Creatine supplementation and endurance performance: surges and sprints to win the race.

Creatine supplementation is an effective ergogenic aid to augment resistance training and improve intense, short duration, intermittent performance. The effects on endurance performance are less known. The purpose of this brief narrative review is to discuss the potential mechanisms of how creatine can affect endurance performance, defined as large muscle mass activities that are cyclical in nature and are >~3 min in duration, and to highlight specific nuances within the literature. Mechanistically, creatine supplementation elevates skeletal muscle phosphocreatine (PCr) stores facilitating a greater capacity to rapidly resynthesize ATP and buffer hydrogen ion accumulation. When co-ingested with carbohydrates, creatine enhances glycogen resynthesis and content, an important fuel to support high-intensity aerobic exercise. In addition, creatine lowers inflammation and oxidative stress and has the potential to increase mitochondrial biogenesis. In contrast, creatine supplementation increases body mass, which may offset the potential positive effects, particularly in weight-bearing activities. Overall, creatine supplementation increases time to exhaustion during high-intensity endurance activities, likely due to increasing anaerobic work capacity. In terms of time trial performances, results are mixed; however, creatine supplementation appears to be more effective at improving performances that require multiple surges in intensity and/or during end spurts, which are often key race-defining moments. Given creatines ability to enhance anaerobic work capacity and performance through repeated surges in intensity, creatine supplementation may be beneficial for sports, such as cross-country skiing, mountain biking, cycling, triathlon, and for short-duration events where end-spurts are critical for performance, such as rowing, kayaking, and track cycling.

Are Caffeine's Effects on Resistance Exercise and Jumping Performance Moderated by Training Status?

This study aimed to explore if the effects of caffeine intake on resistance exercise and jumping performance are moderated by training status. We included ten resistance-trained and ten recreationally active males in a randomized, double-blind, crossover study. Participants were categorized into groups according to their resistance to training experience and muscular strength levels. Exercise performance outcomes included weight lifted and mean velocity during a one-repetition maximum (1RM) bench press and squat; repetitions were performed to muscular failure in the same exercises with 70% of 1RM and countermovement jump (CMJ) height. Exercise performance was evaluated on three occasions, following no substance ingestion (control), caffeine (6 mg/kg), and placebo. There was a main effect on the condition for all the performance outcomes (all p ≤ 0.02), except for the 1RM squat mean velocity (p = 0.157) and 1RM bench press mean velocity (p = 0.719). For weight lifted in the 1RM bench press, there was a significant difference when comparing the caffeine vs. control, caffeine vs. placebo, and placebo vs. control. For weight lifted in the 1RM squat, a significant difference was found when comparing the caffeine vs. control. For muscular endurance outcomes and jump height, a significant difference was found when caffeine was compared to the control or placebo. Effect sizes were trivial for muscular strength (Hedges' g: 0.04-0.12), small for the jump height (Hedges' g: 0.43-0.46), and large for muscular endurance (Hedges' g: 0.89-1.41). Despite these ergogenic effects, there was no significant training status × caffeine interaction in any of the analyzed outcomes. In summary, caffeine ingestion is ergogenic for muscular strength, endurance, and jump height. These effects are likely to be of a similar magnitude in resistance-trained and recreationally active men.

Do older adults' beliefs about their community mobility predict walking performance?

Among older adults, preserving community mobility (CM) is important for maintaining independent living. We explored whether perceptions of the environment and self-efficacy for CM (SE-CM) would predict walking performance for tasks reflecting CM. We hypothesized that perceptions of the environment and SE-CM would be additive predictors of walking performance on tasks reflecting the complexity of CM. Independent living older adults (N = 60) aged 64-85 completed six complex walking tasks (CWTs), SE-CM, and the environmental analysis of mobility questionnaire (EAMQ). Multiple regression analyses indicated that for each CWT, the EAMQ scales predicted walking performance (range: model R2Adj. = .078 to .139, p < .04). However, when SE-CM was added to the models, it was the sole significant predictor (p < .05). Contrary to our hypotheses, SE-CM was the best predictor in the additive models. SE-CM may be more correspondent to walking tests and thus a more sensitive predictor of CM walking performance.

Stair falls: caregiver's "missed step" as a source of childhood fractures.

BACKGROUND: The purpose of this study was to describe fractures sustained by children and to analyze the associated costs when a caretaker falls down stairs while holding a child. MATERIALS AND METHODS: Between 2004 and 2012, 16 children who sustained a fracture after a fall down stairs while being carried by a caregiver were identified. Parents/caregivers were interviewed to see how the fall occurred, and a cost analysis was performed. RESULTS: The average age of the patients was 14.5 months (7-51 months). The lower extremity was involved in 15 of 16 fractures, with 8 involving the femur. The majority were buckle fractures, but all diaphyseal femur fractures were spiral. Three patients required a reduction in the operating room. All fractures healed with cast immobilization. Five patients underwent skeletal surveys, as the treating physicians were concerned about potential child abuse. The average cost of treatment was $6785 (range $948-45,876). Detailed histories from the caregivers showed that they "missed a step" due to the child being carried in front of the caregiver, obscuring their vision. CONCLUSIONS: A fall in a caregiver's arms while going down stairs can result in multiple orthopedic injuries. The costs of treating these injuries are not insignificant, and the suspicion of child abuse can be both costly and unnecessary in the case of a true accident. While descending the stairs with a child in their arms, the caregiver should hold the child to the side so as not to obscure their vision of the step with one arm, ideally holding the handrail with the other. LEVEL OF EVIDENCE: IV case series.