and a higher mean frequency (p = .023) of pooled motor unit discharges during force release.

Conclusions: While caffeine does not significantly enhance strength gains after four weeks of isometric BFR training in untrained individuals, it improves force release precision by globally reducing motor unit discharge variability.

Background: Recent advancements in Continuous Glucose Monitoring (CGM) technology provide a novel solution for monitoring dynamic glucose fluctuations during endurance exercise, enabling personalized carbohydrate refueling strategies. However, direct evidence demonstrating its superiority over traditional refueling guidelines has been lacking. This exploratory study compared a CGM-informed protocol with a traditional interval-based (TRAD) carbohydrate refueling protocol on endurance exercise responses.

Methods: Twelve healthy, non-diabetic males (age = 32.3 ± 6.3 years) participated in two trials involving 75 minutes of continuous cycling at 50% peak power output, with the two carbohydrate refueling protocols implemented in a randomized, crossover order. In the TRAD protocol, participants received standard carbohydrate solutions at regular 15-min intervals, while replenishment timing in the CGM-informed protocol was guided by real-time glucose trends, particularly during declines.

Results: No significant differences were observed in heart rate, blood lactate, or perceived exertion between conditions (all p > 0.05). However, CGM-informed protocol displayed a lower coefficient of variation of glucose levels (8.82 ± 4.68%) than the TRAD protocol (11.95 ± 3.41%, Cohen's d  = 0.76, p = 0.013), indicating a steadier blood glucose trend. The mean 75-minute interstitial glucose total area under the curve was significantly lower for the CGM-informed protocol (423.4 ± 39.1 mmol·min·L-1), compared to the TRAD protocol (448.6 ± 38.2 mmol·min·L-1, Cohen's d = 0.65, p = 0.008).

Conclusion: While the CGM-informed protocol did not demonstrate beneficial effects on physiological responses over the TRAD protocol, it may aid in stabilizing glucose levels during prolonged endurance exercise. Further research is warranted to explore the applications of personalized carbohydrate refueling strategy based on CGM technology on athletic performance across various exercise protocols.   .

Background: Effective nutritional support is essential for maintaining good performance during exercise. Taste and olfaction are key senses for food intake, and understanding how their sensitivities change during exercise is important for effective nutritional support. However, the effects of exercise on taste and odor sensitivities remain unclear. This study aimed to investigate changes in taste and odor sensitivities during repeated endurance exercise using a bicycle ergometer.

Methods: A total of 20 women (mean age; 21.6 ± 0.2 years) participated in the study, completing four 60-minute segments, each comprising 50 minutes of bicycle ergometer exercise at an exercise intensity of 60% heart rate reserve and a 10-minute sensory test. The sensory tests were conducted five times in total: after each exercise segment and once before exercise as a control. Four concentrations (×0.5, ×0.75, ×1, and × 1.25) of a commercially available isotonic beverage were used as taste samples, and the subjects evaluated the taste intensity, preference, and odor intensity. Four types of food odorants were used as odor samples, and the subjects rated their preference. The subjects also reported their perceived fatigue levels during the taste and odor tests. Fatigue levels and taste intensity were rated using a 100-mm visual analogue scale, and taste and odor preferences and odor intensity were evaluated using a scoring method.

Results: The degree of physical fatigue significantly increased with each successive bicycle exercise segment. The taste intensity and preference for beverages with higher concentrations increased as the number of exercise segments increased, showing a significant increase in taste intensity for the × 1.25 solution in the final segment compared with before the tests. On the other hand, no significant effect was observed on the perceived odor intensity of the isotonic beverages. Similarly, there was no significant effect on the preference for odor samples due to repeated exercise.

Conclusions: These results suggest that taste sensitivity may change with prolonged exercise. Additionally, since odor intensity and preference were not significantly affected by repeated exercise, odor sensitivity may be less impacted by exercise than taste sensitivity.