This study investigated the effects of ungraded running and graded walking as modalities of HIIT on enjoyment, perceived exertion, and affect. 29 healthy males and females (aged 23.3 ± 5.1) volunteered to participate in the study. Participants completed six visits to the laboratory: the first was a medical screening to ensure safety of the participants. For the second and third visits, participants completed two maximal treadmill exercise tests, one running and one walking. On the fourth visit, the speed needed for the run HIIT (running speed: 6.9 ± 1.2mph) and the grade needed for the walk HIIT (walking speed: 3.3 ± 0.3mph, walking grade: 17.2 ± 3.1%) experimental trials were confirmed. During the last two visits, participants completed both of the two (run HIIT and walk HIIT) randomized and counterbalanced experimental trials. Affective valence was measured at baseline and post-exercise. The single-item Feeling Scale (FS) and the Borg 6-20 RPE scale (both overall exertion and legs-only exertion) were used to measure in-task ratings of affect and exertion. The Physical Activity Enjoyment Scale (PACES) and FS were used to measure post-exercise ratings of enjoyment and affect. Results revealed a main effect for condition for post-exercise enjoyment (p < 0.001), with the run HIIT being more enjoyable. A main effect was also found for time for both overall exertion and legs-only exertion (p < 0.001 for both interactions), with the walk HIIT producing higher exertion ratings. There was a main effect for condition of legs-only exertion (p = 0.004), again walk HIIT produced higher exertion ratings. Lastly, there was a main effect when comparing 20% and 100% of total time in the run HIIT and the walk HIIT conditions, for both overall exertion and legs-only exertion (p < 0.001 for all interactions). This shows that exertion increased over time for both conditions. Exertion ratings, both overall and legs-only tended to be highest during the run HIIT condition when compared to the walk HIIT. The opposite was true for affective valence, the ratings were higher in the run HIIT condition than the walk HIIT. In conclusion, the perceptual responses in this study, which represent enjoyment, exertion and affective valence, were generally more favorable during the run HIIT condition. These results support previous findings to suggest that doing a running protocol is a well-tolerated and favorable modality for HIIT exercise.

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<p>This thesis investigated the acute and chronic responses of human skeletal muscle to high-intensity exercise, with a particular focus on markers of mitochondrial content, and the potential for nutrition to manipulate the adaptive response in recreationally active individuals. The acute response was primarily assessed via measurement of signalling proteins and mRNA species linked to exercise-induced mitochondrial biogenesis. The chronic response was determined via changes in the protein content or maximal activities of mitochondrial enzymes after training. Study 1 examined whether the manner in which a given amount of high-intensity cycling work was performed (i.e., in an intermittent or continuous fashion) altered the acute metabolic response to exercise, and whether the acute response was indicative of longer-term adaptations. Despite the similar acute activation of signalling proteins after the intermittent and continuous matched-work exercise protocols, 6 wk of training with the continuous protocol did not increase mitochondrial content, contrary to what we have previously shown after 6 wk training with the intermittent protocol. This suggests that the intermittent application of a low-volume, high-intensity stimulus is important to elicit training-induced increases in mitochondrial content. Furthermore, Study 1 showed that acute changes in specific signalling proteins did not necessarily predict chronic adaptations. Studies 2 and 3 examined whether specific nutritional interventions, previously shown to modulate acute exercise capacity or metabolic response, altered the mitochondrial adaptive response to several weeks of HIT. Neither manipulating carbohydrate availability between twice daily training sessions, or chronic ingestion of β-alanine, augmented skeletal muscle adaptations in response to 2-6 wk of HIT. It is possible that small influences of nutrition were overwhelmed by the potency of HIT, which stimulated marked increases in mitochondrial content in this population. Overall this thesis advances our basic understanding of the skeletal muscle adaptive response to HIT and the influence of nutrition.</p> / Doctor of Philosophy (PhD)

