Enhancing Team Pursuit Performance using Blood Flow Restriction
The studies in this thesis investigated the physiological determinants of 4-km team-pursuit (TP) track cycling performance and critically evaluated the use of modelling finite work capacity (W′) and its dynamic balance (W′BAL) during the TP. This thesis also examined the integration of blood flow restriction (BFR) into high-intensity interval training (HIIT) as an intervention to improve factors related to TP performance. A series of related investigations were conducted with trained cyclists up to the Olympic level. Study One recruited male TP squads from International, National, and Regional performance levels. The TP squads were assessed for their critical power (CP) and W′. Maximal 4-km TP efforts confirmed different performance times of 3:49.9, 3:56.7, and 4:05.4 (minutes:s) for International, National, and Regional, respectively. Four TP simulation trials quantified W′ reconstitution from 0 to 100 W below CP. Results showed that the International squad were differentiated from National and Regional performance levels with greater CP (p < 0.05), likely preserving W′ for leading efforts. Furthermore, the International team possessed the fastest rates of W′ reconstitution at recovery intensities within 50 W of CP (p < 0.05), demonstrating the importance of W′ reconstitution at intensities near CP for recovery in the TP. The International team also expended a greater total quantity of W′ than its initial size (104 ± 5%), further demonstrating the capacity to utilise the reconstituted W′. In conclusion, we found that the TP relies on high aerobic capacity and rapid metabolic recovery abilities. An intervention was conceived based on the demands of the TP and the existing training sessions of elite TP cyclists. The training intervention included principles of TP training philosophy where cyclists repeatedly practice competition demands, at their TP lead intensity. As elite TP cyclists engage in substantial training volumes, it was important not to substantially exceed current training workloads. Based on previous BFR research with trained cyclists, an intervention integrating BFR into the recovery between TP efforts was devised. The intervention was performed on an ergometer to enable greater control over conditions and intensity. To evaluate the metabolic demands of the BFR intervention, the Study Two assessed the acute physiological responses in 11 male and female highly-trained cyclists (V̇O2PEAK 65 ± 9 mL·kg-1·minute-1). Using a within-subject design, participants performed two work- and duration-matched HIIT sessions. The HIIT consisted of six high-intensity repetitions with BFR occlusion between work bouts at 200 mmHg for 2-minutes applied proximally on the thighs (BFR) or HIIT alone without BFR (CON). Work intensity was set as 85% of the mean power output of a maximal 30-s test to simulate TP lead intensity. Cardiopulmonary variables (O2 uptake, V̇O2; carbon dioxide production V̇CO2; and ventilation, V̇E) and muscle oxygenation responses were measured during the HIIT, and vascular endothelial growth factor (VEGF) was measured pre- and 3-hours post-HIIT. Results demonstrated that BFR increased V̇CO2 and V̇E (both p < 0.05) during work bouts but did not affect V̇O2 and TSI (both p>0.05). Compared to CON, the BFR intervention significantly decreased V̇O2, V̇CO2, V̇E, and TSI during BFR occlusion (all p<0.05). Following cuff release, there were significantly higher values of V̇O2, V̇CO2, and V̇E, whereas TSI was suppressed (all p < 0.05). There were significant enhancements of serum VEGF concentration at 3-hours post-HIIT after BFR when compared to CON. As BFR appeared to delay recovery, it was hypothesised that BFR may increase metabolic and oxidative stress by delaying recovery processes. The delay in recovery may enhance the adaptations to HIIT without increasing training workload. After demonstrating that applying BFR during recovery in high-intensity work bouts increased markers of physiological stress, Study Three assessed the performance and physiological effects of the training as a chronic intervention. Using a between-subject design, ten performance-matched male trained cyclists (weekly volume >6-hours·week-1) were assigned to BFR or CON conditions. Participants performed pre- and post-intervention tests to determine lactate thresholds, 30-s maximal sprint cycling performance, and an intermittent test designed with high-intensity bouts comparable to the TP. Work bouts were performed at 85% of the mean power output of the maximal 30-s test. Muscle oxygenation and cardiopulmonary measures were continually assessed throughout the intermittent test. Participants performed four-weeks of work- and duration-matched HIIT either with 2-minutes of 200 mmHg thigh BFR between work bouts or HIIT alone (CON). Following BFR intervention, there were significant improvements in intermittent test time to exhaustion, 30-s mean power output, and submaximal lactate thresholds compared to CON (all p < 0.05). Furthermore, BFR led to significant intermittent test improvements for V̇O2PEAK and the rate of muscle tissue reoxygenation (all p < 0.05). There were no significant changes over the intervention period for CON, indicating that HIIT was ineffective in this cohort when BFR was not incorporated. Therefore, it was demonstrated that the integration of BFR between HIIT work bouts improves intermittent performance and a range of physiological factors associated with performance in trained cyclists. Finally, the BFR intervention was integrated into two HIIT sessions within a training camp of an elite TP squad preparing for the Olympic Games to test its potential efficacy and feasibility. As in the previous BFR studies, this case-study (Study Four) applied 2-minutes of 200 mmHg thigh BFR between high-intensity bouts. Work intensities were set at the individual cyclists’ TP lead intensity. A questionnaire was developed to assess the pain, tolerance, enjoyment, and compare the intervention to other training modalities. Questionnaire responses indicated that the elite cyclists enjoyed and positively perceived the intervention, appreciating the variety and efficiency of the training stimulus. All but one elite cyclist tolerated that intervention. Further investigation in conjunction with medical staff indicated that the intolerant cyclist had a pre-existing undiagnosed cardiovascular condition and presented with femoral artery claudication (discussed in the addendum). Thus, integrating BFR into HIIT for elite track cyclists was feasible and tolerable when no contraindications existed. In summary, elite TP performance relies on high sustained aerobic power output and rapid W′ recovery between efforts. This thesis showed integrating BFR between HIIT work bouts provides an additional training stimulus and can improve factors related to aerobic capacity and high-intensity intermittent performance in trained cyclists. The BFR intervention is tolerable within an elite cohort and may improve TP performance without increasing training workload.
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