Sleeping with low carbohydrate (CHO) availability is a dietary strategy that may enhance training adaptation. However, the impact on an athlete’s health is unclear. This study quantified the effect of a short-term “sleep-low” dietary intervention on markers of iron regulation and immune function in athletes. In a randomized, repeated-measures design, 11 elite triathletes completed two 4-day mixed cycle run training blocks. Key training sessions were structured such that a high-intensity training session was performed in the field on the afternoon of Days 1 and 3, and a low-intensity training (LIT) session was performed on the following morning in the laboratory (Days 2 and 4). The ingestion of CHO was either divided evenly across the day (HIGH) or restricted between the high-intensity training and LIT sessions, so that the LIT session was performed with low CHO availability (LOW). Venous blood and saliva samples were collected prior to and following each LIT session and analyzed for interleukin-6, hepcidin 25, and salivary immunoglobulin-A. Concentrations of interleukin-6 increased acutely after exercise (p < .001), but did not differ between dietary conditions or days. Hepcidin 25 increased 3-hr postexercise (p < .001), with the greatest increase evident after the LOW trial on Day 2 (2.5 ± 0.9 fold increase ±90% confidence limit). The salivary immunoglobulin-A secretion rate did not change in response to exercise; however, it was highest during the LOW condition on Day 4 (p = .046). There appears to be minimal impact to markers of immune function and iron regulation when acute exposure to low CHO availability is undertaken with expert nutrition and coaching input.
Alannah K. A. McKay, Ida A. Heikura, Louise M. Burke, Peter Peeling, David B. Pyne, Rachel P.L. van Swelm, Coby M. Laarakkers and Gregory R. Cox
Craig Pickering and Jozo Grgic
Caffeine is a well-established ergogenic aid, with its performance-enhancing effects demonstrated across a wide variety of exercise modalities. Athletes tend to frequently consume caffeine as a performance enhancement method in training and competition. There are a number of methods available as a means of consuming caffeine around exercise, including caffeine anhydrous, sports drinks, caffeine carbohydrate gels, and gum. One popular method of caffeine ingestion in nonathletes is coffee, with some evidence suggesting it is also utilized by athletes. In this article, we discuss the research pertaining to the use of coffee as an ergogenic aid, exploring (a) whether caffeinated coffee is ergogenic, (b) whether dose-matched caffeinated coffee provides a performance benefit similar in magnitude to caffeine anhydrous, and (c) whether decaffeinated coffee consumption affects the ergogenic effects of a subsequent isolated caffeine dose. There is limited evidence that caffeinated coffee has the potential to offer ergogenic effects similar in magnitude to caffeine anhydrous; however, this requires further investigation. Coingestion of caffeine with decaffeinated coffee does not seem to limit the ergogenic effects of caffeine. Although caffeinated coffee is potentially ergogenic, its use as a preexercise caffeine ingestion method represents some practical hurdles to athletes, including the consumption of large volumes of liquid and difficulties in quantifying the exact caffeine dose, as differences in coffee type and brewing method may alter caffeine content. The use of caffeinated coffee around exercise has the potential to enhance performance, but athletes and coaches should be mindful of the practical limitations.