<p>This thesis examined the effect of high-intensity "sprint" interval training (SIT) on aerobic-based exercise performance and metabolic adaptations in human skeletal muscle. It has long been recognized that several weeks of interval-based training increased skeletal muscle oxidative capacity; however, little was known regarding the minimum "dose" of SIT necessary to elicit this adaptive response or the time-course and magnitude of adaptation in other markers of skeletal muscle metabolic control. Our general hypothesis was that low-volume SIT would induce rapid improvements in a wide array of metabolic variables that were comparable to traditional high-volume endurance training (ET). Healthy young men and women were recruited to perform four to six 30- second "all out" Wingate Tests, three times per week with one to two days of recovery, for up to six weeks. The weekly dose of SIT corresponded to ~10 minutes of maximal cycling exercise (-225-300 kJ) over a total training time commitment of 60-90 minutes, including recovery. The SIT response was compared against control subjects who performed no training or an ET group who performed up to one hour per day of moderate-intensity cycling exercise, five days per week for six weeks (-2250 kJ per week). Our major findings were that one to two weeks of SIT increased performance during aerobic-based exercise (time-to-fatigue tests and time-trials of varying duration) and the maximal activity or total protein content of mitochondrial enzymes and transport proteins associated with carbohydrate metabolism (e.g., citrate synthase, cytochrome oxidase, glucose transporter 4). Six weeks of SIT or ET induced similar increases in markers of skeletal muscle carbohydrate (pyruvate dehydrogenase E1a protein content) and lipid oxidation (3-hydroxyacyl CoA dehydrogenase maximal activity) and peroxisome-proliferator-activated receptorgamma coactivator-1a protein content, and similar reductions in phosphocreatine and glycogen utilization during matched-work exercise. These data suggest that SIT is a time-efficient strategy to increase skeletal muscle oxidative capacity and to induce specific metabolic adaptations during exercise that are comparable to ET.</p> / Doctor of Philosophy (PhD)

<p>Research in this thesis has focused on development and application of novel methodologies that enhance sample throughput and data fidelity when performing untargeted metabolome profiling by multisegment injection-capillary electrophoresis-mass spectrometry (MSI-CE-MS). Metabolomics is a valuable tool in functional genomics research to investigate underlying molecular mechanisms associated with human health since metabolites are “real-world” end-products of gene expression. CE-MS is well-suited for metabolomics because it is a high efficiency microseparation technique that can be used to resolve complex mixtures of polar metabolites in human biofluids without complicated sample workup. In this thesis, a novel CE-MS assay for estrogens and their intact ionic conjugates has been described (<em>Chapter II</em>) to expand metabolome coverage that enables resolution of positional isomers with high selectivity. This is critical for better understanding of underlying perturbations in estrogen metabolism since the biological activity of estrogens are dependent on specific primary and secondary metabolic transformations. MSI-CE-MS has been introduced as a high-throughput approach for large-scale metabolomic studies based on serial injection of multiple segments of sample within a single fused-silica capillary (<em>Chapter III</em>). It reduces analysis times while increasing data quality and confidence in peak assignment together with better quality assurance. An accelerated workflow for metabolomics has also been developed when using MSI-CE-MS, where a dilution trend filter is used as a primary screen to authenticate reproducible sample-derived metabolites from a pooled sample while eliminating spurious artifact and background signals. In this way, complicated time alignment and peak picking algorithms are avoided when processing data in metabolomics to reduce false discoveries. This strategy was subsequently used in two metabolomics applications (<em>Chapters IV</em> and <em>V</em>) to identify plasma markers associated with strenuous exercise and adaptive training responses following a six-week high intensity interval training. The impact of exercise intervention to improve the glucose tolerance of a cohort of overweight/obese yet non-diabetic women was investigated on an individual level when using a cross-over design. Personalized interventions are critical in designing more effective therapies to prevent metabolic diseases due to inter-subject variations in treatment responses, including potential adverse effects. MSI-CE-MS offers a revolutionary approach for biomarker discovery in metabolomics with high sample throughput and high data fidelity, which is critical for validation of safe yet effective lifestyle interventions that promote human health and reduce risk for chronic diseases.</p> / Doctor of Philosophy (PhD)

