Physical activity has its origins in ancient history. It is thought that the Indus Valley civilization created the foundation of modern Yoga, approximately 3000 B.C., during the early Bronze Age . The beneficial role of physical activity in healthy living and preventing and managing health disorders are well documented in the literature. Physical activity provides various significant health benefits. Mechanical stress and repeated exposure to gravitational forces created by frequent physical exercise increase a variety of characteristics including physical strength, endurance, bone mineral density, and neuromusculoskeletal fitness, all of which contribute to a functional and independent existence. Exercise, defined as planned, systematic, and repetitive physical activity, enhances athletic performance by improving body composition, fitness, and motor abilities . The function of physical activity in preventing a wide range of chronic illnesses and premature mortality has been extensively examined and studied. Adequate evidence links medical conditions such as cardiovascular disease and individual lifestyle behaviours, particularly exercise . Regular exercise lowered the incidence of cardio-metabolic illness, breast and colon cancer and osteoporosis . In addition to improving the quality of life for those with nonpsychiatric diseases such as peripheral artery occlusive disease and fibromyalgia, regular physical activity may help alleviate the discomforts of these particular diseases . Exercise also helps in various substance use disorders such as reducing or quitting smoking. As physical exercise strongly impacts health, worldwide standards prescribe a weekly allowance of “150 minutes” of modest to vigorous physical exercise in clinical and non-clinical populations . When these recommendations are followed, many chronic diseases can be reduced by 20%-30%. Furthermore, thorough evaluations of global studies have discovered that a small amount of physical exercise is sufficient to provide health benefits .
A current understanding of the underlying physiological and psychological processes during exercise or physical activity that are implicated in improving mental health is presented in this review article. Exercise OR physical activity AND mental health, exercise OR physical activity AND depression, exercise OR physical activity AND stress, exercise OR physical activity AND anxiety, exercise OR physical activity AND psychosis, exercise OR physical activity AND addiction were used as search terms in PubMed, Google Scholar, and Medline. An overwhelming majority of references come from works published within the recent decade.
Physical health impact on mental health
There is an increasing amount of evidence documenting beneficial impacts of physical activity on mental health, with studies examining the effects of both brief bouts of exercise and more extended periods of activity. Systematic evaluations have indicated better outcomes of mental diseases with physical activity. Numerous psychological effects such as self-esteem, cognitive function, mood, depression and quality of life have been studied . According to general results, exercise enhances mood and self-esteem while decreasing stress tendencies, a factor that is known to aggravate mental and physical diseases . Studies show that people who exercise regularly have better frame of mind. However, it should be highlighted that a consistent link between mood enhancement and exercise in healthy individuals has not been established.
Additionally, human beings produce more of two neurochemicals when they engage in physical activity. Human’s bodies manufacture opioids and endocannabinoids that are linked to pleasure, anxiolytic effects, sleepiness, and reduced pain sensitivity . It has been shown that exercise can improve attention, focus, memory, cognition, language fluency and decision-making for up to two hours . Researchers state that regular physical activity improves the functioning of the hypothalamus-pituitary-adrenal (HPA) axis, lowering cortisol secretion and restoring the balance of leptin and ghrelin (Figure 1) .
Regular exercise has immunomodulatory effects such as optimizing catecholamine, lowering cortisol levels and lowering systemic inflammation. Physical activity has been shown to increase plasma brain-derived neurotrophic factor (BDNF), which is thought to reduce amyloid-beta toxicity linked to Alzheimer’s disease progression .
Although no causal correlations have been proven, methodologically sound research has discovered a related improvement in mentally and physically ill populations. These findings are based on research and studies conducted all across the globe, particularly in the Western hemisphere. In order to address a widespread health problem in India, it is useful to do a literature review that draws on research conducted in a variety of settings. In addition, the prevalence of these mental illnesses and the benefits of exercise as a complementary therapy might be made clear by a meta-analysis of research undertaken in India .
This review also analysed published literature from India to understand the effects of exercise on mental health and the implications for disease management and treatment in the Indian context. Results from Indian studies were consistent with those found in global meta-analysis. The Indian government has made public data on interventions, such as the effects of different amounts of physical exercise. Exercising and yoga have been shown to be effective adjunct therapies for a variety of mental health conditions . Though yoga may not need a lot of effort to perform, other aspects of the programme such as breathing or relaxation exercises may have an impact on a practitioner’s mental health at the same time. Due to its cultural significance as a common physical practise among Indians and its low to moderate activity level, yoga would be an appropriate activity for this assessment .
Yoga as an adjunctive treatment
Although yoga is a centuries-old Hindu practise, it’s possible therapeutic effects have recently been studied in the West. Mind-body approaches have been the subject of a lot of study and some of the findings suggest they may aid with mental health issues of neurosis spectrum. As defined by the National Institutes of Health’s Centre for Complementary and Alternative Medicine, “mind-body interventions” aim to increase the mind’s potential to alter bodily functions . Due to its beneficial effects on the mind-body connection, yoga is used as a treatment for a wide range of conditions. Possible therapeutic benefits of yoga include activation of antagonistic neuromuscular systems, stimulation of the limbic system and a reduction in sympathetic tone.
