Inter-individual variability in performance benefits from repeated sprint training in hypoxia and associated training parameters.

This narrative review assesses the effects of repeated sprint training (RST) in hypoxia (RSH) and blood flow restriction (BFR) methods on skeletal muscle adaptations and performance. Current literature suggests that RSH promotes metabolic modifications in muscle cells, especially driven by reactive oxygen species production, HIF-1α stabilization, and changes in metabolism. Training with BFR promotes metabolite accumulation in working muscles due to limited blood flow, however, cellular mechanisms affected by BFR during RST are less explored. Data highlight that RSH improves repeated sprint ability (RSA) in several sport disciplines (e.g. rugby, tennis, soccer, cross-country skiing). However, recent studies showed that addition of hypoxia or BFR during RST did not promote supplementary benefits on aerobic performance, force-velocity power profile, and V ˙ O 2 max . Nonetheless, gains in V ˙ O 2 max were observed during sprint interval training protocols when BFR was applied during recovery between sets. Finally, recent studies highlighted that RSH can improve RSA in a short period. Thus, RSH and sprint training with BFR may be useful for sports disciplines requiring high glycolytic demand and can promote gains in RSA in a short window. Further studies must be encouraged to better understand the biological consequences of adding such stimuli to exercise, especially BFR, on long-term adaptation.

This case study reports the effects of six sessions of repeated sprint training in hypoxia (RSH) over 3 weeks on explosive power production capacity and repeated sprint ability (RSA) in two Japanese international‐level foil fencers. The six RSH sessions (60‐s sprints in total per session: consisting of two sets of five 6‐s sprints with 30‐s passive recovery, at simulated altitude of 3000 m) caused improvements of peak power output (PPO; Athlete A: 5.1%; Athlete B: 3.2%) and mean power output (MPO; Athlete A: 4.4%; Athlete B: 1.6%) over the 10 repeated sprints, respectively. The observed findings suggest that as few as six RSH sessions over 3 weeks can improve, at least to some extent, explosive power production capacity (PPO) and RSA (MPO) in the two elite fencers. To the best of our knowledge, this is the first study to apply short‐term RSH in combat sport (fencing) with international‐level athletes. Further studies are required to explore the effectiveness of short‐term RSH in combat sports with a more robust study design (e.g., randomized control trial with adequate statistical power) as the modality of RSH would suit physical and physiological demands in the majority of combat sports (e.g., wrestling, boxing).

Repeated-sprint training in hypoxia (RSH) was recently shown to improve repeated-sprint ability (RSA) in cycling. This phenomenon is likely to reflect fiber type-dependent, compensatory vasodilation, and therefore, our hypothesis was that RSH is even more beneficial for activities involving upper body muscles, such as double poling during cross-country skiing. In a double-blinded fashion, 17 competitive cross-country skiers performed six sessions of repeated sprints (each consisting of four sets of five 10-s sprints, with 20-s intervals of recovery) either in normoxia (RSN, 300 m; FiO2, 20.9%; n = 8) or normobaric hypoxia (RSH, 3000 m; FiO2, 13.8 %; n = 9). Before (pre) and after (post) training, performance was evaluated with an RSA test (10-s all-out sprints-20-s recovery, until peak power output declined by 30%) and a simulated team sprint (team sprint, 3 × 3-min all-out with 3-min rest) on a double-poling ergometer. Triceps brachii oxygenation was measured by near-infrared spectroscopy. From pretraining to posttraining, peak power output in the RSA was increased (P < 0.01) to the same extent (29% ± 13% vs 26% ± 18%, nonsignificant) in RSH and in RSN whereas the number of sprints performed was enhanced in RSH (10.9 ± 5.2 vs 17.1 ± 6.8, P < 0.01) but not in RSN (11.6 ± 5.3 vs 11.7 ± 4.3, nonsignificant). In addition, the amplitude in total hemoglobin variations during sprints throughout RSA rose more in RSH (P < 0.01). Similarly, the average power output during all team sprints improved by 11% ± 9% in RSH and 15% ± 7% in RSN. Our findings reveal greater improvement in the performance of repeated double-poling sprints, together with larger variations in the perfusion of upper body muscles in RSH compared with those in RSN.

