Acute incremental endurance performance and explosive strength training period : muscle activity, acid-base balance and hormonal responses

Ville Saikko (2015). Acute incremental endurance performance and explosive strength training period: Muscle activity, acid-base balance and hormonal responses. Department of Biology of Physical Activity, University of Jyväskylä, Master’s Thesis in Exercise Physiology. 76 pp. Introduction. The acute physiological responses of human body to endurance and strength exercise occur in musculoskeletal, cardiovascular, respiratory, endocrine and immune systems. These responses can impair a performance, and for example, acid-base balance is strictly regulated in order to prevent negative outcomes. Muscle function can be examined by electromyography (EMG) and nowadays it is also possible to use textile electrodes, which allows recording of activity of muscle groups during normal locomotion. The main aims of this study was to study the associations between activity of hamstring and quadriceps muscles and acid-base balance during incremental speed running test, compare differences in muscle activation during cycling and running, and investigate the effects of additional explosive strength training on the physiological determinants of endurance performance in recreationally active persons. Furthermore, another aim was to investigate the acute responses in blood cell counts, acid-base balance and testosterone and cortisol induced by incremental speed running test. Methods. Sixteen recreationally active persons, nine women (age 22.6 ± 2.0 yr; VO2max 42.8 ± 4.1 ml/kg/min) and seven men (age 28.1 ± 10.7 yr; VO2max 50.9 ± 5.4 ml/kg/min), participated in the study. The study contained pre-, midand post-measurements and two training periods, each lasting six weeks. One period included light endurance exercises and the other speed, explosive strength and running technique exercises. During measurement day, the subjects performed an incremental running test (IRT) on an indoor running track, 20 m maximum sprint with a flying start, countermovement jumps (CMJ), and half squats. Blood samples were taken in several different time points (FAST, PRE, POST, POST30’ and POST60’). After two resting days, the subjects performed also a bicycle test (ICT). EMG shorts (Myontec Ltd.) were used during all the tests. Results. The IRT induced a significant increase in blood leukocyte count both in men (66.8%; p<.05) and in women (80.8%; p<.01) and concentration of testosterone increased significantly in men (18.4%; p<.05) during IRT. Blood pH decreased both in men and women (p<.05 and p<.01, respectively), and the change in HCO3 and BE (p<0.05 and p<.01, respectively) showed significant metabolic acidosis. The change in the activity of hamstring and quadriceps muscles correlated well with the decrease in blood pH (r=-0.61, p<.05). The results also indicated that the increase in total muscle activity during running is achieved by increasing more the activity of hamstring muscles (92.1 %) than quadriceps muscles (65.2 %). During maximal speed running, the activity of hamstring muscles was dominant (60.3 ± 5.9 %), while during maximal cycling the activity of quadriceps was higher (57.6 ± 4.1 %). Conclusions. The present study showed that increased electrical activity of hamstring and quadriceps muscles correlated well with the changes in acid-base balance in recreational active persons during the IRT. So, it seems that a greater increase in muscle activity (∆ = maximal load the first load) is needed for a bigger decrease in blood pH and BE (∆ = POST PRE), and EMG shorts are a useful method for determining this change. The results indicated also that increased total activity of thigh muscles is achieved mainly by increasing the activity of hamstring muscles during running. Activation of hamstring and quadriceps muscles during maximal running and cycling were significantly different, so this information can be beneficial for those who use both type of exercises in their training programs, such as triathletes. However, the use of special cycling shoes and pedals could have affected the activation of hamstring muscles during the ICT.