Background: Axial Spondyloarthritis (axSpA) is an autoimmune, chronic, rheumatic and inflammatory disease. In axSpA, the sacroiliac joint and the spine are affected, and common symptoms are stiffness and pain. For axSpA patients, systemic inflammation is a contributing factor to an increased risk of cardiovascular diseases (CVD). Calprotectin is a protein with multiple functions involved in the inflammatory response, and axSpA patients' calprotectin levels are elevated due to inflammation. Exercise is a non-pharmacological treatment, and for axSpA patients, it can reduce pain and increase mobility. The effects of High-intensity Interval Training (HIIT) have yet to be extensively researched in this patient group. Performing HIIT can increase maximal oxygen uptake (VO2max), reducing the risk of CVD. HIIT may also reduce inflammation, an essential factor in reducing the risk of CVD. Aim: The aim is to investigate how HIIT can affect calprotectin serum levels in axSpA patients and how calprotectin serum levels differ between healthy controls and axSpA patients. Method: Serum was collected before and after a HIIT bout from a cross-sectional pilot study, including axSpA patients (n=10) and healthy age- and sex-matched controls (n=11) and at baseline and after three months from a randomised control trial (RCT), which consisted of axSpA patients. The patients in the RCT were split into two groups: a control group (n=14) performing regular exercise and an intervention group (n=15) performing three HIIT sessions per week. Calprotectin in patients and healthy controls serum was analysed with a sandwich ELISA. Results: The comparison of serum calprotectin before and after a HIIT bout decreases in healthy controls (p=0.013) and indicates an increase of calprotectin in axSpA patients (p=0.059). After three months, the mean value of serum calprotectin in axSpA patients indicates a decrease in both the control and HIIT intervention groups. Conclusion: Our results suggest a trend towards regular HIIT, which can decrease serum calprotectin levels after three months. Therefore, HIIT could be considered a non-pharmacological treatment for axSpA patients. More studies with a larger axSpA population are necessary to investigate whether HIIT impacts serum calprotectin. / Bakgrund: Axial spondylartrit (axSpA) är en autoimmun, kronisk, reumatisk och inflammatorisk sjukdom. I axSpA påverkas sacroiliacaleden och ryggraden och vanliga symtom är stelhet och smärta. Patienter med axSpA har systemisk inflammation som är en bidragande faktor till ökad risk för hjärt-kärlsjukdomar (CVD). Kalprotektin är ett protein med flera funktioner som är involverat i den inflammatoriska responsen och hos patienter med axSpA är nivåerna av kalprotektin förhöjda på grund av inflammationen. Träning är en icke-farmakologisk behandling som kan minska smärta och öka rörlighet för axSpA patienter. Effekterna av högintensiv intervallträning (HIIT) har inte studerats i stor utsträckning i denna patientgrupp. Genom att utföra HIIT kan den maximala syreupptagningen (VO2max) förbättras, vilket kan minska risken för CVD. HIIT kan bidra till minskad inflammation, vilket kan minska risken för CVD. Syfte: Syftet är att undersöka hur HIIT kan påverka nivåerna av kalprotektin i serum hos patienter med axSpA och hur dessa nivåer skiljer sig mellan friska kontroller och patienter med axSpA. Metod: Serum har samlats in innan och efter ett HIIT pass från en tvärsnittsstudie och vid baseline och efter tre månader från en randomiserad kontrollstudie (RCT). Tvärsnittsstudien bestod av patienter med axSpA (n=10) samt friska ålders- och könsmatchade kontroller (n=11). RCTn bestod av patienter med axSpA som delades in i två grupper: en kontrollgrupp (n=14) som utförde regelbunden träning och en interventionsgrupp (n=15) som utförde tre HIIT-pass per vecka. Patienternas och de friska kontrollernas serum kalprotektin analyserades med en sandwich-ELISA. Resultat: Jämförandet av serum kalprotektin innan och efter ett HIIT pass hos friska kontroller visar en minskning av kalprotektin (p=0,013) och hos axSpA patienterna finns det en trend till en ökning av kalprotektin (p=0,059) efter HIIT-passet. Medelvärdet av serum kalprotektin hos axSpA patienter efter tre månader visar en tendens till en minskning i både kontroll- och HIIT-interventionsgruppen. Konklusion: Våra resultat indikerar att regelbunden HIIT efter tre månader kan minska nivåerna av serum kalprotektin. HIIT kan därför övervägas att vara en icke-farmakologisk behandling för axSpA patienter. Fler studier med en större axSpA population är nödvändigt för att vidare studera om HIIT påverkar serum kalprotektin.

