Anita Wisén

The acute response of plasma brain-derived neurotrophic factor as a result of exercise in major depressive disorder.

Brain-derived neurotrophic factor (BDNF) and other neurotrophins are believed to play an important role in affective disorders. In this study we investigated plasma-BDNF response during an incremental exercise test in 18 patients suffering from moderate major depressive disorder (MDD) and 18 controls. The patients were not treated with antidepressants or neuroleptics. Possible associations between plasma plasma-BDNF levels, dexamethasone suppression test cortisol levels and Montgomery-Asberg Depression Rating Scale (MADRS) scores were also tested. No difference in basal BDNF levels between patients and controls was found. BDNF increased significantly during exercise in both male and female patients as well as in male controls, with no significant differences between the groups. BDNF levels declined after exercise, but after 60 min of rest BDNF levels showed tendencies to increase again in male patients. No correlation between BDNF and cortisol or MADRS scores was found. We conclude that unmedicated patients with moderate depression and normal activity of the hypothalamic-pituitary-adrenal axis do not have a disturbed peripheral BDNF release during exercise. The BDNF increase 60 min after interruption of exercise in male patients might indicate up-regulated BDNF synthesis, but this needs to be further investigated in future studies.

Repeatability of measurements of oxygen consumption, heart rate and Borg's scale in men during ergometer cycling

The coefficient of repeatability (COR), expressed as 2 SD of differences, was calculated between two measurements of oxygen consumption ( ), heart rate (HR) and rating of perceived exertion (RPE) during ergometer cycling by men. The two sets of measurements were performed 5 to 6 weeks apart. Nineteen healthy men performed an incremental maximal exercise test on an ergometer cycle. The load started at 50 W and increased by 5 W 20 s−1 until exhaustion was reached. At 40% of the individual maximum load of the pretest, the load was kept constant for 4 min in order to reach steady state. Gas measurements were recorded continuously by computerized instrumentation. The HR was monitored with electrocardiography (ECG) and the perceived exertion was evaluated using Borgs scale. The COR of at sub‐maximal load was 14% and at maximum load 11%. The values in absolute figures were 209 and 332 ml min−1. The corresponding COR of the HR was 16% at sub‐maximum load and 6% at maximum load, and an evaluation of the perceived exertion yielded CORs in absolute values of 4·8 and 1·3, respectively. The COR for , HR and ratings of perceived exertion when cycling on an ergometer cycle thus indicate a better agreement between the measurements at maximum load. The COR of the heart at sub‐maximal loads must be kept in mind when using HR for estimation of . The reported findings should be considered when using tests on an ergometer cycle for evaluating exercise capacity.

Exercise-induced release of cytokines in patients with major depressive disorder.

BACKGROUND Patients with major depressive disorder (MDD) may display elevated plasma levels of pro-inflammatory substances. Although the underlying mechanisms are unknown, inflammation has been proposed to play a direct role in the generation of depressive symptoms. Skeletal muscle is a potent producer of cytokines, and physical exercise has been suggested to alleviate symptoms of depression. In this study we therefore addressed the question of whether MDD patients display altered levels of pro-, anti-inflammatory and regulatory factors in the blood in response to acute exercise. METHODS Eighteen MDD patients and 18 healthy controls performed a maximal-workload exercise challenge. Blood samples were taken before the test, at sub-maximal and maximal workload, as well as 30 and 60 min after testing. The plasma levels of SAA, TNF-alpha, S-VCAM, S-ICAM, CRP, IFN-gamma, IL-1beta, IL-2, IL-4, IL-5, IL-6, IL-8, IL-10, IL-12 and IL-13 were assayed using multiplex sandwich ELISA. RESULTS Exercise-induced significant changes in the plasma levels of inflammatory substances in both MDD patients and controls. IL-8, IL-6 and TNF-alpha increased, and IL-4 decreased during the challenge in both groups. In addition, IFN-gamma decreased in the controls. There was a significant difference in IL-6 reactivity between the groups at the sub-max timepoint. LIMITATIONS Group sizes are comparably limited. CONCLUSION Exercise induces changes in the blood levels of cytokines in unmedicated MDD patients. Whether these changes affect symptoms of depression should be evaluated in long-term studies of the anti-depressive effects of exercise.

