Turning up the heat: can post-exercise hot water immersion be used to manipulate acute physiological responses & chronic adaptation following resistance training?

Resistance training is a modality of exercise that is a staple part of strength and conditioning programmes as it offers benefits to competitive performance. Despite the positive adaptations which occur through performing regular training sessions over time, a single bout of resistance exercise results in a series of acute physiological responses. These may negatively impact performers in the hours and days post-exercise, although several questions exist with regards to appropriately characterising the magnitude and time course of this response which relate to the sensitivity of the measures which are used to do so. The context-dependent dichotomy between recovery and adaptation has fuelled much discussion in the scientific literature and has recently been articulated within the concept of hormesis, with post-exercise strategies aiming to optimise the exercise stimulus. The complex interplay between acute physiological responses and recovery/adaptation requires further investigation as recovery remains one of the least understood aspects of the exercise-adaptation cycle. Hot water immersion (HWI) is a form of heat therapy which is anecdotally reported to be used by athletes, whilst the modern advent of Jacuzzis and immersion pools in an increasing number of leisure facilities make it an easily accessible strategy. HWI may influence acute physiological responses within the recovery/adaptation paradigm but has received limited attention, while no research has investigated the chronic use of HWI alongside a resistance training programme. Therefore, the aim of this course of investigations was to elucidate the effects of HWI on acute physiological responses as well as recovery/adaptation to resistance exercise in a trained cohort. This research initially critically evaluated the literature investigating the use of HWI to identify several gaps worthy of further investigation. Subsequently, three experimental chapters were designed and conducted to assess the impact of HWI to manipulate acute physiological responses following resistance exercise and the influence on recovery/adaptation. Study 1: The aim of this investigation was to assess the usefulness of a variety of measures that are used to detail acute physiological responses following resistance exercise. The study utilised a crossover design, assessed measures through a relevant timescale (i.e. 2 h – 96 h post-exercise), recruited trained participants and employed a real-world exercise modality to enhance the ecological validity of the findings. The results suggest that several measures were able to demonstrate clear effects following resistance exercise. Additionally, the results provided a profile relating to the magnitude of change and time course for these measures with optimal sampling points identified which informed the acute physiological response measures used in subsequent chapters. Study 2: The aim of this study was to investigate the effect of HWI on acute physiological responses and recovery following resistance exercise. The main findings demonstrated that HWI is a viable means of heat therapy that can support a greater intramuscular temperature following resistance exercise. The elevated intramuscular temperature may have manipulated inflammatory processes. Although changes in other acute physiological response markers were independent of changes in intramuscular temperature associated with HWI. These results represent the first investigation into the acute physiological responses of a ‘real-world’ HWI protocol following resistance exercise, alongside the use of a trained cohort, applied exercise session and utilising good nutritional practice. Study 3: This chapter aimed to investigate the effect of HWI on acute physiological responses and training adaptation following a 10-week resistance training programme. The main findings demonstrated that HWI (i) augmented long-term gains in strength, (ii) had no effect on the post-training increase in lower body lean mass (iii) elicited an accelerated recovery of muscle function and soreness in the acute post-exercise period following training, and (iv) attenuated the increase of markers of inflammation and muscle cell disruption following training compared to passive recovery (PAS). Collectively, these findings suggest that at the end of a 10-week training programme, HWI manipulates acute physiological responses to hasten post-exercise recovery. This may have positively impacted an individual’s ability to train in subsequent sessions, leading to an accumulated training stimulus that induced small but worthwhile improvements in strength. This course of investigation has provided novel information as to how HWI manipulates acute physiological responses and the subsequent impact on recovery/adaptation following resistance exercise. In addition to identifying sensitive measures and recommended sampling points for acute physiological responses, this research provides the first evidence which suggests (i) a ‘real world’ HWI protocol can maintain an elevated intramuscular temperature and blood flow following resistance exercise, (ii) acute physiological responses can be manipulated by HWI to enhance recovery during a training programme, and (iii) the HWI-associated benefits to training enabled small but worthwhile enhancements in strength adaptations following a resistance training programme. This series of studies utilised a ‘real-world’ HWI protocol, alongside the use of a trained cohort, applied exercise session and good nutritional practice, enhancing the ecological validity of this thesis. Further work is warranted to optimise the HWI protocol and widen the scope of application to other cohorts and with different exercise modalities, as well as deepen mechanistic knowledge. However, the positive findings from this thesis provide physiologists with rationale for utilisation of HWI alongside resistance training in their applied practice

