Active Preconditioning With Blood Flow Restriction or/and Systemic Hypoxic Exposure Does Not Improve Repeated Sprint Cycling Performance

Sprint training in hypoxia and with blood flow restriction: Controversies and perspectives

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.

Muscle Oximetry in Sports Science: An Updated Systematic Review

BACKGROUND

In the last 5 years since our last systematic review, a significant number of articles have been published on the technical aspects of muscle near-infrared spectroscopy (NIRS), the interpretation of the signals and the benefits of using the NIRS technique to measure the physiological status of muscles and to determine the workload of working muscles.

OBJECTIVES

Considering the consistent number of studies on the application of muscle oximetry in sports science published over the last 5 years, the objectives of this updated systematic review were to highlight the applications of muscle oximetry in the assessment of skeletal muscle oxidative performance in sports activities and to emphasize how this technology has been applied to exercise and training over the last 5 years. In addition, some recent instrumental developments will be briefly summarized.

METHODS

Preferred Reporting Items for Systematic Reviews guidelines were followed in a systematic fashion to search, appraise and synthesize existing literature on this topic. Electronic databases such as Scopus, MEDLINE/PubMed and SPORTDiscus were searched from March 2017 up to March 2023. Potential inclusions were screened against eligibility criteria relating to recreationally trained to elite athletes, with or without training programmes, who must have assessed physiological variables monitored by commercial oximeters or NIRS instrumentation.

RESULTS

Of the identified records, 191 studies regrouping 3435 participants, met the eligibility criteria. This systematic review highlighted a number of key findings in 37 domains of sport activities. Overall, NIRS information can be used as a meaningful marker of skeletal muscle oxidative capacity and can become one of the primary monitoring tools in practice in conjunction with, or in comparison with, heart rate or mechanical power indices in diverse exercise contexts and across different types of training and interventions.

CONCLUSIONS

Although the feasibility and success of the use of muscle oximetry in sports science is well documented, there is still a need for further instrumental development to overcome current instrumental limitations. Longitudinal studies are urgently needed to strengthen the benefits of using muscle oximetry in sports science.

Photobiomodulation does not improve anaerobic performance in well-trained cyclists

To determine if photobiomodulation (PBM) has ergogenic effects on the anaerobic performance of well-trained cyclists. Fifteen healthy male road or mountain bike cyclists participated in this randomized, double-blinded, placebo-controlled, crossover study. Athletes were randomly assigned to receive photobiomodulation (630 nm, 4.6 J/cm², 6 J per point, 16 points, PBM session) or placebo intervention (PLA session) in the first session. The athletes then performed a 30-s Wingate test to determine mean and peak average power, relative power, mean and peak velocity, mean and peak RPM, fatigue index, total distance, time to peak power, explosive strength, and power drop. After 48 h, athletes returned to the laboratory for the crossover intervention. The repeated-measures ANOVA test followed by Bonferroni post hoc test or Friedman test with Dunn's post hoc test (p < 0.05), and Cohen's d statistic were used for comparisons. Performance in the Wingate test was not significantly different (p > 0.05) between PBM and PLA sessions for any variable. Only a small effect size was detected for time to peak power (-0.40; 1.11 to 0.31) and explosive strength (0.38; -0.34 to 1.09). We conclude that irradiation with red light, under a low energy density, does not promote ergogenic effects on the anaerobic performance of cycling athletes.

Effects of Active Preconditioning With Local and Systemic Hypoxia on Submaximal Cycling

PURPOSE

The authors compared the effects of active preconditioning with local and systemic hypoxia during submaximal cycling.

METHODS

On separate visits, 14 active participants completed 4 trials. Each visit was composed of 1 preconditioning phase followed, after 40 minutes of rest, by 3 × 6-minute cycling bouts (intensity = 85% of critical power; rest = 6 min). The preconditioning phase consisted of 4 × 5-minute cycling bouts at 1.5 W·kg-1 (rest = 5 min) in 4 conditions: control (no occlusion and normoxia), blood flow restriction (60% of total occlusion), HYP (systemic hypoxia; inspired fraction of oxygen = 13.6%), and blood flow restriction + HYP (local and systemic hypoxia combined).

RESULTS

During the preconditioning phase, there were main effects of both systemic (all P < .014) and local hypoxia (all P ≤ .001) on heart rate, arterial oxygen saturation, leg discomfort, difficulty of breathing, and blood lactate concentration. Cardiorespiratory variables, gross efficiency, energy cost, and energy expenditure during the last minute of 6-minute cycling bouts did not differ between conditions (all P > .105).

CONCLUSION

Local and systemic hypoxic stimuli, or a combination of both, during active preconditioning did not improve physiological responses such as cycling efficiency during subsequent submaximal cycling.

Blood Flow Restriction Training Can Improve Peak Torque Strength in Chronic Atrophic Postoperative Quadriceps and Hamstrings Muscles

PURPOSE

To report a prospective study of patients who underwent blood flow restriction training (BFRT) for marked quadriceps or hamstring muscle deficits after failure to respond to traditional rehabilitation after knee surgery.

METHODS

The BFRT protocol consisted of 4 low resistance exercises (30% of 1 repetition maximum): leg press, knee extension, mini-squats, and hamstring curls with 60% to 80% limb arterial occlusion pressure. Knee peak isometric muscle torque (60° flexion) was measured on an isokinetic dynamometer.

