Jockeys are unique given that they make weight daily and, therefore, often resort to fasting and dehydration. Through increasing daily food frequency (during energy deficit), we have reported short-term improvements in jockey’s body composition. While these changes were observed over 6–12 weeks with food provided, it is unclear whether such improvements can be maintained over an extended period during free-living conditions. We, therefore, assessed jockeys over 5 years using dual X-ray absorptiometry, resting metabolic rate, and hydration measurements. Following dietary and exercise advice, jockeys reduced fat mass from baseline of 7.1 ± 1.4 kg to 6.1 ± 0.7 kg and 6.1 ± 0.6 kg (p < .001) at Years 1 and 5, respectively. In addition, fat-free mass was maintained with resting metabolic rate increasing significantly from 1,500 ± 51 kcal/day at baseline to 1,612 ± 95 kcal/day and 1,620 ± 92 kcal/day (p < .001) at Years 1 and 5, respectively. Urine osmolality reduced from 816 ± 236 mOsmol/L at baseline to 564 ± 175 mOsmol/L and 524 ± 156 mOsmol/L (p < .001) at Years 1 and 5, respectively. The percent of jockeys consuming a regular breakfast significantly increased from 48% at baseline to 83% (p = .009) and 87% (p = .003) at Years 1 and 5, alongside regular lunch from 35% to 92% (p < .001) and 96% (p < .001) from baseline to Years 1 and 5, respectively. In conclusion, we report that improved body composition can be maintained in free-living jockeys over a 5-year period when appropriate guidance has been provided.
George Wilson, Carl Langan-Evans, Dan Martin, Andreas M. Kasper, James P. Morton, and Graeme L. Close
Charlie R. Ottinger, James J. Tufano, Kristen C. Cochrane-Snyman, Raad H. Gheith, and Jeffrey M. McBride
Purpose: The purpose of this study was to explore whether offset loading in the barbell squat altered ground-reaction force (GRF) and muscle activation in the dominant (D) and nondominant (ND) lower limb compared to traditional squats. Methods: Twelve well-trained men (age 26.4 [3.2] y; 10.3 [1.9] y experience) performed 3 sets of 10 repetitions at 60% of their previously measured 1-repetition maximum. Sets were quasi-randomized between traditional loading (TDL), dominant-side offset loading (OS-D), and nondominant-side offset loading (OS-ND). All repetitions were performed on a dual force plate with electromyography sensors on the prime mover muscles of the squat. GRF symmetry was assessed using the symmetry index (SI) to determine the direction (D [+] or ND [−]) and magnitude (%) of the asymmetry. Finally, the first 3 and final 3 repetitions of each set were compared for compensatory changes in symmetry. Results: OS-D induced a significant change in limb SI relative to TDL (5.21% vs 1.44%; P = .011); however, no significant difference in limb SI was seen between TDL and OS-ND (−0.66% vs 1.44%; P = .278). No asymmetries between D and ND muscle activation were present in any condition. TDL and OS-D squats exhibited significant improvements in limb SI between the first 3 and final 3 repetitions (P = .035 and .011, respectively); however, no such improvement was seen in OS-ND. Conclusions: OS-D is capable of significantly altering GRF limb SI in a bilateral squat; however, OS-ND appears to exhibit no GRF or electromyography effects relative to TDL. Thus, the results of this study do not support the use of OS-ND in the pursuit of strengthening a weaker limb, suggesting that unilateral training may be a preferred mode of exercise for this desired outcome.
Larissa Di Bella, Kenji Doma, Wade Heath Sinclair, and Jonathan Douglas Connor
Purpose: This crossover trial compared the effects of varying feedback approaches on sprint performance, motivation, and affective mood states in female athletes. Methods: Eligibility criteria were being competitive female athletes, where participants completed sprint tests in 4 randomized feedback conditions on grass, including augmented feedback (sprint time; AUG-FB), technical feedback (cues; TECH-FB), a competition-driven drill (CDD) sprinting against an opponent, and a control condition (no feedback; CON). Participants completed a 20-m sprint (maximum sprint), 30-m curved agility sprint, and a repeated sprint ability test, with sprint times, motivation level, and mood states recorded. The participants were blinded from the number of trials during the repeated sprint ability test. Results: About 12 rugby league players completed all feedback conditions. The maximum sprint times were faster for AUG-FB (3.54 [0.16] s) and CDD (3.54 [0.16] s) compared with TECH-FB (3.64 [0.16] s), while there were no differences compared with CON (3.58 [0.17] s). The curved agility sprint times were faster for AUG-FB (5.42 [0.20] s) compared with TECH-FB (5.61 [0.21] s) and CON (5.57 [0.24] s), although CDD (5.38 [0.26] s) produced faster sprint times than TECH-FB. Effort and value were higher with AUG-FB (6.31 [0.68]; 6.53 [0.05]) compared with CON (5.99 [0.60]; 4.75 [2.07]), while CON exhibited lower enjoyment ratings (4.68 [0.95]) compared with other feedback conditions (AUG-FB: 5.54 [0.72]; CDD: 5.56 [0.67]; TECH-FB: 5.60 [0.56]). Conclusions: Providing AUG-FB prior to sprint tasks enhances more immediate performance outcomes than TECH-FB. AUG-FB also benefited athlete enjoyment, task effort, and coaching value. Female athletes should receive AUG-FB in testing and training environments, to improve immediate physical performance and motivation.