A refined technique for determining the respiratory gas exchange responses to anaerobic metabolism during progressive exercise – repeatability in a group of healthy men

The respiratory gas exchange and ventilation during an incremental cycle exercise test were analysed in a group of 19 healthy, moderately fit men. Different computer algorithms were used to estimate the V̇O2 values where: (i) the rate of V̇CO2 increase just exceeds the rate of V̇O2 increase (DX, derivative crossing), (ii) V̇CO2/V̇O2 = 1·00 (PX, point of crossing) and (iii) ventilation (V̇E) increases disproportionately in relation to V̇CO2 (PQ, point of V̇CO2 equivalent rise). The DX and PQ measurements were analysed using a new approach employing polynomial regression and the value of PX was determined following low‐pass filtration of raw data. The repeatability of the measurements was evaluated with a 5–6 week interval between the tests. The correlations between tests were 0·75 at DX, 0·85 at PX and 0·62 at PQ. The mean differences between the repeated tests were not statistically significant. The repeatability of V̇O2, in absolute values expressed as ±2 SD of the differences between the tests, had values of 5·0, 6·1 and 9·5 ml min−1 kg−1 for DX, PX and PQ, respectively. The mean value of V̇O2 for each measurement point expressed as a percentage of V̇O2max was 54% at DX, 68% at PX and 70% at PQ. The most common sequence of the measured values was DX < PX < PQ, but the sequence DX < PQ < PX was also observed. It is concluded that the gas exchange responses to developing anaerobic metabolism during progressive exercise can be characterized by a series of thresholds. However, the considerable variation in absolute values in the two testing occasions requires further attention.

Aerobic and functional capacity in a group of healthy women: reference values and repeatability.

Twenty‐five randomly selected, low or moderately fit and healthy women (22–44 years) rated their perceived physical capacity and performed an incremental cycle exercise test with respiratory gas analysis. The aerobic and functional capacity did not decrease with age. However, τo2 increased with age. The mean value of the perceived physical capacity was 10 metabolic equivalents and that of o2max 2075 ml min−1. The increasing anaerobic metabolism was determined at three points DX (where the rate of co2 increase just exceeds the rate of o2 increase), PX (where co2/o2 = 1·0) and PQ (where ventilation increase disproportionately in relation to co2). The mean o2 (% of o2max) at DX, PX and PQ were 1263 (63%), 1528 (73%) and 1620 (78%) ml min−1, respectively. The mean value of Δo2/ΔW was 10·2 ml min−1 W−1 while that of τo2 was 0·578 (age) + 15·6. Ten women performed a test and re‐test on two consecutive days, and eight of these performed another re‐test 4 weeks later. The repeatability was analysed and the variations were expressed as 2 SD of the differences between the tests. The variation was greater for the 4‐week re‐test than the day‐to‐day re‐test regarding o2max, o2 at DX, PX and PQ, Δo2/ΔW and HR. The variation in o2max, PX and Δo2/ΔW for the 4‐week re‐test was more than twice that of the previously reported 4‐week variation for men. The considerable variation, especially for 4‐week re‐testing for women should be considered when evaluating the effects of exercise and rehabilitation.

Comparison of heart rate measured by Polar RS400 and ECG, validity and repeatability

Abstract Aims: The purpose of this study was to investigate criterion-related validity and test–retest repeatability of the heart rate monitor Polar RS400 versus electrocardiogram (ECG). Methodology: Ten healthy subjects, 19–34 years, performed a cycle ergometer test 5 min on each load (50, 100 and 150 W). Heart rate (HR) was measured with ECG and Polar RS400 and recorded digitally. After at least one hour resting the test was repeated. Major findings: The results showed a significant correlation between HR measured by ECG and by Polar RS400 with correlation coefficients ranging from 0.97 to 1.00. In test 1 the mean difference ± 2SD between HR Polar and HR ECG was 0.7 ± 4.3 bpm and in test 2, 0.2 ± 3.2 bpm. In the repeated tests, the mean difference of HR between test 2 and test 1 ± 2SD was 3.2 ± 11.9 bpm with ECG and 2.6 ± 14.3 bpm with Polar RS400 and these differences were not statistically significant. Conclusion: This study indicates good criterion-related validity and test–retest repeatability of Polar RS400. Differences observed at individual levels should be noticed, but are not considered to be clinically important. Polar RS400 is thus well suited for recording HR during physical activity and exercise training.