Repeated-sprint training in hypoxia (RSH) has been shown as an efficient method for improving repeated-sprint ability (RSA) in team-sport players but has not been investigated in swimming. We assessed whether RSH with arterial desaturation induced by voluntary hypoventilation at low lung volume (VHL) could improve RSA to a greater extent than the same training performed under normal breathing (NB) conditions. Sixteen competitive swimmers completed 6 sessions of repeated sprints (2 sets of 16 × 15 m with 30 s send-off) either with VHL (RSH-VHL, n = 8) or with NB (RSN, n = 8). Before and after training, performance was evaluated through an RSA test (25-m all-out sprints with 35 s send-off) until exhaustion. From before to after training, the number of sprints was significantly increased in RSH-VHL (7.1 ± 2.1 vs 9.6 ± 2.5; P < .01) but not in RSN (8.0 ± 3.1 vs 8.7 ± 3.7; P = .38). Maximal blood lactate concentration ([La]max) was higher after than before in RSH-VHL (11.5 ± 3.9 vs 7.9 ± 3.7 mmol/L; P = .04) but was unchanged in RSN (10.2 ± 2.0 vs 9.0 ± 3.5 mmol/L; P = .34). There was a strong correlation between the increases in the number of sprints and in [La]max in RSH-VHL only (R = .93, P < .01). RSH-VHL improved RSA in swimming, probably through enhanced anaerobic glycolysis. This innovative method allows inducing benefits normally associated with hypoxia during swim training in normoxia.

Increased air temperature during repeated-sprint training in hypoxia amplifies muscle oxygenation flux without decreasing cycling performance

With minimal costs and travel constraints for athletes, the “living low-training high” (LLTH) approach is becoming an important intervention for modern sport. The popularity of the LLTH model of altitude training is also associated with the fact that it only causes a slight disturbance to athletes' usual daily routine, allowing them to maintain their regular lifestyle in their home environment. In this perspective article, we discuss the evolving boundaries of the LLTH paradigm and its practical applications for athletes. Passive modalities include intermittent hypoxic exposure at rest (IHE) and Ischemic preconditioning (IPC). Active modalities use either local [blood flow restricted (BFR) exercise] and/or systemic hypoxia [continuous low-intensity training in hypoxia (CHT), interval hypoxic training (IHT), repeated-sprint training in hypoxia (RSH), sprint interval training in hypoxia (SIH) and resistance training in hypoxia (RTH)]. A combination of hypoxic methods targeting different attributes also represents an attractive solution. In conclusion, a growing number of LLTH altitude training methods exists that include the application of systemic and local hypoxia stimuli, or a combination of both, for performance enhancement in many disciplines.

We examined the effects of high‐intensity training in normobaric hypoxia on aerobic capacity and exercise performance in horses and the individual response to normoxic and hypoxic training. Eight untrained horses were studied in a randomized, crossover design after training in hypoxia (HYP; 15.0% inspired O2) or normoxia (NOR; 20.9% inspired O2) 3 days/week for 4 weeks separated by a 4‐month washout period. Before and after each training period, incremental treadmill exercise tests were performed in normoxia. Each training session consisted of 1 min cantering at 7 m/s and 2 min galloping at the speed determined to elicit maximal oxygen consumption ( V˙O2max) in normoxia. Hypoxia increased significantly more than NOR in run time to exhaustion (HYP, +28.4%; NOR, +10.4%, p = .001), V˙O2max (HYP, +12.1%; NOR, +2.6%, p = .042), cardiac output ( Q˙; HYP, +11.3%; NOR, −1.7%, p = .019), and stroke volume (SV) at exhaustion (HYP, +5.4%; NOR, −5.5%, p = .035) after training. No significant correlations were observed between NOR and HYP for individual changes after training in run time (p = .21), V˙O2max (p = .99), Q˙ (p = .19), and SV (p = .46) at exhaustion. Arterial O2 saturation during exercise in HYP was positively correlated with the changes in run time (r = .85, p = .0073), Q˙ (r = .72, p = .043) and SV (r = .77, p = .026) of HYP after training, whereas there were no correlations between these parameters in NOR. These results suggest that high‐intensity training in normobaric hypoxia improved exercise performance and aerobic capacity of horses to a greater extent than the same training protocol in normoxia, and the severity of hypoxemia during hypoxic exercise might be too stressful for poor responders to hypoxic training.