Quantification of knee extensor muscle forces: a multimodality approach

Given the growing interest of using musculoskeletal (MSK) models in a large number of clinical applications for quantifying the internal loading of the human MSK system, verification and validation of the model’s predictions, especially at the knee joint, have remained as one of the biggest challenges in the use of the models as clinical tools. This thesis proposes a methodology for more accurate quantification of knee extensor forces by exploring different experimental and modelling techniques that can be used to enhance the process of verification and validation of the knee joint model within the MSK models for transforming the models to a viable clinical tool. In this methodology, an experimental protocol was developed for simultaneous measurement of the knee joint motion, torques, external forces and muscular activation during an isolated knee extension exercise. This experimental protocol was tested on a cohort of 11 male subjects and the measurements were used to quantify knee extensor forces using two different MSK models representing a simplified model of the knee extensor mechanism and a previously-developed three-dimensional MSK model of the lower limb. The quantified knee extensor forces from the MSK models were then compared to evaluate the performance of the models for quantifying knee extensor forces. The MSK models were also used to investigate the sensitivity of the calculated knee extensor forces to key modelling parameters of the knee including the method of quantifying the knee centre of rotation and the effect of joint translation during motion. In addition, the feasibility of an emerging ultrasound-based imaging technique (shear wave elastography) for direct quantification of the physiologically-relevant musculotendon forces was investigated. The results in this thesis showed that a simplified model of the knee can be reliably used during a controlled planar activity as a computationally-fast and effective tool for hierarchical verification of the knee joint model in optimisation-based large-scale MSK models to provide more confidence in the outputs of the models. Furthermore, the calculation of knee extensor muscle forces has been found to be sensitive to knee joint translation (moving centre of rotation of the knee), highlighting the importance of this modelling parameter for quantifying physiologically-realistic knee muscle forces in the MSK models. It was also demonstrated how the movement of the knee axis of rotation during motion can be used as an intuitive tool for understanding the functional anatomy of the knee joint. Moreover, the findings in this thesis indicated that the shear wave elastography technique can be potentially used as a novel method for direct quantification of the physiologically-relevant musculotendon forces for independent validation of the predictions of musculotendon forces from the MSK models.Open Acces

Mathematical and computational models for bone tissue engineering in bioreactor systems

Research into cellular engineered bone grafts offers a promising solution to problems associated with the currently used auto- and allografts. Bioreactor systems can facilitate the development of functional cellular bone grafts by augmenting mass transport through media convection and shear flow-induced mechanical stimulation. Developing successful and reproducible protocols for growing bone tissue in vitro is dependent on tuning the bioreactor operating conditions to the specific cell type and graft design. This process, largely reliant on a trial-and-error approach, is challenging, time-consuming and expensive. Modelling can streamline the process by providing further insight into the effect of the bioreactor environment on the cell culture, and by identifying a beneficial range of operational settings to stimulate tissue production. Models can explore the impact of changing flow speeds, scaffold properties, and nutrient and growth factor concentrations. Aiming to act as an introductory reference for bone tissue engineers looking to direct their experimental work, this article presents a comprehensive framework of mathematical models on various aspects of bioreactor bone cultures and overviews modelling case studies from literature

Analysis of the backpack loading efects on the human gait

Gait is a simple activity of daily life and one of the main abilities of the human being. Often during leisure, labour and sports activities, loads are carried over (e.g. backpack) during gait. These circumstantial loads can generate instability and increase biomechanicalstress over the human tissues and systems, especially on the locomotor, balance and postural regulation systems. According to Wearing (2006), subjects that carry a transitory or intermittent load will be able to find relatively efficient solutions to compensate its effects.info:eu-repo/semantics/publishedVersio