High-intensity interval training (HIIT) consists of short intervals of exercise at high intensity intermitted by intervals of lower intensity and is associated with improvement of body composition and metabolic health in adults. Studies in overweight adolescents are scarce. We conducted a randomized controlled trial in overweight adolescents to compare acceptance and attendance of HIIT with or without weekly motivational encouragement through text messages and access to a study website. HIIT was offered for six months (including summer vacation) twice a week (60 min/session). Participation rates were continuously assessed and acceptance was measured. Clinical parameters were assessed at baseline and after six months. Twenty-eight adolescents participated in this study (age 15.5 +/- 1.4; 54% female). The standard deviation score for body mass index over all participants was 2.33 at baseline and decreased by 0.026 (95% CI - 0.048 to 0.10) units, p = 0.49. Waist to height ratio was 0.596 at baseline and decreased by 0.013 (95% CI 0.0025 to 0.024), p = 0.023. Participation within the first two months ranged from 65% to 75%, but fell to 15% within the last three months. Attendance in the intervention group was 14% (95% CI - 8 to 37), p = 0.18, higher than the control group. Overall program content was rated as \"good\" by participants, although high drop-out rates were observed. Summer months constitute a serious problem regarding attendance. The use of media support has to be assessed further in appropriately powered trials.

Training studies involving competitive runners and road cyclists have shown substantial gains in sprint and endurance performance when sessions of high-intensity interval training were added to their usual training in the competitive phase of a season. Further research has shown large performance benefits in sprint and endurance power (7 - 9%) when cyclists combined explosive single-leg jumps with cycling-specific high-intensity interval training during a competitive season. The aim of the present study was to assess the contribution of the jumps to the gains in performance in competitive cyclists in a randomized control trial.The training protocol for the control group was based on previous experimental work in which the control group (n=8) completed cycle specific interval training followed by a series of explosive single-leg jumps. The experimental group (n=7) carried out the same cycle specific interval training but did not participate in the explosive single-leg jumps. While the current study did not use a true control group, the investigation was carried out in the knowledge that a combination of high intensity interval cycling and explosive single-leg jumps causes changes positive changes in performance. Participants took part in 10 x 30-min sessions consisting four sets of high intensity intermittent cycling (4 x 30-s maximum efforts at 50 - 60 min-1 alternating with 30-s recovery). Between each set of 4 x 30 s sprints the control (ballistic) group carried out one set of explosive single-leg jumps (20 for each leg), while the experimental (continuous) group cycled for 20 s at 50 - 60 min-1.Before and after the training period all cyclists completed an incremental peak power test for assessment of VO2max, lactate threshold, exercise economy and peak power, a 30 s Wingate sprint test and a 20 km time-trial. Relative to the control group the percent mean changes (±90% confidence limits) in the experimental group were: power at 4-mM lactate, -4.2 (±6.3); VO2max, -3.1 (±3.7); mean time-trial power, -0.7 (± 4.7); peak incremental power, -1.7; (±5.0); power at 80% max heart rate, -2.8; (±5.6); Wingate peak power, -4.2; (±7.8). We conclude that high-intensity training may improve performance but the combination of high-intensity training and explosive resistance training in the competitive phase is likely to produce greater gains in trained cyclists than high intensity cycling alone.