Weakley, J, Castilla, AP, Ramos, AG, Banyard, H, Thurlow, F, Edwards, T, Morrison, M, McMahon, E, and Owen, C. The effect of traditional, rest redistribution, and velocity-based prescription on repeated sprint training performance and responses in semi-professional athletes. J Strength Cond Res 37(8): 1566-1572, 2023-The aim of this study was to investigate the effects of traditional, rest redistribution, and velocity-based repeated sprint training methods on repeated sprint performance, perceived effort, heart rate, and changes in force-velocity-power (FVP) profiles in male semiprofessional athletes. In a randomized crossover design, a traditional (2 sets of 6 repetitions [TRAD]), 2 different rest redistribution (4 sets of 3 repetitions [RR4] and 12 sets of 1 repetition [RR12]), and a 5% velocity loss (VL5%) (12 repetitions, with sets terminated when a 5% reduction in mean velocity had occurred) condition were completed. Mean and peak velocity, mean heart rate, and differential ratings of perceived exertion (dRPE) were measured throughout each session, while horizontal FVP profiles were assessed presession and postsession. The RR4 and RR12 conditions allowed the greatest maintenance of velocity, while the RR4, RR12, and VL5% had a moderate , significantly greater mean heart rate than the traditional condition. Trivial , nonsignificant differences between all conditions were observed in dRPE of the legs and breathlessness and FVP profiles. These findings indicate that rest redistribution can allow for greater maintenance of sprint velocity and heart rate, without altering perceived effort during repeated sprint training. In addition, velocity-loss thresholds may be a feasible method of prescription if athletes have diverse physical qualities and reductions in sprint performance during repeated sprint training are undesirable. Practitioners should consider these outcomes when designing repeated sprint training sessions because the strategic use of these methods can alter sprint performance and internal load without changing perceptions of intensity.

PURPOSE: This study was to determine the effects of body weight resistance training in hypoxia for 8 weeks on the skeletal muscle morphology and function. METHODS: Fourteen college age male students with no resistance training habits were divided into a normobaric hypoxic (FiO2 = 14.5%) training group (H, n = 7) or a normoxic (FiO2 = 20.9%) training group (N, n = 7). They completed resistance training two times per week for 8 weeks (a total of 16 sessions). The resistance training consisted of seven types of whole-body weight resistance training focusing on eccentric muscle contraction. Knee and elbow extension / flection strength (isometric strength, isokinetic strength, and muscular endurance), muscle thickness (rectus femoris and biceps brachii) and circumference (thigh and upper arm) were measured before and after training. During training session, SpO2 (all of sessions) and hart rate were monitored. Also, we measured growth hormone and cortisol at 10 training session. Each parameter was statistical analyzed by Wilcoxon signed rank tests were completed to identify any significant between-groups (p < 0.05). RESULTS: Elbow and Knee isometric and isokinetic strength tended to increase after training in both groups. But there was no significant difference in isometric and isokinetic strength between H and N groups. The % change of total work capacity in knee muscular endurance of H group tended to higher than that of N group. And, the % change of total work capacity in elbow of H group (108.8 ± 10.2%) was significantly higher than that of N group (96.0 ± 8.5%) (P < 0.05). The biceps brachii muscle thickness was significantly increased after training in the H group (110.2 ± 4.7%) compare with the N group (102.6 ± 3.3%) (P < 0.01). Also, rectus femoris muscle thickness, of H group tended to increase in compare with N group. CONCLUSIONS: It was suggested that body weight resistance training in hypoxia for 8 weeks increased muscle strength as well as traditional resistance training and would be improved muscular endurance and promoted muscle hypertrophy.

