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Blood flow restriction as a method to elicit post activation potentiation in trained female athletes

It is essential within the sporting context to be able to physically perform at the highest level possible. This demands training methods and tools that can enhance strength and power both chronically and acutely to ensure performance is maximised. Post activation potentiation (PAP) is a method that acutely enhances muscular force output and performance through performing a potentiating stimulus. While PAP has been shown to be effective in certain situations, any acute performance effects are known to be the summation of the potentiating effects and any accumulated fatigue. Blood flow restriction (BFR) is a training modality that has been shown to be effective in enhancing muscle size and strength via occlusion of the arterial flow which may enable the recruitment of high threshold motor units, create a high metabolic stress, and lead to muscular environment suited to adaptation. These physiological effects, combined with a low level of central fatigue, may combine to provide a situation where PAP is achieved. To date, only one study has investigated the effects of using BFR as a potentiation tool, and no research has been performed on female participants. This thesis starts by evaluating and synthesizing the existing literature regarding both PAP and BFR training illustrating that there are a variety of performance benefits of using both PAP and BFR (Chapter One). Of the studies identified, 76% showed high intensity-low volume resistance exercise to be effective in inducing PAP, 86% showed WBV training to be effective, and 83% showed ‘other’ methods to be effective. Overall, 10 of the 42 studies identified (29%) were unsuccessful at eliciting PAP. The literature also suggests that a higher methodological quality of training characteristics, especially relating to the inclusion of female participants, is crucial to ensure the most efficient approach to using BFR to induce PAP. Specifically, of the 42 studies identified that assessed the effects of lower body PAP on sprint and jump performance in athletes, only two studies (4.8%) were conducted in female-only cohorts, and none of them reported details of the menstrual phase (Chapter One). Chapter Two of this thesis examined the inter-session reliability of both vertical and horizontal explosive power in trained female athletes over a 3-day period utilised in the subsequent experimental chapter to inform the typical error of measurement. The reliability sessions assessed the components of the force-velocity profile for horizontal (20-m running sprint) and vertical (squat jump at body weight, 24 kg, and 48 kg), as well as power using an OptoJumpᵀᴹ and a StalkerATS Radar Gun. Intraclass correlation coefficients (ICC), typical error (TE) and coefficient of variation (CV) with 95% confidence intervals were calculated to compute relative and absolute reliability of measures. The force-velocity component metrics that exhibited acceptable reliability included V0ᵥₑᵣₜ [CV:5.2%, ICC: 0.81 (good)], F0ᵥₑᵣₜ [CV: 6.2%, ICC: 0.7 (good)], and power Pmaxᵥₑᵣₜ [CV: 3.6%, ICC: 0.89 (good)]; while velocity V0ₕₒᵣᵢ₂) exhibited a reliable CV of 9.8%. The performance metrics exhibited acceptable reliability for BW [CV: 6.9%, ICC: 0.91 (good)] with a low typical error (1.5 cm). When compared to BW jump height measures, sprint speed presented having acceptable reliability [CV: 5.5%, ICC: 0.73 (good)], however, the typical error (1.1 km/h) can be considered large. The reliability results for 24 kg weighted jump exhibited a CV slightly over acceptable range [CV: 10.2%, ICC: 0.84 (good)]; while the data collected for 48 kg weighted jump showed acceptable ICC results, but a poor CV [CV: 36.2%, ICC: 0.84 (good)]. The correlation data demonstrated that Pmaxᵥₑᵣₜ was very strongly correlated with jump performance (r = 0.97), but the association with F0ᵥₑᵣₜ was weak (r = 0.22). In contrast, both Pmaxₕₒᵣᵢ₂ (r = 0.71) and F0ₕₒᵣᵢ₂ (r = 0.65), were strongly related to sprint speed. Pmaxᵥₑᵣₜ was very strongly related to sprint speed (r =0.83). Additionally, there was a strong relationship between Pmaxᵥₑᵣₜ and Pmaxₕₒᵣᵢ₂ (r = 0.63), but the relationships between the corresponding horizontal and vertical F0 and V0 were weak. There was no indication that high levels of theoretical maximal force (F0ₕₒᵣᵢ₂ or F0ᵥₑᵣₜ) were related to a greater potentiation response. The penultimate chapter (Chapter Three) investigated the effects of using BFR to elicit PAP in well-trained female athletes. The athletes completed the testing protocols a minimum of 2-days apart and running sprint and squat jump were assessed 4 and 8-min post the PAP intervention. The PAP intervention included completing four sets of bodyweight squats (30, 15, 15, 15 repetitions separated by 30 second rest intervals) with occlusion cuffs applied to the proximal region of the thigh inflated to 180 mmHg; whereas, the control intervention performed the same stimulus without occlusion. With the potentiating stimulus being vertically oriented, we hypothesised that this intervention would be more effective in jumping than sprinting. A 2-way (group x time) repeated-measure ANOVA used to analyse jump performance showed a negative effect of time in bodyweight (p= 1.01x10⁻⁷ ) and 24 kg jump (p= 2.97x10⁻⁶) conditions. An interaction effect was observed in the bodyweight jump (p = 0.0436), and post hoc analyses showed that the decrease in jump height was greater in the CON condition. Thus, while there was no evidence of potentiation in the body weight squat jump, there was a small significant difference in the decrease observed from Pre to Post 4 (p=0.0409) with a large effect size (ES=1.01) indicating that there was less fatigue between Pre and Post 4 for the BFR condition compared to the CON condition. The repeated-measures ANOVA used to analyse sprint potentiation reported no evidence of potentiation in sprint performance at any time point after the conditioning stimulus, results were considered unclear (Post 4: d = 0.22 ±0.42) or trivial (Post 8: d= -0.16 ±0.24). Overall, the results did not show any significant differences in performance between the two conditions. Therefore, concluding that the BFR protocol used in this study failed to elicit potentiation in female athletes. The literature suggests that when there is an optimal balance between potentiation and fatigue it can be utilised to improve performance and low resistance exercise combined with blood flow restriction has been shown to successfully improve performance in males. However, there is very a limited amount of research done using 6 blood flow restriction in females. Hence, the aim of this thesis was to unpack the literature regarding post activation potentiation and blood flow restriction and use it to guide our study in an attempt to potentiate an improvement in jump and sprint performance using BFR in trained females.
Type of thesis
The University of Waikato
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