Anxiety and depression sufferers might get benefits from practising yoga. Yoga is generally safe for most people and seldom causes unintended negative consequences. Adding yoga to traditional treatment for mental health issues may be of benefit. Many of the yoga research included meditation as an integral part of their methodology. Meditation and other forms of focused mental practise may set off a physiological reaction known as the relaxation response. Functional imaging has been used to implicate certain regions of the brain that show activity during meditation. According to a wealth of anatomical and neurochemical evidence, meditation has been shown to have far-reaching physiological effects including changes in attention and autonomic nervous system modulation . Left anterior brain activity which is associated with happiness was shown to rise considerably during meditation. There’s also some evidence that meditation might worsen psychosis by elevating dopamine levels [18-20]. We do not yet know enough about the possible downsides of meditation for patients with mental illness since this research lack randomised controlled trials.
Physical activity and schizophrenia
Schizophrenia is a debilitating mental disorder that often manifests in one’s early years of productive life (late second decade). Remission of this disorder occurs in just a small fraction of cases. More than 60% will have relapses and they might occur with or without noticeable deficits. Apart from delusions, hallucinations, and formal thought disorders, many patients exhibit cognitive deficits that emerge in the early stages of the disease and do not respond adequately to therapy .
Treatment for schizophrenia is challenging to master. Extrapyramidal side effects are a problem with first-generation antipsychotic drugs. Obesity and dyslipidemia have been related to second-generation drugs, which may cause or exacerbate these conditions. The majority of patients do not achieve complete remission and many do not even experience satisfactory symptom relief. Even though certain antipsychotic medications may alleviate or even exacerbate negative and cognitive symptoms, these responses are far less common. This means that patients may benefit from cognitive rehabilitation. Because of their illness or a negative reaction to their medicine, they may also have depressive symptoms. This would make their condition even more disabling. Many patients also deal with clinical and emotional complications. Tardive extrapyramidal illnesses, metabolic syndromes, defect states and attempted suicide are all in this category. Patient compliance with treatment plans is often poor. The caregivers take on a lot of stress and often get exhausted as a result.
Evidence suggests that increased physical activity can aid attenuate some psychotic symptoms and treat medical comorbidities that accompany psychotic disorders particularly those subject to metabolic adverse effects of antipsychotics. Physically inactive people with mental disorders have increased morbidity and healthcare costs. Exercise solutions are commonly recommended to counteract these difficulties and maintain mental and physical wellness .
The failure of current medications to effectively treat schizophrenia and lack of improvement in cognitive or negative symptoms with just medication is an argument in favour of utilising yoga as a complementary therapy for schizophrenia. Even without concomitant medication therapy, co-occurring psychosis and obesity/metabolic syndrome are possible. The endocrine and reproductive systems of drug abusers undergo subtle alterations. Numerous studies have shown that yoga may improve endocrine function, leading to improvements in weight management, cognitive performance, and menstrual regularity, among other benefits. In this context, the role of yoga in the treatment of schizophrenia has been conceptualized. However, yoga has only been studied for its potential efficacy as a therapy in a tiny number of studies. There might be several reasons for this. To begin with, many yoga academies frown against the practice being adapted into a medical modality. The second misconception is that persons with schizophrenia cannot benefit from the mental and physical aspects of yoga practiced in the ways that are recommended. Third, scientists may be hesitant to recommend yoga to these patients because of their lack of knowledge and treatment compliance.
In a randomised controlled experiment with a yoga group (n = 21) and an exercise group (n = 20), the yoga group exhibited a statistically significant reduction in negative symptoms . In accordance with the most recent recommendations of the National Institute for Health and Care Excellence (NICE), the above research provides substantial evidence for the use of yoga in the treatment of schizophrenia. According to a meta-analysis of 17 distinct studies  on the subject, frequent physical activity reduces the negative symptoms associated with schizophrenia considerably.
Physical activity and alcohol dependence syndrome
Substance abuse, namely alcohol, may have devastating effects on a person’s mental and physical health. Tolerance and an inability to control drinking are some hallmarks of alcoholism. Research shows that physical activity is an effective supplement in the fight against alcohol use disorder. In addition to perhaps acting centrally on the neurotransmitter systems, physical exercise may mitigate the deleterious health consequences of drinking. Evidence suggests that persons with alcohol use disorder are not physically active and have low cardiorespiratory fitness. A wide number of medical comorbidities like diabetes mellitus, hypertension and other cardiovascular illness occur with alcohol use disorders. Physical exercise may be highly useful in aiding the management of these comorbidities .
