Serum creatine kinase activity following forearm flexion isometric exercise

Summary The purpose of this study was to 1) compare serum creatine kinase (CK) activity following two forearm flexion isometric exercise regimens differing in work to rest ratio, and 2) examine the CK response to a repeated bout of isometric exercise. Eleven males were tested on two sessions (bouts) spaced 1 week apart. For bout 1, five subjects (group A) performed a forearm flexion isometric exercise consisting of 40 10-s maximal contractions with 20-s inter-trial rests (1020), while six (group B) performed 40 maximal 10-s contractions with 5-s inter-trial rests (105). The increase in serum CK activity following the 1020 exercise (143%) was significantly greater than that following the 105 exercise (52%). The 1020 exercise was also associated with greater tension generation over trials. One week later, both groups performed a bout of 1020 exercise. A substantial reduction in the serum CK response was found following this second bout. The data suggest that for bout 1 the isometric exercise associated with the greater overall tension levels resulted in the greater CK response. However, when the 1020 exercise was repeated 1 week later, a substantial reduction in the CK response was found which was unrelated to the tension generated.This study was supported by a University Faculty Research Grant No. 2-03021     

Blood coagulation and fibrinolysis after long-duration treadmill exercise controlled by individual anaerobic threshold

For rehabilitation training it is recommended that the intensity of exercise should be clearly below the individual anaerobic threshold (IAT). We investigated blood coagulation, particularly endogenous thrombin potential (ETP) and fibrinolysis following a standardized treadmill (TR) ergometer test at 90% IAT for 60–120 min. Sixteen healthy male non-smokers underwent the TR test. Blood samples were taken after a 30-min rest, immediately after exercise, and 2 h after exercise completion. Extrinsic and intrinsic total (TTP_ex+in) and endogenous (ETP_ex+in) thrombin potential, prothrombin fragment 1+2 (F1+2), thrombin-antithrombin complex (TAT), plasmin-2-antiplasmin complex (PAP), D-dimer, tissue plasminogen activator antigen and activity (tPA-AG and tPA-ACT) and plasminogen activator inhibitor type 1 antigen and activity (PAI-1-AG and PAI-1-ACT) were measured. Immediately after TR, F1+2, TAT and TTP_ex+in were increased (P<0.05) while ETP_ex+in remained unchanged. In contrast, PAP, D-dimer, tPA-AG, tPA-ACT (P<0.05) were distinctly enhanced while PAI-1-ACT was decreased (P<0.05) immediately after exercise. The changes in tPA-AG, tPA-ACT, and PAI-1-ACT were reversed to nearly baseline while the enhancement in PAP and D-dimer was prolonged by more than 2 h after exercise. Long-duration exercise between 60 and 120 min controlled by IAT (90%) on a TR ergometer only implicates a small increase in thrombin generation markers and total (free and ₂-macroglubulin-bound thrombin), but not in endogenous (free) thrombin potential alone. In contrast, fibrinolysis is distinctly increased after this type of exercise. Endurance exercise with an intensity below 90% IAT and a duration below 2 h generates a more favourable condition for fibrinolysis than for blood coagulation in healthy young subjects. Data are given as mean (SD).     

Effect of endurance and sprint exercise on the sensitivity of glucose metabolism to insulin in the epitrochlearis muscle of sedentary and trained rats

Summary The effects of two types of acute exercise (1 h treadmill running at 20 m· min^–1, or 6 × 10-s periods at 43 m · min^–1, 0° inclination), as well as two training regimes (endurance and sprint) on the sensitivity of epitrochlearis muscle [fast twitch (FT) fibres] to insulin were measured in vitro in rats. The hormone concentration in the incubation medium producing the half maximal stimulation of lactate (la) production and glycogen synthesis was determined and used as an index of the muscle insulin sensitivity. A single period of moderate endurance as well as the sprint-type exercise increased the sensitivity of la production to insulin although the rate of la production enhanced markedly only after sprint exercise at 10 and 100 U· ml^–1 of insulin. These effects persisted for up to 2 h after the termination of exercise. Both types of exercise significantly decreased the muscle glycogen content, causing a moderate enhancement in the insulin-stimulated rates of glycogen synthesis in vitro for up to 2 h after exercise. However, a significant increase in the sensitivity of this process to insulin was found only in the muscle removed 0.25 h after the sprint effort. Training of the sprint and endurance types increased insulin-stimulated rates of glycolysis 24 h after the last period of exercise. The sensitivity of this process to insulin was also increased at this instant. Both types of training increased the basal and maximal rates of glycogen snythesis, as well as the sensitivity of this process to insulin at the 24^th following the last training session. It was concluded that in the epitrochlearis muscle, containing mainly FT fibres, both moderate and intensive exercise (acute and repeated) were effective in increasing sensitivity of glucose utilization to insulin. Thus, the response in this muscle type to increased physical activity differs from that reported previously in the soleus muscle, representing the slow-twitch, oxidative fibres in which sprint exercise did not produce any changes in the muscle insulin sensitivity.     