Guillaume P. Ducrocq, Thomas J. Hureau, Olivier Meste and Grégory M. Blain
Context: Drop jumps and high-intensity interval running are relevant training methods to improve explosiveness and endurance performance, respectively. Combined training effects might, however, be achieved by performing interval drop jumping. Purpose: To determine the acute effects of interval drop jumping on oxygen uptake (
Blake D. McLean, Kevin White, Christopher J. Gore and Justin Kemp
Purpose: There is debate as to which environmental intervention produces the most benefit for team sport athletes, particularly comparing heat and altitude. This quasi-experimental study aimed to compare blood volume (BV) responses with heat and altitude training camps in Australian footballers. Methods: The BV of 7 professional Australian footballers (91.8 [10.5] kg, 191.8 [10.1] cm) was measured throughout 3 consecutive spring/summer preseasons. During each preseason, players participated in altitude (year 1 and year 2) and heat (year 3) environmental training camps. Year 1 and year 2 altitude camps were in November/December in the United States, whereas the year 3 heat camp was in February/March in Australia after a full exposure to summer heat. BV, red cell volume, and plasma volume (PV) were measured at least 3 times during each preseason. Results: Red cell volume increased substantially following altitude in both year 1 (d = 0.67) and year 2 (d = 1.03), before returning to baseline 4 weeks postaltitude. Immediately following altitude, concurrent decreases in PV were observed during year 1 (d = −0.40) and year 2 (d = −0.98). With spring/summer training in year 3, BV and PV were substantially higher in January than temporally matched postaltitude measurements during year 1 (BV: d = −0.93, PV: d = −1.07) and year 2 (BV: d = −1.99, PV: d = −2.25), with year 3 total BV, red cell volume, and PV not changing further despite the 6-day heat intervention. Conclusions: We found greater BV after training throughout spring/summer conditions, compared with interrupting spring/summer exposure to train at altitude in the cold, with no additional benefits observed from a heat camp following spring/summer training.
Olfa Turki, Wissem Dhahbi, Sabri Gueid, Sami Hmaied, Marouen Souaifi and Riadh Khalifa
Purpose: To explore the effect of 4 different warm-up strategies using weighted vests and to determine the specific optimal recovery duration required to optimize the repeated change-of-direction (RCOD) performance in young soccer players. Methods: A total of 19 male soccer players (age 18 [0.88] y, body mass 69.85 [7.68] kg, body height 1.75 [0.07] m, body mass index 22.87 [2.23] kg·m−2, and body fat percentage 12.53% [2.59%]) completed the following loaded warm-up protocols in a randomized, counterbalanced cross-over, within-participants order and on separate days: weighted vest with a loading of 5% (WUV5%), 10% (WUV10%), 15% (WUV15%) body mass, and an unloaded condition (control). RCOD performance (total time, peak time, and fatigue index) was collected during the preintervention phase (5 min after the dynamic stretching sequence) for baseline values and immediately (at 15 min), at 4- and 8-minute postwarm-up intervention. Results: For each postwarm-up tested, recovery times (ie, 15 s, 4 min, and 8 min), of both total and peak times were faster following WUV5%, WUV10%, and WUV15%, compared with the unloaded condition (P ≤.001–.031, d = 1.28–2.31 [large]). There were no significant differences (P = .09–1.00, d = 0.03–0.72 [trivial–moderate]) in-between recovery times in both total and peak times following WUV5%, WUV10%, and WUV15%. However, baseline fatigue index score was significantly worse than all other scores (P ≤.001–.002, d = 1.35–2.46 [large]) following the loaded conditions. Conclusions: The findings demonstrated that a dynamic loaded warm-up increases an athlete’s initial RCOD performance up to the 8-minute postwarm-up intervention. Therefore, strength coaches need to consider using weighted vests during the warm-up for trained athletes in order to acutely optimize RCODs.