Scott A. Conger, Lara M. Tuthill, and Mindy L. Millard-Stafford
Whether caffeine (CAF) increases fat metabolism remains debatable. Using systematic review coupled with meta-analysis, our aim was to determine effects of CAF on fat metabolism and the relevant factors moderating this effect. Electronic databases PubMed, SPORTDiscus, and Web of Science were searched using the following string: CAF AND (fat OR lipid) AND (metabolism OR oxidation). A meta-analytic approach aggregated data from 94 studies examining CAF’s effect on fat metabolism assessed by different biomarkers. The overall effect size (ES) was 0.39 (95% confidence interval [CI] [0.30, 0.47], p < .001), indicating a small effect of CAF to increase fat metabolism; however, ES was significantly higher (p < .001) based on blood biomarkers (e.g., free fatty acids, glycerol) (ES = 0.55, 95% CI [0.43, 0.67]) versus expired gas analysis (respiratory exchange ratio, calculated fat oxidation) (ES = 0.26, 95% CI [0.16, 0.37]), although both were greater than zero. Fat metabolism increased to a greater extent (p = .02) during rest (ES = 0.51, 95% CI [0.41, 0.62]) versus exercise (ES = 0.35, 95% CI [0.26, 0.44]) across all studies, although ES was not different for studies reporting both conditions (ES = 0.49 and 0.44, respectively). There were no subgroup differences based on participants’ fitness level, sex, or CAF dosage. CAF ingestion increases fat metabolism but is more consistent with blood biomarkers versus whole-body gas exchange measures. CAF has a small effect during rest across all studies, although similar to exercise when compared within the same study. CAF dosage did not moderate this effect.
David J. Scott, Phil Marshall, Samuel T. Orange, and Massimiliano Ditroilo
Purpose: To compare the effects of variable-resistance complex training (VRCT) versus traditional complex training (TCT) on muscle architecture in rugby league players during a 6-week mesocycle. Methods: Twenty-four rugby league players competing in the British University & Colleges Sport (BUCS) Premier North Division were randomized to VRCT (n = 8), TCT (n = 8), or control (n = 8). Experimental groups completed a 6-week lower-body complex training intervention (2×/wk), which involved alternating high-load resistance exercise with plyometric exercise in the same session. The VRCT group performed resistance exercises at 70% of 1-repetition maximum (1RM) + 0% to 23% of 1RM from band resistance with a 90-second intracontrast rest interval, whereas the TCT group performed resistance exercise at 93% of 1RM with a 4-minute intracontrast rest interval. Muscle thickness (MT), pennation angle, and fascicle length (L f) were assessed for the vastus lateralis (VL) and gastrocnemius medialis using ultrasound imaging. Results: Both TCT and VRCT groups significantly improved VL MT and VL L f compared with control (all P < .05). Standardized within-group changes in MT and L f (Cohen d av ± 95% CI) were moderate for TCT (d av = 0.91 ± 1.0; d av = 1.1 ± 1.1) and unclear for VRCT (d av = 0.44 ± 0.99; d av = 0.47 ± 0.99), respectively. Differences in change scores between TCT and VRCT were unclear. Conclusions: VRCT and TCT can be utilized during the competitive season to induce favorable MT and L f muscle architecture adaptations for the VL. TCT may induce greater muscle architecture adaptations of the VL, whereas VRCT may be of more practical value given the shorter intracontrast rest interval between resistance and plyometric exercises.
David J. Scott, Massimiliano Ditroilo, Samuel T. Orange, and Phil Marshall
Purpose: To compare the effects of variable-resistance complex training (VRCT) versus traditional complex training (TCT) on strength, power, speed, and leg stiffness (Kleg) in rugby league players during a 6-week mesocycle. Methods: Twenty-four rugby league players competing in the British University and Colleges Sport Premier North Division were randomized to VRCT (n = 8), TCT (n = 8), or control (CON; n = 8). Experimental groups completed a 6-week lower-body complex training intervention (2×/wk) that involved alternating high-load resistance exercise with plyometric exercise within the same session. The VRCT group performed resistance exercises at 70% of 1-repetition maximum (1RM) + 0% to 23% of 1RM from band resistance with a 90-second intracontrast rest interval, whereas the TCT group performed resistance exercise at 93% of 1RM with a 4-minute intracontrast rest interval. Back-squat 1RM, countermovement jump peak power, reactive strength index, sprint times, and Kleg were assessed pretraining and posttraining. Results: VRCT and TCT significantly improved 1RM back squat, countermovement jump peak power, and 5-m sprint time (all P < .05). VRCT also improved Kleg, whereas TCT improved 10- and 20-m sprint times (all P < .05). Between groups, both VRCT and TCT improved 1RM back squat compared with CON (both P < .001). Additionally, VRCT improved Kleg compared with CON (right leg: P = .016) and TCT improved 20-m sprint time compared with CON (P = .042). Conclusions: VRCT and TCT can be implemented during the competitive season to improve strength, power, and 5-m sprint time. VRCT may lead to greater improvements in reactive strength index and Kleg, whereas TCT may enhance 10- and 20-m sprint times.