Introduction: The region between the ventilatory threshold (VT) and respiratory compensation point (RCP) is defined as the isocapnic buffering (ICB) phase and represents a phase of compensation for exercise-induced metabolic acidosis. There is sparse literature examining the effects of physical training on ICB phase in athletes. Objectives: The purpose of this study was to examine the effects of a repeated sprint training program on the ICB phase of college volleyball players. Methods: Eighteen male volleyball players were randomly assigned to either an experimental group (n=9) or a control group (n=9) and followed a traditional volleyball training program three times per week for six weeks. The experimental group additionally performed a repeated sprint training protocol immediately before each volleyball training session. Before and after the 6-week training period, all participants performed an incremental treadmill test to determine VT, RCP, and maximal oxygen uptake (VO2max). The ICB phases were calculated as VO2 (ml/kg/min) and sprint speed (km/h). Results: The experimental group showed significant improvements in ICB phase, RCP, VO2max and maximal sprint speed after training (p&lt;0.01). There were no significant changes in VT after training in the experimental group (p&gt;0.05). None of these variables changed significantly in the control group (p&gt;0.05). Conclusions: These findings indicate that repeated sprint training can enhance the ICB phase of volleyball players, which may be attributable to an improvement in buffering capacity leading to a shift in RCP towards higher intensities without any change in VT. The increase in the ICB phase may an important factor in terms of improvement in the high-intensity exercise tolerance of athletes. Level of Evidence II; Therapeutic studies - Investigating the results of treatment.

&lt;p&gt;This randomized controlled trial examined whether repeated-sprint training (RST) performed on sand or grass induces different adaptations in collegiate soccer players. Forty-two male players were randomly assigned to a sand-RST group (SAND, n = 14), a grass-RST group (GRASS, n = 14), or a control group (CON, n = 14). SAND and GRASS performed repeated-sprint training during two scheduled training sessions per week for six weeks, whereas CON completed standard technical soccer training of equivalent duration during the same two weekly sessions. All groups continued the same regular team training program, with the intervention delivered within two scheduled weekly sessions. Before and after the intervention, participants completed vertical jump tests including squat jump and countermovement jump, a running based anaerobic sprint test with peak, mean, and minimum power and fatigue index, and a graded treadmill test providing VO&lt;sub&gt;2max&lt;/sub&gt;, anaerobic threshold, and running economy. Baseline-adjusted analyses were conducted to examine between-group differences (ANCOVA for outcomes meeting model assumptions; mixed-design ANOVA when assumptions were violated). These analyses showed significant Group by Time interactions for all jump and running based sprint variables and for VO&lt;sub&gt;2max&lt;/sub&gt; and anaerobic threshold (p &amp;lt; 0.01), whereas the interaction for running economy was not significant (p = 0.15). Compared with GRASS, SAND showed greater improvements in squat jump (p &amp;lt; 0.01), mean power (p = 0.03), minimum power (p &amp;lt; 0.01), and fatigue index (p &amp;lt; 0.01). Aerobic adaptations were comparable between sand and grass, and no clear surface specific advantage was observed for running economy. In conclusion, implementing RST within scheduled team sessions improved jump performance, repeated-sprint performance indices, and aerobic fitness in collegiate soccer players, while sand-based training may provide greater benefits for squat jump and selected outcomes related to repeated-sprint fatigue resistance.&lt;/p&gt;