Carl Foster, Jos J. de Koning, Christian Thiel, Bram Versteeg, Daniel A. Boullosa, Daniel Bok and John P. Porcari
Background: Pacing studies suggest the distribution of effort for optimizing performance. Cross-sectional studies of 1-mile world records (WRs) suggest that WR progression includes a smaller coefficient of variation of velocity. Purpose: This study evaluates whether intraindividual pacing used by elite runners to break their own WR (1 mile, 5 km, and 10 km) is related to the evolution of pacing strategy. We provide supportive data from analysis in subelite runners. Methods: Men’s WR performances (with 400-m or 1-km splits) in 1 mile, 5 km, and 10 km were retrieved from the IAAF database (from 1924 to present). Data were analyzed relative to pacing pattern when a runner improved their own WR. Similar analyses are presented for 10-km performance in subelite runners before and after intensified training. Results: WR performance was improved in 1 mile (mean [SD]: 3:59.4 [11.2] to 3:57.2 [8.6]), 5 km (13:27 [0:33] to 13:21 [0:33]), and 10 km (28:35 [1:27] to 28:21 [1:21]). The average coefficient of variation did not change in the 1 mile (3.4% [1.8%] to 3.6% [1.6%]), 5 km (2.4% [0.9%] to 2.2% [0.8%]), or 10 km (1.4% [0.1%] to 1.5% [0.6%]) with improved WR. When velocity was normalized to the percentage mean velocity for each race, the pacing pattern was almost identical. Very similar patterns were observed in subelite runners in the 10 km. When time improved from 49:20 (5:30) to 45:56 (4:58), normalized velocity was similar, terminal RPE increased (8.4 [1.6] to 9.1 [0.8]), coefficient of variation was unchanged (4.4% [1.1%] to 4.8% [2.1%]), and VO2max increased (49.8 [7.4] to 55.3 [8.8] mL·min−1·kg−1). Conclusion: The results suggest that when runners break their own best performances, they employ the same pacing pattern, which is different from when WRs are improved in cross-sectional data.
Irineu Loturco, Timothy Suchomel, Chris Bishop, Ronaldo Kobal, Lucas A. Pereira and Michael R. McGuigan
Purpose: To identify the bar velocities that optimize power output in the barbell hip thrust exercise. Methods: A total of 40 athletes from 2 sports disciplines (30 track-and-field sprinters and jumpers and 10 rugby union players) participated in this study. Maximum bar-power outputs and their respective bar velocities were assessed in the barbell hip thrust exercise. Athletes were divided, using a median split analysis, into 2 groups according to their bar-power outputs in the barbell hip thrust exercise (“higher” and “lower” power groups). The magnitude-based inferences method was used to analyze the differences between groups in the power and velocity outcomes. To assess the precision of the bar velocities for determining the maximum power values, the coefficient of variation (CV%) was also calculated. Results: Athletes achieved the maximum power outputs at a mean velocity, mean propulsive velocity, and peak velocity of 0.92 (0.04) m·s−1 (CV: 4.1%), 1.02 (0.05) m·s−1 (CV: 4.4%), and 1.72 (0.14) m·s−1 (CV: 8.4%), respectively. No meaningful differences were observed in the optimum bar velocities between higher and lower power groups. Conclusions: Independent of the athletes’ power output and bar-velocity variable, the optimum power loads frequently occur at very close bar velocities.
Jonathon Weakley, Carlos Ramirez-Lopez, Shaun McLaren, Nick Dalton-Barron, Dan Weaving, Ben Jones, Kevin Till and Harry Banyard
Purpose: Prescribing resistance training using velocity loss thresholds can enhance exercise quality by mitigating neuromuscular fatigue. As little is known regarding performance during these protocols, we aimed to assess the effects of 10%, 20%, and 30% velocity loss thresholds on kinetic, kinematic, and repetition characteristics in the free-weight back squat. Methods: Using a randomized crossover design, 16 resistance-trained men were recruited to complete 5 sets of the barbell back squat. Lifting load corresponded to a mean concentric velocity (MV) of ∼0.70 m·s−1 (115  kg). Repetitions were performed until a 10%, 20%, or 30% MV loss was attained. Results: Set MV and power output were substantially higher in the 10% protocol (0.66 m·s−1 and 1341 W, respectively), followed by the 20% (0.62 m·s−1 and 1246 W) and 30% protocols (0.59 m·s−1 and 1179 W). There were no substantial changes in MV (−0.01 to −0.02 m·s−1) or power output (−14 to −55 W) across the 5 sets for all protocols, and individual differences in these changes were typically trivial to small. Mean set repetitions were substantially higher in the 30% protocol (7.8), followed by the 20% (6.4) and 10% protocols (4.2). There were small to moderate reductions in repetitions across the 5 sets during all protocols (−39%, −31%, −19%, respectively), and individual differences in these changes were small to very large. Conclusions: Velocity training prescription maintains kinetic and kinematic output across multiple sets of the back squat, with repetition ranges being highly variable. Our findings, therefore, challenge traditional resistance training paradigms (repetition based) and add support to a velocity-based approach.