Physical exercise and yoga may help in management of craving for substance when other forms of therapy, such as counselling or medication for craving management are not feasible or acceptable. Physical exercise has been shown to have beneficial effects on mental health, relieve stress, and provide an enjoyable replacement of the substance. However, the patient must take an active role in physical activity-based therapies, rather than passively accept the process as it is, which is in stark contrast to the approach used by conventional medicine. Since most substance use patients lack motivation and commitment to change, it is recommended that physical activity-based therapies be supplemented with therapies focusing on motivation to change to maximise therapeutic outcomes.
One hundred seventeen persons with alcohol use disorder participated in a single-arm, exploratory trial that involved a 12-minute fitness test using a cycle ergometer as an intervention. Statistically significantly fewer cravings were experienced by 40% . Exercise programmes were found to significantly reduce alcohol intake and binge drinking in people with alcohol use disorder in a meta-analysis and comprehensive review of the effects of such therapies .
Physical activity and sleep
Despite widespread agreement that they should prioritize their health by making time for exercise and sufficient sleep, many individuals fail to do so. Sleep deprivation has negative impacts on immune system function, mood, glucose metabolism, and cognitive ability. Slumber is a glycogenetic process that replenishes glucose storage in neurons, in contrast to the waking state, which is organized for the recurrent breakdown of glycogen. Considering these findings, it seems that sleep has endocrine effects on the brain that are unrelated to the hormonal control of metabolism and waste clearance at the cellular level. Several factors have been proposed as potential triggers for this chain reaction: changes in core body temperature, cytokine concentrations, energy expenditure/metabolic rate, central nervous system fatigue, mood, and anxiety symptoms, heart rate and heart rate variability, growth hormone and brain-derived neurotrophic factor secretion, fitness level, and body composition .
After 12 weeks of fitness training, one study indicated that both the quantity and quality of sleep in adolescents improved. Studies using polysomnography indicated that regular exercise lowered NREM stage N1 (very light sleep) and raised REM sleep (and REM sleep continuity and performance) . As people age, both short- and long-term activities have increasingly deleterious effects on sleep. In general, both short- and long-term exercise were found to have a favourable effect on sleep quality; however, the degree of this benefit varied substantially among different sleep components. On measures of sleep quality, including total sleep time, slow-wave sleep, sleep onset latency, and REM sleep reduction, acute exercise had no effect. But both moderate and strenuous exercise has shown to increase sleep quality . According to a meta-analysis of randomized controlled trials, exercise has shown a statistically significant effect on sleep quality in adults with mental illness . These findings emphasize the importance that exercise plays in improving outcomes for people suffering from mental illnesses.
Physical activity in depressive and anxiety disorders
“Depression is the leading cause of disability worldwide and is a major contributor to the global burden of disease” (World Health Organization, 2020). However, only 10%-25% of depressed people actually seek therapy, maybe due to lack of money, lack of trained doctors, or stigma associated with depression . For those with less severe forms of mental illness, such as depression and anxiety, regular physical exercise may be a crucial part of their treatment and management. Exercise and physical activity might improve depressive symptoms in a way that is comparable to, if not more effective than, traditional antidepressants. However, research connecting exercise to a decreased risk of depression has not been analysed in depth . Endorphins, like opiates, are opioid polypeptide compounds produced by the hypothalamus- pituitary system in vertebrates, in response to extreme physical exertion, emotional arousal, or physical pain. The opioid system may mediate analgesia, social bonding, and depression due to the link between b-endorphins and depressive symptoms (Figure 2).
The “endorphin hypothesis” states that physical activity causes the brain to produce more endogenous opioid peptides, which reduces pain and boosts mood. The latter reduces feelings of worry and hopelessness. A recent study that demonstrated endorphins favourably, improved mood during exercise and provided support for these theories, suggesting that further research into the endorphin theory is required .
Physical activity and exercise have been shown to improve depressive symptoms and overall mood in people of all ages. Exercise has been implicated in lowering depressive and anxious symptoms in children and adolescents as well . Pooled research worldwide has revealed that physical exercise more effective than a control group, is a viable remedy for depression . Most forms of yoga that start with a focus on breathing exercises, self-awareness and relaxation techniques have a positive effect on depression and well-being . Despite claims that exercise boosts mood, the optimal kind or amount of exercise required to have this effect remains unclear and seems to depend on a number of factors .
Exercise as a therapy for unipolar depression was studied in a meta-analysis of 23 randomised controlled trials of 977 subjects. The effect of exercise on depression was small and not statistically significant at follow-up, although it was moderate in the initial setting. When compared to no intervention, the effect size of exercise was large and significant and when compared to normal care, it was moderate but still noteworthy . A systematic evaluation of randomised controlled trials evaluating exercise therapies for anxiety disorders indicated that exercise appeared useful as an adjuvant treatment for anxiety disorders, but was less effective than antidepressant treatment