Die onderwerp wat in hierdie artikel bespreek word, is in die Suid-Afrikaanse reg relatief nuut en onontwikkeld. In hierdie artikel word verwysings na stieffamilieverhoudings beperk tot gevalle waar die biologiese ouer met haar of sy kinders in 'n huwelik of burgerlike vennootskap met 'n persoon wat nie 'n biologiese ouer is nie in 'n gemeenskaplike huishouding betrokke is. Sedert die beslissing van Heystek v Heystek, is hierdie aspek in Botha v Botha en in MB v NB in oenskou geneem. Die doel met hierdie artikel is om opnuut na die regsfundering van so 'n aanspraak binne die Suid-Afrikaanse reg te kyk. Die artikel word in vier hoofdele verdeel. Eerstens, sal die verskillende regsteoretiese funderings van die onderhoudsplig beskryf word. Daarna word die bespreking opgevolg deur 'n bondige bespreking van buitelandse reg, waarna die Suid-Afrikaanse reg as derde hoofdeel van nader beskou sal word. Die artikel word deur 'n slotbeskouing afgesluit. A step-child's maintenance claim against a step-parent In this article the foundation of a step-child's claim for maintenance against a step-parent is investigated. Primarily three foundations for a child's maintenance claim are revealed namely the formalistic and status based justification; the best interests of the child justification; and the functional justification. The first mentioned justification does not apply as foundation for the maintenance claim of the stepchild against the step-parent because the step-parent is not the natural or putative parent. The second justification focuses on the economic needs of children and the economic dislocation they suffer when formerly relied support from a step-parent is lost. The last justification pays attention to the social reality of relationships rather than to the formal characteristics thereof. Two reasons are given why the last mentioned justification applies to the maintenance claim of step-children. One, harm and compensation may serve as basis for the liability to pay maintenance. Two, the case where the step-parent takes over the role of parent the in loco parentis principle may serve as a foundation. The comparative law investigation reveals that the majority of foreign country systems grounds the claim on the in loco parentis principle. Different foundations for the claim are found in South African case law. The fact that the parties are married makes them liable for the maintenance of the common household. Two foundational possibilities arise from this. One, the consortium of the marriage grounds the maintenance obligation which is without any foundation in our law. Two, the obligation is founded upon the purchase for household necessaries. In a legal theoretical sense this is unacceptable because there are fundamental differences between the capacity to purchase household necessaries and a claim for maintenance. Section 28(1) (b) and (2) of the constitution are tabled as foundation for the claim. The fact that the step-parent acts in loco parentis grounds the obligation. Lastly, de facto adoption is also forwarded as foundation. The call on different justifications creates confusion and results in different answers. The maintenance of a child must primarily serve to satisfy the financial needs of the child and should focus less on the psychic and psychological support of the child. However, the economic reliance of the child on the support should also not be ignored. Therefore a combination of the reliance based justification and the in loco parentis foundation is advocated which I think is achieved in the MB case where section 28(1)(b) of the constitution in combination with the in loco parentis principle was applied.

Introduction: Coaches and athletes use hypoxic training (Live low, Train high), convinced of performance benefits over similar training at sea level. The purpose of this investigation was to document a performance benefit with a commonly used hypoxic training protocol in a blinded randomized cross-over design. Further, this study investigated several possible mechanisms for any improvements observed. We hypothesized that 3 weeks of hypoxic interval trainin would increase sea level performance and VO2 max compared to training at the same relative workload at sea level. Methods: 8 junior elite cyclists who were sea level residents (7 men, 1 woman, age 17 ± 1 years, weight 70.6 ± 7.8 kg, height 180 ± 5 cm) were recruited from the Norwegian high school for top athletes. Each subject underwent 2, three-week randomly assigned, training periods in our ônitrogen roomsö, one period in normoxia and the other in normobaric hypoxia (15% O2). A 5-week ôwashout periodö occurred between the training regimes. Each training period consisted of 9, 2-hour interval workouts, 3 per week at the subjects' individual La threshold. Heart rate, lactate, SpO2 and work (Kjoules) were recorded. Before and after each 3-week training period, the subjects performed a 30-minute time trial on their racing bike, a series of 5 submaximal workloads at increasing intensity and a VO2 max text on a stationary bike. Measurements done during the tests included VO2, ventilation, RQ, cardiac output, heart rate, lactate, SpO2, and arterial blood gases. Blood volume plasma volume and total red cell colume were measured at each time point (Evans blue dye). Results: During training there was a significant difference in absolute workload and oxygen content in the blood between the normoxic and the hypoxic group, while there were no differences in mean heart rate or lactate accumulated during training. Workload ± SD (watt): Normoxia: 245 ± 37, Hypoxia: 206 ± 32*. SpO2 ± SD (%): Normoxia: 96 ± 1, Hypoxia: 84 ± 3*. HR ± SD (bt/min: Normoxia: 163 ± 8, Hypoxia: 160 ± 7. Lactate ± SD (Mmol: Normoxia: 2.9 ± 0.2, Hypoxia: 3.2 ± 0.3. No significant differences were found in hematologic parameters at any time point (period 1 vs 2 or hypoxic vs normoxic). No significant changes were noted in maximal: power, VO2, VE (BTPS), heart rate, lactate, SpO2, RQ or time trial performance at any time point (period 1 vs 2 or hypoxic vs normoxic). Conclusions: We therefore conclude that 3 weeks of interval training at a simulated altitude of 3000 meter above sea level does not give an additional performance benefit at sea level compared to the same relative training a sea level. The hypoxic exposure is too brief to provide for any hematologic changes.

