High-Fat Ketogenic Diets and Physical Performance: A Systematic Review

Use of high-fat, ketogenic diets (KDs) to support physical performance has grown in popularity over recent years. While these diets enhance fat and reduce carbohydrate oxidation during exercise, the impact of a KD on physical performance remains controversial. The objective of this work was to assess the effect of KDs on physical performance compared with mixed macronutrient diets [control (CON)]. A systematic review of the literature was conducted using PubMed and Cochrane Library databases. Randomized and nonrandomized studies were included if participants were healthy (free of chronic disease), nonobese [BMI (kg/m2) <30], trained or untrained men or women consuming KD (<50 g carbohydrate/d or serum or whole-blood β-hydroxybutyrate >0.5 mmol/L) compared with CON (fat, 12-38% of total energy intake) diets for ≥14 d, followed by a physical performance test. Seventeen studies (10 parallel, 7 crossover) with 29 performance (13 endurance, 16 power or strength) outcomes were identified. Of the 13 endurance-type performance outcomes, 3 (1 time trial, 2 time-to-exhaustion) reported lower and 10 (4 time trials, 6 time-to-exhaustion) reported no difference in performance between the KD compared with CON. Of the 16 power or strength performance outcomes, 3 (1 power, 2 strength) reported lower, 11 (4 power, 7 strength) no difference, and 2 (power) enhanced performance in the KD compared with the CON. Risk of bias identified some concern of bias primarily due to studies allowing participants to self-select diet intervention groups and the inability to blind participants to the study intervention. Overall, the majority of null results across studies suggest that a KD does not have a positive or negative impact on physical performance compared with a CON diet. However, discordant results between studies may be due to multiple factors, such as the duration consuming study diets, training status, performance test, and sex differences, which will be discussed in this systematic review.

Effects of Rest Position on Morphology of the Vastus Lateralis and Its Relationship with Lower-Body Strength and Power

Ultrasonography of the lower body typically encompasses supine rest due to fluid shifts affecting tissue size and composition. However, vastus lateralis (VL) examination is completed in the lateral recumbent position, and this positional change may influence morphology and its ability to predict function. This study aimed to examine the effect of position on VL morphology and its relationship with lower-body performance. Cross-sectional area (CSA), muscle thickness (MT), pennation angle (PA), echo intensity (UnCorEI), subcutaneous adipose tissue thickness (SFT), and echo intensity corrected for SFT (CorEI) were assessed in 31 resistance-trained males (23.0 ± 2.1 yrs; 1.79 ± 0.08 m; 87.4 ± 11.7 kg) immediately after transitioning from standing to supine (IP), after 15 min of standing (ST), and after 15 min of rest in three recumbent positions: supine (SUP), dominant lateral recumbent (DLR), non-dominant lateral recumbent (NDLR). Participants also completed unilateral vertical jumps, isometric/isokinetic tests, and a one-repetition maximum leg press. CSA, MT, PA, and SFT were greater in ST compared to NDLR, DLR, and SUP (p < 0.05). CSA, UnCorEI, and CorEI were different between recumbent positions; however no differences were observed for MT, PA, and SFT. Different magnitudes of relationships were observed between muscle morphological characteristics measured after rest in different positions and performance variables. Muscle morphology in IP generally appears to be the best predictor of performance for most variables, although utilizing the NDLR and DLR positions may provide comparable results, whereas morphology measured in ST and SUP provide weaker relationships with physical performance. IP also requires less time and fewer requirements on the technician and subject, thus researchers should consider this positioning for VL examination.

Physical Performance in Elite Male and Female Team-Handball Players

PURPOSE

Biological differences between men and women are well known; however, literature addressing knowledge about the influence of sex on specific and general performance in team handball is almost nonexistent. Consequently, the aim of the study was to assess and compare specific and general physical performance in male and female elite team-handball players, to determine if the differences are consequential for general compared with specific physical performance characteristics and the relationship between general and specific physical performance.

METHODS

Twelve male and 10 female elite team-handball players performed a game-based performance test, upper- and lower-body strength and power tests, a sprinting test, and an incremental treadmill running test.

RESULTS

Significant differences (P < .05) between male and female players were found for peak oxygen uptake and total running time during the treadmill test, 30-m sprinting time, leg-extension strength, trunk- and shoulder-rotation torque, and countermovement-jump height, as well as offense and defense time, ball velocity, and jump height in the game-based performance test. An interaction (sex × test) was found for time and oxygen uptake, and except shoulder-rotation torque and ball velocity in women, the authors found only a low relationship between specific and general physical performance.

CONCLUSION

The results of the study revealed that male players are heavier, taller, faster, and stronger; jump higher; and have better aerobic performance. However, female players performed relatively better in the team-handball-specific tests than in the general tests. The findings also suggest that female players should focus more on strength training.

Individual and team performance in team-handball: a review

Team handball is a complex sport game that is determined by the individual performance of each player as well as tactical components and interaction of the team. The aim of this review was to specify the elements of team-handball performance based on scientific studies and practical experience, and to convey perspectives for practical implication. Scientific studies were identified via data bases of PubMed, Web of Knowledge, SPORT Discus, Google Scholar, and Hercules. A total of 56 articles met the inclusion criteria. In addition, we supplemented the review with 13 additional articles, proceedings and book sections. It was found that the specific characteristics of team-handball with frequent intensity changes, team-handball techniques, hard body confrontations, mental skills and social factors specify the determinants of coordination, endurance, strength and cognition. Although we found comprehensive studies examining individual performance in team-handball players of different experience level, sex or age, there is a lack of studies, particularly for team-handball specific training, as well as cognition and social factors. Key PointsThe specific characteristics of team-handball with frequent intensity changes, specific skills, hard body confrontations, mental skills and social factors define the determinants of coordination, endurance, strength and cognition.To increase individual and team performance in team-handball specific training based on these determinants have been suggested.Although there are comprehensive studies examining individual performance in team-handball players of different experience level, sex, or age are published, there is a lack of training studies, particularly for team-handball specific techniques and endurance, as well as cognition and social factors.