Browsing by Author "Sugden, Cameron"
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- ItemThe comparison between two high-intensity interval training protocols on skeletal muscle and satellite cell dynamics(Stellenbosch : Stellenbosch University, 2019-03) Sugden, Cameron; Myburgh, Kathryn H.; Stellenbosch University. Faculty of Science. Dept. of Physiological Sciences.ENGLISH ABSTRACT: Introduction: High intensity interval training (HIIT) interventions are popularly used by endurance athletes to increase muscle strength, peak speed and aerobic capacity. Running involves the use of both eccentric and concentric contractions, with the level of the running surface determining the ratio between the two. Downhill running is considered eccentric- biased exercise. Conversely uphill running is considered concentric-biased exercise. Uphill running and downhill running are therefore two different role players in muscle adaptation, although potentially both act through regulating satellite cell (SC) dynamics. Hypothesis: The different modes of HIIT will result in differing skeletal muscle damage, satellite cell activity and morphological adaptation, resulting in differing muscle adaptation, aerobic capacity, muscle strength and running performance. Methods: 12 healthy active males were randomized into either a downhill running (DHG) or an uphill running group (UHG). Subjects underwent baseline and post training performance testing which consisted of a flat VO2max treadmill test, maximal isometric strength test and a 5km road time trial. Training consisted of 10 HIIT sessions over a period of 4 weeks. Each session consisted of 6 intervals at either +5% gradient and 80% peak treadmill speed or -10% gradient and 90% peak treadmill speed. Muscle biopsies and blood draws were taken at baseline, as well as 6 hours after the first and the last session. Results: Performance testing: The UHG, but not the DHG, improved VO2max from baseline (59.48 ± 1.73 ml.kg.min-1 – 61.86 ± 1.28 ml.kg.min-1). The DHG, but not the UHG, improved maximal isometric after the 4 weeks of HIIT (734 ± 133 N - 893 ± 55 N). Both groups improved their 5km TT performance by 3.5 ± 1%. The DHG but not the UHG had a significant increase in CK levels 6 hours after running (p < 0.05). Muscular response to 4 weeks HIIT for the DHG included an increased CSA (p < 0.05), increased SC pool size (0.1 ± 0.001 SC/fibre - 0.3 ± 0.02 SC/fibre), and an increase in myoD after the first bout of exercise (p < 0.05). Muscular adaptations in the UHG included increased capillary to fibre ratio (1.76 ± 0.18 – 2.55 ± 0.20) and capillary density (249 ± 39 mm2 – 304 ± 57 mm2) with training. Conclusion: Four weeks of uphill or downhill HIIT resulted in physiological adaptation by different mechanisms, one by enhanced SC activity and a more forceful contraction and the other involving muscle perfusion and oxygen utilization. The mechanisms of adaptation are training specific, yet they both result in a similar improvement in 5km race performance.