Force-generating capacity, skeletal health and functional performance in patients with mental and behavioural disorders: The impact of strength training
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Patients with schizophrenia spectrum disorders and substance use disorders (SUDs) have poor physical health and a shortened life expectancy compared to the general population. The new standardized guidelines regarding the treatment of patients with mental illne and SUDs recognize the patient groups’ poor physical health and state that exercise should be an integrated element of standard treatment. Despite increased interest in attending to the patient’s physical health, little is yet known regarding the skeletal muscle force-generating capacity (FGC) in the functionally relevant lower extremities and its implications for functional performance in patients with schizophrenia spectrum disorders. Previous research shows impaired skeletal muscle FGC and skeletal health in patients with SUDs. Further, including short term maximal strength training (MST) interventions as part of clinical treatment to help counteract these physical health issues remain insufficiently explored in both patient groups. In addition, the Patient Activation Measure-13 (PAM-13) is a questionnaire that can assist therapists in identifying areas where more help or knowledge would be advantageous to the patients for a better involvement in their own health management, however the test-retest reliability and internal consistency of this questionnaire remains to be investigated. The aims of this thesis were: 1) To assess and compare the leg press skeletal muscle FGC, measured as one repetition maximum (1RM) and rapid force development, and functional performance in weight bearing activities in patients with schizophrenia spectrum disorders to that of healthy references. 2) To investigate the test-retest reliability and internal consistency of PAM-13 in patients with schizophrenia spectrum disorders and SUDs. 3) To investigate the 12-week effects of leg press MST on skeletal muscle FGC, functional performance, health-related quality of life and patient activation in patients with schizophrenia spectrum disorders and compare the results to healthy reference values. 4) To investigate the 12-week effects of hack squat MST on skeletal muscle FGC (1RM and rate of force development, RFD), skeletal health and mental health in amphetamine users taking part in three months of residential treatment. In paper I, we assessed and compared leg press skeletal muscle FGC, and functional performance in weight bearing activities in 48 outpatients with schizophrenia spectrum disorders to that of 48 age- and gender-matched healthy references. We found that allometrically scaled 1RM was reduced in men (19%) and tended to be reduced in women (13%) with schizophrenia, while allometrically scaled rapid force development were reduced in both genders (men: 30%, women: 25%). Additionally, compared to healthy references the patients scored significantly lower on all tests of functional performance measured as stair climbing (63%), 30-second sit-to-stand test (30sSTS, 48%), six-minute walk test (6MWT, 22%), walking efficiency (14%) and unipedal stance test with eyes open (20%) and closed (73%). The reduced functional performance was associated with both measures of skeletal muscle FGC. In paper II, we investigated the test-retest reliability and internal consistency of the PAM-13 in patients with SUDs and schizophrenia spectrum disorders. We found both the test-retest reliability and internal consistency of PAM-13 to be good, with intraclass correlation coefficient and Cronbach’s a, respectively, both being ≥0.70. In paper III, the patients from paper I were randomized to take part in either a training group (TG) performing MST in a leg press apparatus two days a week for 12 weeks or a control group (CG) receiving two introductory training sessions and encouragement to train on their own. Following the training intervention, the patients’ skeletal muscle FGC and functional performance were compared to the results of a healthy reference group. The TG improved 1RM and rapid force development by 28% and 20%, respectively, reaching levels similar to that of the healthy reference group. No changes were observed in the CG. MST improved 30sSTS performance by two full stands in the TG. The CG also improved 30sSTS performance by one full stand and the changes were not apparent as between group differences. This improvement in 30sSTS performance was, however, associated with rapid force development improvements. No improvements were seen in health-related quality of life or patient activation. In paper IV, amphetamine users taking part in a residential treatment program were randomized to either a TG performing hack squat MST three days per week for 12 weeks or a CG who were not allowed to perform strength training. The TG improved 1RM and RFD by 70% and 86%, respectively, while no changes were observed in the CG. More importantly, the TG improved bone mineral density (BMD) at the lumbar spine (3.6%), trochanter (3.5%) and intertrochanteric hip (2.7%). Improvements in 1RM were associated with improvements in BMD at the lumbar spine and total hip, while RFD improvements were associated with BMD improvements at the lumbar spine. No between group differences were observed in depression or anxiety score. In conclusion, the papers in this thesis show that skeletal muscle FGC and functional performance is reduced in patients with schizophrenia spectrum disorders and that short term MST interventions can restore skeletal muscle FGC in patients with schizophrenia spectrum disorders and improve BMD at key sites prone to bone loss in amphetamine users. MST seems to have some effects on functional performance and mental health, but limited effect on health related quality of life and patient activation. Lastly, the lack of improvements in patient activation and in the physiological measures in the control groups imply that structured training and adherence support is necessary. Despite increased interest in attending to the patient’s physical health, little is yet known regarding the skeletal muscle force-generating capacity (FGC) in the functionally relevant lower extremities and its implications for functional performance in patients with schizophrenia spectrum disorders.