The effect of different exercise intensities on health related quality of life in people classified as obese

Abstract Aims: To investigate how training intensity influences HRQoL in people classified as obese, if HRQoL changes are related to changes in weight or aerobic capacity, and to define minimal clinically important difference (MCID). Methodology: Participants (BMI ≥35 kg/m2) randomized into high-intensity training (n = 49), moderate intensity training (n = 39), or no training (n = 22), completed the SF-36 questionnaire, performed a maximal exercise test, and were weighed, before and after a 16-week intervention. Major findings: High-intensity training showed a significantly greater increase in Physical Summary Scale (PCS), Physical Functioning (PF) and General Health (GH) compared to control, and in Vitality (VT) compared to moderate intensity. Within-group analysis showed that high-intensity training improved PCS 2.0 (0.0–4.4) points (mean (95%CI)), significantly improved mental summary scale (MCS) 3.8 (1.0–6.4) points (mean (95%CI)), PF, GH, VT, mental health, aerobic capacity, and reduced body weight. Moderate intensity training significantly increased PF, GH, aerobic capacity, and reduced weight. No correlations were found between changes in HRQoL and changes in weight or changes in aerobic capacity. Conclusion: High-intensity training improved HRQoL evaluated with SF-36. HRQoL changes were not correlated with changes in weight or aerobic capacity. Proposed MCIDs are 1.3 points for PCS and 2.0 points for MCS.

Validation of a submaximal versus a maximal exercise test in obese individuals

Abstract The purpose of this study was to compare oxygen uptake estimated from submaximal Åstrand tests (VO2est) with measured peak oxygen uptake (VO2peak) from maximal tests, and to compare estimated maximal HR (HRest) with measured HRpeak in obese subjects. Seventy obese subjects performed a maximal exercise test starting with a 4-min period of constant load. VO2peak and HRpeak were measured. VO2est was based on HR at constant load. HRest was calculated by the formula 220 − age. The mean± SD of VO2est 2.05 ± 0.39 l/min (20 ± 5 ml/kg/min) was lower than VO2peak 2.42 ± 0.57 l/min (17 ± 4 ml/kg/min) (p < 0.001, p < 0.001, respectively). The mean difference ± 2SD was − 0.4 ± 1.22 l/min (− 3 ± 10 ml/kg/min) with an uneven distribution of the individual variation. The correlation between the methods was low (r = 0.24, r = 0.38 respectively). The mean± SD of HRest 176 ± 10 bpm was higher than the HRpeak 161 ± 17 bpm (p < 0.001). The mean difference ± 2SD was 15 ± 31.3 bpm with an uneven distribution of the individual variation. The correlation between the methods was low (r = 0.41). The main findings of this study were that estimation of VO2 from the Åstrand test and of HR by the formula 220 − age had low validity in obese subjects. Consequently, direct measurements of HRpeak and VO2peak are recommended for accurate prediction of obese individuals exercise capacity.

Is Ross treadmill method an alternative to Åstrand cycle ergometer method

Abstract Aims: To assess the agreement between the Ross treadmill method and the Åstrand ergometer cycle method, and the repeatability of each method. Methodology: Twenty healthy people aged 22.5 ± 2.2 years were tested on two different days, each day with both methods with a pause of 30 min between the tests. The tests were executed in the reverse order the following test day. Major findings: There was no statistical difference between the methods. The correlation (R) between the methods was 0.85. The mean difference (95% CI) of the methods was 0.050 (0.046–0.054) L/min and the limit of the agreement (mean difference ±2SD) was 0.81 L/min. No significant differences in test-retest were shown for either test. The mean difference for Åstrand tests was 0.12 L/min and 0.08 L/min for the Ross tests. The coefficient of repeatability was 0.88 L/min (23%) for the Åstrand test, and 0.78 L/min (20%) for the Ross test. Conclusion: The Ross treadmill test could be used as an alternative to the Åstrand cycle ergometer test, showing good agreement and repeatability. The large variation should be considered when estimating aerobic capacity on an individual level, although either method could be used for group studies where maximal measurements are not possible.

Effects of Acute Exercise on Circulating Soluble Form of the Urokinase Receptor in Patients With Major Depressive Disorder

Inflammation has been proposed to play a role in the generation of depressive symptoms. Previously, we demonstrated that patients with major depressive disorder (MDD) have increased plasma levels of the soluble form of the urokinase receptor (suPAR), a marker for low-grade inflammation. The aim of this study was to test the hypothesis that acute exercise would induce inflammatory response characterized by increased suPAR and elucidate whether patients with MDD display altered levels of suPAR in response to acute exercise. A total of 17 patients with MDD and 17 controls were subjected to an exercise challenge. Plasma suPAR (P-suPAR) was analyzed before, during, and after exercise. There was a significantly higher baseline P-suPAR in the patients with MDD, and the dynamic changes of P-suPAR during the exercise were significantly lower in the patients with MDD, compared with the controls. This study supports the hypothesis that an activation of systemic inflammatory processes, measured as elevated P-suPAR, is involved in the pathophysiology of depression. The study concludes that P-suPAR is influenced by acute exercise, most likely due to release from activated neutrophils.