Effect of submaximal exercise at low temperatures on pulmonary function in healthy young men

Summary In order to understand more fully the effect on pulmonary function of whole body exposure to cold during submaximal exercise, we measured pulmonary function indices in ten healthy male students and ten healthy male forestry workers of similar age following submaximal treadmill walking at different temperatures in a climatic chamber. After measuring the maximal aerobic capacity with a cycle ergometer test, the subjects had to walk on four separate occasions in the climatic chamber at an intensity of 70%–75% of their individual maximal heart rate; the first at normal room temperature and then randomly, either at 0°C or at −20°C, and vice versa. The duration of each walk was 8 min. Finally, each subject had to walk in the chamber at −20° C for 17 min. Flow volume spirometry was performed at room temperature 1, 5, 10, and 20 min after exercise and the values were compared to baseline values taken prior to the last walking test. There were only minor changes in pulmonary function indices following exercise at different temperatures. Only one student showed a reduction of over 15% in peak expiratory flow rate after an 8-min walk at −20° C. It seems that submaximal exercise of short duration, even at a temperature as low as −20° C, does not impair pulmonary function in healthy young men.     

Residual effects of prior exercise and recovery on subsequent exercise-induced metabolic responses

Abstract Data on the metabolic responses to repeated endurance exercise sessions are limited. Thus, the aims of this study were to examine (1) the impact of prior exercise on metabolic responses to a subsequent exercise session and (2) the effect of different recovery periods between two daily exercise sessions on metabolic responses to the second bout of exercise. Nine male elite athletes participated in four 25-h trials: one bout of exercise (ONE), two bouts of exercise separated by 3 h of rest and one meal (SHORT), two bouts of exercise separated by 6 h of rest and two meals (LONG), and a trial with no exercise (REST). All exercise bouts consisted of 10 min cycling at 50% followed by 65 min at 75% of maximal O₂ uptake. Compared to no prior exercise (ONE), a previous bout of exercise (SHORT) was followed by higher mean O₂ uptake, heart rate (HR), rectal temperature (T_R), excess post-exercise oxygen consumption and lower respiratory exchange ratio (R) during and after a similar exercise session 3 h later. A longer rest interval between the two exercise bouts (6 h versus 3 h) and an additional meal resulted in a decrease in O₂ uptake, HR, T_R and an increase in R during the second bout of exercise, but no effects on post-exercise metabolism were found. Thus, augmented metabolic stress was observed when strenuous exercise was repeated after only 3 h of recovery, but this was attenuated when a longer recovery period including an additional meal was provided between the exercise sessions.     

Exercise motivation and adherence in cancer survivors after participation in a randomized controlled trial: An attribution theory perspective

The purpose of this study was to examine postprogram exercise motivation and adherence in cancer survivors who participated in the Group Psychotherapy and Home-Based Physical Exercise (GROUP-HOPE; Courneya, Friedenreich, Sela, Quinney, & Rhodes, 2002) trial. At the completion of the GROUP-HOPE trial, 46 of 51 (90%) participants in the exercise group completed measures of attribution theory constructs. A5-week follow-up self-report of exercise wasthen completed by 30 (65%) participants. Correlational analyses indicated that program exercise, perceived success, expected success, and affective reactions were strong predictors of postprogram exercise. In multivariate stepwise regression analyses, program exercise and perceived successwere the strongest predictors of postprogram exercise. Additionally, perceived success was more important than objective success in understanding the attribution process, and it interacted with personal control to influence expected success and negative affect. Finally, postprogram quality of life and changes in physical fitness were correlates of perceived success. We concluded that attribution theory may have utility for understanding postprogram exercise motivation and adherence in cancer survivors.     

