Exercise as it relates to Disease/The effect of resistance training on muscular strength in patients with Anorexia Nervosa

This Wikibooks page is a detailed critique of the research article: “Muscular Strength Changes in Hospitalized Anorexic Patients After an Eight Week Resistance Training Program" [internet]. International Journal of Sports Medicine, Vol 27 660-665, 2006.

What is the background to this research?
Anorexia Nervosa (AN) is characterised by a consistent reduction and restriction of caloric energy intake, disturbances in body weight, fear of weight gain and distorted body image. Recovering from the disorder is difficult and multifaceted. The importance of physical activity has been highlighted in previous literature among eating disorder patients. Beumont and colleagues suggested supplementing an exercise program as early as 1994, alongside existing treatment as a beneficial intervention for patients with eating disorders.

Where is this research from?
This study was performed in partnership with the University of Witwatersrand Medical School, Johannesburg, South Africa, in which the head author was a leading professor within the University’s School of Physiology and co-author was Head of Department in Psychiatry, with previous research history in mental health and illness. Wits Technikon Biokinetics Centre within the University was used for equipment and procedure. No personal bias or conflict of interest appeared to be present.

What kind of research was this?
As a randomised controlled trial, participants were randomly selected to reduce selection bias, and form a basis for statistical tests. This kind of research is prospective and highly regarding when considering the effectiveness of a new or introduced intervention. Randomisation allows for cause-effect relationships between interventions and patient outcomes by balancing characteristics of participants between groups (attribution). .

What did this research involve?
The focus of the study was to investigate the effects of an eight-week resistance training on muscular strength of the elbow and knee flexors and extensors in patients with Anorexia Nervosa. Subjects were categorised into three groups of females aged 15-36. The first group performing the exercise program consisted of seven in-patient Anorexic Exercisers (AE). The second acting-control group consisted of seven Anorexia Controls (AC) not be participating in exercise. The third group consisted of seven Non-anorexic Exercisers (NAE) volunteers acting as controls, who participated in the program to the same extent as the AE.

Table 1. Inclusion Criteria for Subject Groups
The program included a warm-up and cool-down and an alternation of two full-body low-weight resistance program designs for variation. Statistical analysis was measured using a one-way ANOVA test and a Tukey-Kramer post-hoc test for peak torque differences prior to the study, and a t-test post-study (p ≤ 0.05). All isokinetic strength tests were measured using the "Cybex Norm Tm" before and after the program.

What were the basic results?
There was a significant increase in groups AE and AC body mass, BMI, percentage body fat, fat mass and lean body mass after the resistance program. The Beck Depression Inventory score suggested improved positive mental well-being following completion of the program in the AE subjects only.

The isokinetic strength tests showed significant differences only in the right knee and elbow in peak torque for all groups. All measures were increased for the AE group.

Knee Extensors

 * Peak torque in AE and AC pre-intervention was significantly less than NAE
 * Suggests loss of strength as a result of weight loss


 * Peak torque in AE post-intervention was significantly increased (32%) showing adaptive response to overload principle. Whereas AC experienced very little to no change in values. Peak torque was decreased in NAE suggesting lack of overload principle.

Knee Flexors

 * Peak torque in all groups had little change: Suggests the strength of the hamstring group may be preserved in patients with Anorexia Nervosa regardless of the energy and caloric deficiency.

Elbow Extensors

 * Peak torque in all groups before and after the program were statistically similar: Suggests energy and caloric deficiency had no effect on strength of elbow extensors.


 * Peak torque was not increased significantly enough to elicit a response for any and should be revisited in future.

Elbow Flexors

 * Peak torque was initially lower in AC and AE than NAE: Suggests energy and caloric deficiency in Anorexia Nervosa could affect the strength of the elbow flexors.


 * Peak torque following the eight weeks was significantly increased by 40% in the AE group suggesting retraining ability. Decreased slightly in AC and NAE groups.

Evaluation of research and future implications
Given increases in all areas of muscular strength for AE, it can be suggested that the intervention was not interfered by caloric negative energy balance or conflicting behaviours and weightloss.


 * Important to note: Metabolic myopathy can cause a defect in anaerobic glycolysis . This was found to be reversed by implementing re-feeding and increased caloric intake in patients with AN, resulting increased strength . This was neglected in the study, in which its role played an unknown effect in body composition and strength increases.
 * Regarding compulsive behaviours: Although a Beck Depression Inventory score was taken pre- and post-intervention, psychological consideration to thoughts and attitudes could have additionally monitored using journals, entries or logs after each week of the program. This could account for patients attitudes and thought processes during the intervention.

Additionally, the study neglected physiological functionality such as bone mineral density and strength while minimising calorie expenditure. A study by Bratland-Sanda (2018) and authors considered this and found that a further follow-up (6 months after post-intervention) was needed to produced a large increase in bone mineral density.

Implications of neuromuscular factors from muscular strength, such as synergist coordination, increased antagonist inhibition and excitation of motor neurons were not measured. Conducting an EMG, seen in other studies measure deeper associations between torque and neuromuscular factors contributing to strength increase. However this becomes an expensive process.

Focussing on methodology of the tests, measures were taken by the same person to reduce inter-observer variability. However, only female participants were tested on, with no male conclusions or generalisability for in-patient population.

Practical advice
Thorough critique defines this study as appropriate and successful. It carried out a functioning and in-depth resistance program which produced positive results and statistical significance towards the overall health in patients with Anorexia nervosa. Additional tests and improvements in generalisability could be revisited, as well as measuring different duration programs and follow-up procedures.

Given the increased measures in body composition and peak torque of muscles, practical advice should suggest prescribing a structured low resistance training program to in-patients to increase muscular strength. Implementing this into hospital environments, alongside weight-restorative 're-feeding' can ultimately improve their health and well-being.

Further information/resources
If you know someone who may be suffering from an eating disorder visit Lifeline or Butterfly Foundation.

The original journal article can be found here.

The following resources can provide additional information discussed:


 * https://www.nationaleatingdisorders.org/learn/by-eating-disorder/anorexia
 * https://www.ccjm.org/content/87/6/361
 * https://www.healthyplace.com/blogs/survivinged/2020/11/strength-training-in-eating-disorder-recovery