RESULTS

Twenty-seven patients (18 females, 9 males; mean age, 40.1 years) with severe quadriceps and/or hamstrings deficits were enrolled from April 2017 to January 2020. They had undergone a mean of 5.3 ± 3.5 months of outpatient therapy and 22 ± 10 supervised therapy visits and did not respond to traditional rehabilitation. Prior surgery included anterior cruciate ligament reconstruction, partial or total knee replacements, meniscus repairs, and others. All patients completed 9 BFRT sessions, and 14 patients completed 18 sessions. The mean quadriceps and hamstrings torque deficits before BFRT were 43% ± 16% and 38% ± 14%, respectively. After 9 BFRT sessions, statistically significant improvements were found in muscle peak torque deficits for the quadriceps (P = .003) and hamstring (P = .02), with continued improvements after 18 sessions (P = .004 and P = .002, respectively). After 18 BFRT sessions, the peak quadriceps and hamstring peak torques increased > 20% in 86% and 76% of the patients, respectively. The failure rate of achieving this improvement in peak quadriceps and hamstring torque after 18 BFRT sessions was 14% and 24%, respectively.

CONCLUSIONS

BFRT produced statistically significant improvements in peak quadriceps and hamstring torque measurements after 9 and 18 sessions in a majority of patients with severe quadriceps and hamstring strength deficits that had failed to respond to many months of standard and monitored postoperative rehabilitation.

LEVEL OF EVIDENCE

Level IV therapeutic case series.

Cardiac autonomic recovery following traditional and augmented remote ischemic preconditioning

PURPOSE

While the possible ergogenic benefits of remote ischemic preconditioning (RIPC) make it an attractive training modality, the mechanisms of action remain unclear. Alterations in neural tone have been demonstrated in conjunction with circulatory occlusion, yet investigation of the autonomic nervous system following RIPC treatment has received little attention. We sought to characterize alterations in autonomic balance to both RIPC and augmented RIPC (RIPC_aug) performed while cycling, using acute and sustained autonomic indices.

METHODS

Thirteen participants (8M:5F) recorded baseline waking heart rate variability (HRV) for 5 days prior to treatment. Participants then completed control exercise (CON), RIPC, and RIPC_aug interventions in a randomized cross-over design. Cardiovascular measurements were recorded immediately before and after each intervention at rest, and during an orthostatic challenge. Waking HRV was repeated the morning after each intervention.

RESULTS

RIPC resulted in acutely reduced resting heart rates (HR) (∆ - 4 ± 6 bpm, P = 0.02) and suppressed HR 30 s following the orthostatic challenge compared to CON (64 ± 10 vs 74 ± 9 bpm, P = 0.003). RIPC_aug yielded elevated HRs compared to CON and RIPC prior to (P = 0.003) and during the orthostatic challenge (P = 0.002). RIPC_aug reduced LnSDNN (Baseline 4.39 ± 0.27; CON 4.44 ± 0.39; RIPC 4.41 ± 0.34; RIPC_aug 4.22 ± 0.29, P = 0.02) and LnHfa power (Baseline 7.82 ± 0.54; CON 7.73 ± 1.11; RIPC 7.89 ± 0.78; RIPC_aug 7.23 ± 0.87, P = 0.04) the morning after treatment compared to all other conditions.

CONCLUSIONS

Our data suggest that RIPC may influence HR acutely, possibly through a reduction in cardiac sympathetic activity, and that RIPC_aug reduces HRV through cardiac vagal withdrawal or increased cardiac sympathetic modulation, with alterations persisting until the following morning. These findings imply a dose-response relationship with potential for optimization of performance.

Effects on performance of active and passive hypoxia as a re-warm-up routine before a 100-metre swimming time trial: a randomized crossover study

Passive and active hypoxia could be used as a tool during a transitional phase to maintain the effects of warm-up and optimize athletic performance. Our purpose was to evaluate and compare the effects of four different re-warm-up strategies, i.e. rest in normoxia (RN) at FiO₂ = 20.9%, rest in hypoxia (RH) at FiO₂ = 15%, active (5 minutes dryland-based exercise circuit) in normoxia (AN) and active in hypoxia (AH), during the transitional phase, on subsequent 100 m maximal swimming performance. Thirteen competitive swimmers (n = 7 males; n = 6 females; age: 15.1±2.1 years; height: 164.7±8.8 cm; weight: 58.1±9.7 kg; 100 m season’s best time 72.0±11.8 s) completed a 20-minute standardized in-water warm-up followed by a 30-minute randomized transitional phase and 100 m freestyle time trial. Compared to AH (73.4±6.2 s), 100 m swim time trials were significantly (p = 0.002; η² = 0.766) slower in RN (75.7±6.7 s; p = 0.01), AN (75.2±6.7 s; p = 0.038) and RH (75.0±6.4 s; p = 0.009). Moreover, compared to AH (36.3±0.4ºC), tympanic temperature was significantly lower (p<0.001; η² = 0.828) at the end of the transitional phase in passive conditions (RN: 35.9±0.6; p = 0.032; RH: 36.0±0.4; p = 0.05). In addition, countermovement jump height at the end of the transitional phase was significantly higher in active than in passive conditions (p = 0.001; ^η2 = 0.728). A dryland-based circuit under hypoxia could be useful to swimmers, once it has attenuated the decline in tympanic temperature during a 30-minute transitional phase after warm-up, improving 100 m swimming performance in young amateur swimmers.

An Updated Panorama of "Living Low-Training High" Altitude/Hypoxic Methods

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.