Red cell hemoglobin,hydrogen ion and electrolyte concentrations during exercise in trained and untrained subjects

Summary Red cell concentrations of hemoglobin (MCHC), H⁺, Na⁺, K⁺, Mg⁺⁺, Cl^– were measured in femoral venous blood of six untrained (UT), six endurance trained (TR) and three semitrained (ST) subjects during graded increasing work (4, 8, 12, 18 and 24 mkp/s, 10–15 min on each step) on a bicycle ergometer. Before exercise no significant differences were detected for the measured variables when comparing UT and TR. During exercise MCHC, [Na⁺], [K⁺] and [Mg⁺⁺] remained constant indicating lack of water shift into the erythrocytes in spite of a marked acidosis (lowest pH_Blood value 7.225). This lack resulted from an elevated extracellular osmolality. [H⁺]_Ery and [Cl^–]_Ery maximally increased by 2.0×10^–8 eq/kg H₂O and 10 meq/l, respectively. The change was markedly greater in UT than in TR at equal load. However, if [H⁺]_Ery and [Cl^–]_Ery were related to pH of whole blood, differences between groups almost disappeared and the ions were distributed as predictable from in vitro experiments (Fitzsimmons and Sendroy, 1961). Behaviour of H⁺ and Cl^– may be of importance for oxygen dissociation under in vivo conditions.Supported by Bundesinstitut für Sportwissenschaften, Köln     

CO2 dissociation curves of oxygenated whole blood obtained at rest and in exercise

Summary In vitro CO₂ dissociation curves for oxygenated whole blood were determined in 19 healthy male subjects at rest and during submaximal and maximal bicycle work. Hemoglobin concentration and blood lactate increased with increasing work load and accordingly buffer value of the whole blood increased while bicarbonate and Base Excess (BE) decreased, resulting in a downward shift of the CO₂ dissociation curve during exercise. Despite the marked increase in buffer values of the blood, the slopes of the CO₂ dissociation curves during exercise were found to be about the same as those obtained at rest. It was inferred that the increasing effect of increased buffer value, on the dissociation slope, was essentially compensated by the decreasing effect of diminished bicarbonate content. The advantages of this relatively constant CO₂ dissociation slope for the indirect measurement of cardiac output by the Fick principle are discussed.     

Supra-maximal cycling efficiency assessed in humans by using a new protocol

This study proposed a non-invasive method to determine the gross (GE, no baseline correction), net (NE, resting metabolism as the baseline correction) and work (WE, unloaded cycling as the baseline correction) efficiencies during cycling at an intensity higher than the maximal aerobic power (MAP). Twelve male subjects performed two exercises consisting of 4 min at 50% MAP followed either by 8 min at 63% MAP or by 8 sequences of 60 s divided into 10 s at 130% MAP and 50 s at 50% MAP (i.e., 63% MAP on average). Oxygen uptake was continuously measured to calculate GE, NE and WE at 50%, 63% and 130% MAP, and the data presented as the means and standard deviations. The GE values were 18.2%, 19.1%, 22.7%, the NE values were 22.4%, 22.8%, 24.3% and the WE values were 34.2%, 31.4% and 27.2% at 50%, 63% and 130% MAP, respectively. The GE and NE increased (P<0.001) whereas the WE decreased (P<0.001) with each increment in power output. The GE was lower than the NE (P<0.001) at 50% and 63% MAP and than the WE (P<0.001) at all intensities. The NE was lower (P<0.001) than the WE at 50% and 63% MAP. These results showed that (1) efficiency index values obtained during supra-maximal exercise were consistent with previous proposals and (2) the efficiency-power output relationships were not limited to sub-maximal intensity levels but were confirmed at higher power output.     

Skin vascular response in the hand during sinusoidal exercise in physically trained subjects

The effect of physical training on the cutaneous vascular response during transient exercise load is unclear. We determined the phase response and amplitude response of cutaneous vascular conductance (CVC) in the hand during sinusoidal exercise in endurance exercise-trained and untrained subjects. Subjects exercised on a cycle ergometer with a sinusoidal load for 32 min. The load variation ranged from 10% [23 (1) W in the trained group, 19 (1) W in the untrained group] to 60% [137 (4) W, 114 (6) W] of peak O₂ uptake, and five different time periods (1, 2, 4, 8, and 16 min) were selected. Skin blood flow in the dorsal hand and palm were monitored by laser-Doppler flowmetry. CVC was evaluated from the ratio of blood flow to mean arterial pressure. During sinusoidal exercise, the amplitude of CVC was smaller in the dorsal hand than palm for shorter periods (1, 2, and 4 min) (P<0.05). The phase lag of CVC was smaller in the dorsal hand than palm for longer periods (8 and 16 min) (P<0.05). The amplitude response did not differ significantly between the two groups. The phase lag of CVC in the dorsal hand (P<0.05) and palm (P=0.06) was larger in the trained group than untrained group. These findings suggest that glabrous and nonglabrous skin vascular responses in the hand differ during transient exercise load, and physically trained subjects show a slower vascular response in the two skin areas to exercise stimulation than do untrained subjects.