BackgroundThe rating of perceived exertion (RPE) scales with respiratory and muscular illustrations are recognized as simple and practical methods to understand individual psychometric characteristics in breathing and muscle exertion during exercise. However, the implementation of respiratory and muscular RPE to quantify training load in futsal training camps has not been examined. This study investigates respiratory and muscular RPE relationships during domestic training camps (DTC) and overseas training camps (OTC) in an under 20 futsal national team.MethodsData collected from eleven field players were used for comparison in this study (age = 18.7 ± 0.7 years, height = 171.9 ± 6.1 cm, body weight = 64.2 ± 8.4 kg). All players reported Borg CR10 RPE (RPECR10) and 7-scales respiratory RPE (RPErespiration) and muscular RPE (RPEmuscle) (Dalhousie pictorial scales) after training sessions and matches. Additionally, total distance covered (TD) and training impulse (TRIMP) were used to quantify external and internal loads via the Polar Team Pro system. Paired-sample t-tests were used to compare the RPECR10, RPErespiration, RPEmuscle, TD, and TRIMP between DTC and OTC. Furthermore, linear regression was performed to determine the relationships among all RPE scales, TD, and TRIMP.ResultsThe RPECR10 (p = 0.047), TD (p < 0.001), and TRIMP (p < 0.001) showed significant difference between DTC and OTC. Furthermore, linear regression analyses showed significant correlation between RPErespiration and RPEmuscle (DTC: r = 0.857, p = 0.006; OTC: r = 0.924, p < 0.001), RPECR10 and RPErespiration (DTC: r = 0.857, p = 0.001; OTC: r = 0.863, p = 0.001), and RPECR10 and RPEmuscle (DTC: r = 0.906, p < 0.001; OTC: r = 0.900, p < 0.001).ConclusionPictorial RPErespiration or RPEmuscle can be used as an alternative to quantify perceived measures of internal loads during DTC and OTC in futsal players. Interpretation of perceived measures of training load and cardiac-related responses in association with external training loads during short-term training camps would be useful in further understanding the demands of futsal players’ experience in these circumstances.

It is widely accepted that prolonged exposure to extreme altitude is detrimental for exercise performance and muscle structure. Moreover, highly trained subjects seem to suffer more under hypoxic conditions than untrained people. When using hypoxia as an ergogenic stimulus in athletes, it has thus become customary to limit hypoxia exposure in terms of altitude and duration of exposure in order to achieve defined physiologic goals. If hypoxia application is limited to the duration of training sessions, specific hypoxia responses on the molecular level in skeletal muscle tissue can be demonstrated. Hypoxia inducible factor 1 (HIF-1alpha mRNA) is upregulated after 6 weeks of endurance training in hypoxia (equivalent to an altitude of 3850 m) in previously untrained subjects. This upregulation is independent of training intensity but not observed in subjects training under similar conditions in normoxia. High intensity training in hypoxia further results in an increase of vascular endothelial growth factor (VEGF) mRNA, capillarity and myoglobin mRNA. These results suggest that hypoxia training results in improvements of the oxygen transfer capacity in skeletal muscle tissue. They thus offer a plausible explanation for the observation that effects of hypoxia training in athletes can best be demonstrated when performance tests are carried out in hypoxia. Beneficial effects of "training high-living low" for sea level performance of athletes can be inferred from the structural changes observed in muscle tissue; however, the functional improvements remain to be demonstrated directly.