Antonio Dello Iacono, Marco Beato and Israel Halperin
Purpose: To compare the effects of 2 postactivation potentiation (PAP) protocols using traditional-set or cluster-set configurations on countermovement jump performance. Methods: Twenty-six male basketball players completed 3 testing sessions separated by 72 hours. On the first session, subjects performed barbell jump squats with progressively heavier loads to determine their individual optimum power load. On the second and third sessions, subjects completed 2 PAP protocols in a randomized order: 3 sets of 6 repetitions of jump squats using optimum power load performed with either a traditional-set (no interrepetition rest) or a cluster-set (20-s rest every 2 repetitions) configuration. After a warm-up, countermovement jump height was measured using a force platform before, 30 seconds, 4 minutes, and 8 minutes after completing the PAP protocols. The following kinetic variables were also analyzed and compared: relative impulse, ground reaction force, eccentric displacement, and vertical leg-spring stiffness. Results: Across both conditions, subjects jumped lower at post 30 seconds by 1.21 cm, and higher in post 4 minutes by 2.21 cm, and in post 8 minutes by 2.60 cm compared with baseline. However, subjects jumped higher in the cluster condition by 0.71 cm (95% confidence interval, 0.37 to 1.05 cm) in post 30 seconds, 1.33 cm (95% confidence interval, 1.02 to 1.65 cm) in post 4 minute, and 1.64 cm (95% confidence interval, 1.41 to 1.88 cm) in post 8 minutes. The superior countermovement jump performance was associated with enhanced kinetic data. Conclusions: Both protocols induced PAP responses in vertical jump performance using jump squats at optimum power load. However, the cluster-set configuration led to superior performance across all time points, likely due to reduced muscular fatigue.
Rebecca Quinlan and Jessica A. Hill
Purpose: To investigate the effects of supplementation with tart cherry juice (TCJ) on markers of recovery after intermittent exercise under habitual dietary conditions. Methods: Using a randomized, single-blind, placebo (PLA)-controlled, independent-groups design, 20 team-sport players (8 male and 12 female; age 26  y, height 175.4 [9.6] cm, body mass 70.2 [12.6] kg) were divided equally into 2 groups and consumed either TCJ or PLA twice per day for 8 consecutive days while following their normal dietary habits. Participants completed an adapted version of the Loughborough Intermittent Shuttle Test (LIST) on day 6 of supplementation. Countermovement jump, 20-m sprint, maximal voluntary isometric contraction, and delayed onset muscle soreness were assessed at baseline and 1, 24, and 48 hours post-LIST. Blood markers of muscle damage (creatine kinase) and inflammation (C-reactive protein) were taken presupplementation, immediately pre-LIST, and 1, 24, and 48 hours post-LIST. Data were analyzed using a repeated-measures analysis of variance. Results: Countermovement jump, 20-m sprint, and maximal voluntary isometric contraction showed significantly faster recovery with TCJ (P < .05) at 24 and 48 hours post-LIST. A significant interaction effect (P < .05) was observed for muscle soreness; however, Bonferroni post hoc analysis could not identify when the significant differences between TCJ and PLA occurred. There were no significant differences throughout recovery between TCJ and PLA for C-reactive protein and creatine kinase (P < .05). Conclusion: The results suggest that TCJ, in addition to habitual diet, can accelerate recovery after intermittent exercise and therefore extend the efficacy of TCJ in accelerating recovery in team sports.