Anders Skoglund, Martin Frank Strand, and Thomas A. Haugen
Purpose: Submaximal sprinting allows for larger accumulated work to be reached before the onset of fatigue, compared with maximal efforts. The aim of this study was to investigate the effect of sprint running at 90% to 95% of maximal velocity (V max) on sprint performance. Methods: Recreationally active adults were randomly assigned into a control group (n = 12, 27  y, 172  cm, 72  kg) and a training group (n = 14, 26  y, 171  cm, 69  kg). Both groups completed pretesting and posttesting in form of a 30-m sprint separated by a 6-week period. The training group performed a weekly sprint-training session consisting of 30-m flying sprints at 90% to 95% of V max, while the control group performed no intervention training. Results: Significant improvements in the training group were observed for 10- (P = .003), 20- (P = .001), and 30-m sprint time (P = .002). These improvements were accompanied by higher step rate (P = .006) and theoretical V max (P = .007) and maximal power (P = .004). Significant between-groups differences were observed for 10- (P = .008), 20- (P < .001), and 30-m sprint time (P < .001), as well as for step rate (P = .015), theoretical V max (P = .016), and maximal power (P = .008). All within- and between-groups differences were in the range of trivial to small. Conclusion: Sprint running at 90% to 95% of V max can enhance 10- to 30-m sprint performance in recreationally active adults.
Tom P. Aird, Andrew J. Farquharson, Kate M. Bermingham, Aifric O’Sullivan, Janice E. Drew, and Brian P. Carson
Endurance training in fasted conditions (FAST) induces favorable skeletal muscle metabolic adaptations compared with carbohydrate feeding (CHO), manifesting in improved exercise performance over time. Sprint interval training (SIT) is a potent metabolic stimulus, however nutritional strategies to optimize adaptations to SIT are poorly characterized. Here we investigated the efficacy of FAST versus CHO SIT (4–6 × 30-s Wingate sprints interspersed with 4-min rest) on muscle metabolic, serum metabolome and exercise performance adaptations in a double-blind parallel group design in recreationally active males. Following acute SIT, we observed exercise-induced increases in pan-acetylation and several genes associated with mitochondrial biogenesis, fatty acid oxidation, and NAD+-biosynthesis, along with favorable regulation of PDK4 (p = .004), NAMPT (p = .0013), and NNMT (p = .001) in FAST. Following 3 weeks of SIT, NRF2 (p = .029) was favorably regulated in FAST, with augmented pan-acetylation in CHO but not FAST (p = .033). SIT induced increases in maximal citrate synthase activity were evident with no effect of nutrition, while 3-hydroxyacyl-CoA dehydrogenase activity did not change. Despite no difference in the overall serum metabolome, training-induced changes in C3:1 (p = .013) and C4:1 (p = .010) which increased in FAST, and C16:1 (p = .046) and glutamine (p = .021) which increased in CHO, were different between groups. Training-induced increases in anaerobic (p = .898) and aerobic power (p = .249) were not influenced by nutrition. These findings suggest some beneficial muscle metabolic adaptations are evident in FAST versus CHO SIT following acute exercise and 3 weeks of SIT. However, this stimulus did not manifest in differential exercise performance adaptations.
Stephen P. Fenemor, Matthew W. Driller, Nicholas D. Gill, Brad Anderson, Julia R. Casadio, Stacy T. Sims, and C. Martyn Beaven
Purpose: Although recommendations for effective heat acclimation (HA) strategies for many circumstances exist, best-practice HA protocols specific to elite female team-sport athletes are yet to be established. Therefore, the authors aimed to investigate the effectiveness and retention of a passive HA protocol integrated in a female Olympic rugby sevens team training program. Methods: Twelve elite female rugby sevens athletes undertook 10 days of passive HA across 2 training weeks. Tympanic temperature (T Tymp), sweat loss, heart rate, and repeated 6-second cycling sprint performance were assessed using a sport-specific heat stress test Pre-HA, after 3 days (Mid-HA), after 10 days (Post-HA), and 15 days post-HA (Decay). Results: Compared with Pre-HA, submaximal T Tymp was lower Mid-HA and Post-HA (both by −0.2 [0.7] °C; d ≥ 0.71), while resting T Tymp was lower Post-HA (by −0.3 [0.2] °C; d = 0.81). There were no differences in T Tymp at Decay compared with Pre-HA, nor were there any differences in heart rate or sweat loss at any time points. Mean peak 6-second power output improved Mid-HA and Post-HA (76  W; 75  W, respectively; d ≥ 0.45) compared with Pre-HA. The observed performance improvement persisted at Decay by 65 (45) W (d = 0.41). Conclusions: Ten days of passive HA can elicit some thermoregulatory and performance benefits when integrated into a training program in elite female team-sport athletes. However, such a protocol does not provide a sufficient thermal impulse for thermoregulatory adaptations to be retained after 15 days with no further heat stimulus.