This study evaluates whether adding home-based resistance training to a multidisciplinary specialist weight management service can promote weight loss and improve physical function, strength, power and quality of life in adults with severe obesity. The study also investigated whether performing resistance exercises as fast as possible can yield further improvements in physical function compared with traditional slow-speed resistance training. All recruited participants completed a 3-month home-based resistance training programme with behavioural support; half of the participants performed resistance exercises in a slow and controlled manner, whereas the other half performed resistance exercises with maximal intentional velocity.
Severe obesity reduces muscle contractile function, which manifests as a diminished ability to perform activities of daily living. These functional impairments often lead to pain during movement and a decreased motivation to exercise. In the United Kingdom (UK), specialist Tier 3 weight management services are provisioned for adults with severe obesity. Tier 3 services comprise a multidisciplinary team (MDT) of specialists and mainly adopt an educational approach, focusing on psychological therapy, dietary modification, pharmacotherapy and physical activity advice. However, current Tier 3 programmes do not specifically address the functional impairments imposed by obesity, which predisposes adults with severe obesity to musculoskeletal pain and pathology. Adding supervised resistance training to MDT weight management programmes has been shown to improve functional capacity in adults with severe obesity. However, supervised interventions place considerable time and resource burdens on the service provider and patient, which may not be conducive to sustained participation. Obese individuals often report feeling too embarrassed to exercise in front of others and feel uncomfortable appearing in public wearing exercise clothing. Home-based exercise is a convenient alternative to supervised interventions and may promote similar functional adaptations. Traditional resistance training typically involves sustained contractions at low to moderate velocities. While this method of training is effective for augmenting maximal strength production, which is executed at slow velocities, it may neglect the development of muscle power. This is problematic because lower-limb power has recently emerged as a critical determinant of function in adults with severe obesity. Power training integrates a high-speed component into conventional resistance training exercises. Research in older adults has consistently shown that power training is superior to conventional slow-speed strength training for improving functionality. Preliminary evidence also exists supporting the superiority of power training in sarcopenic obese adults. Nevertheless, it is unknown whether home-based power training is feasible or effective when added to an MDT weight management programme. The investigators recruited participants from a UK Tier 3 specialist weight management service. In a prospective, parallel groups, randomised design, participants were randomly allocated to a slow-speed strength training group or a high-speed power training group. Both groups completed a 12-week, individualised, home-based resistance training intervention (2x/week) with behavioural support. The high-speed power training group performed resistance exercises with maximal intended concentric velocity whereas the slow-speed strength training group maintained a slow (2-s) lifting speed. Outcomes were assessed at baseline, 3-month (post-intervention), and 6-month (follow-up) endpoints.
Study Type
INTERVENTIONAL
Allocation
RANDOMIZED
Purpose
TREATMENT
Masking
SINGLE
Enrollment
38
Patients completed two home-based resistance training sessions each week on non-consecutive days for 12 weeks. The programme was delivered online via individual playlists on Youtube (YouTube, San Bruno, California, USA), with each playlist involving an individually-prescribed series of pre-recorded exercise videos. Each session involved a dynamic warm-up followed by 11 resistance exercises using body weight and resistance bands, and finished with static stretching. Participants completed 1-2 sets of 5-12 repetitions at 4-7 on a modified 10-point rating of perceived exertion scale, which corresponded to qualitative descriptors of "moderate" to "hard". Resistance training stimuli were progressed weekly by increasing the external load, modifying the exercise selection, increasing the number of repetitions, and/or increasing the number of sets.
After the initial baseline assessment, participants recorded the number of steps they walked daily for seven days using a waist-worn pedometer. Participants maintained their usual physical activity levels during this period. Participants were then encouraged to increase their total steps walked each day by 5% each week during the 12-week intervention.
Lower-limb power (W)
Mean power was measured in the sit-to-stand transfer with a wearable inertial sensor (PUSH, PUSH Inc., Toronto, Canada). The device is worn on the participant's forearm and measures acceleration in the upwards phase of the movement. Power is then calculated as velocity x force, where velocity is the integral of acceleration, and force is the product of mass and acceleration. The test was administered in a firm bariatric chair (height, 48 cm; depth, 56 cm; width, 69 cm). From a seated position, participants were instructed to maintain their arms crossed against their chest and stand up as quickly as possible (legs straight), before returning back to the initial seated position in a controlled manner (full weight on chair). Two warm-up trials were performed, followed by three repetitions separated by 60 seconds of rest. Additional trials were performed if the arms moved away from the chest.
Time frame: 3-month endpoint
Number of recruited participants
Measured as the number of eligible participants who were eligible and consented to participate in the trial. This will be reported in a Consolidated Standards of Reporting Trials (CONSORT) participant flowchart.
Time frame: During the 13-month recruitment period
Number of adverse events
The number of adverse events were recorded to determine the feasibility of the exercise intervention. An adverse event was defined as the occurrence of any untoward medical occurrence in a participant, which does not necessarily have a causal relationship with the exercise intervention. The type of adverse events was also noted.
Time frame: During the 3-month intervention period
Attrition rate
Established as the number of patients who discontinued the exercise intervention.
Time frame: During the 3-month intervention period
Number of patients lost to follow-up
Participants lost to follow-up were characterised as those who completed the exercise intervention but did not complete endpoint testing.
Time frame: 3-month and 6-month endpoints
Number of exercise sessions completed
The number of exercise sessions completed by each participant was recorded. The maximum number of exercise sessions that participants could complete was 24, so adherence ranged from 0 to 24 sessions, with higher scores indicating greater adherence.
Time frame: During the 3-month intervention period
Body mass (kg)
A calibrated digital scale (seca 813, SECA, Birmingham, UK) was used to measure body mass to the nearest 0.1 kg. Participants wore light clothing and removed their footwear before stepping on the scale.
Time frame: 3-month and 6-month endpoints
Waist and hip circumference (cm)
Using a non-stretching measuring tape (seca 201, SECA, Birmingham, UK), waist and hip circumferences were measured to the nearest 0.1 cm. Participants stood upright with their hands by their side and feet positioned shoulder-width apart. The waist circumference measurement was made at the approximate midpoint between the lower margin of the last palpable rib and the top of the iliac crest at the end of a normal expiration. Hip circumference was taken around the widest portion of the buttocks.
Time frame: 3-month and 6-month endpoints
Waist to hip ratio
Waist circumference (cm) was divided by hip circumference (cm) to calculate the waist to hip ratio.
Time frame: 3-month and 6-month endpoints
Six-minute walk test (m)
Participants were instructed to walk at their own maximal pace back and forth along a flat 30 m surface, covering as much ground as they could in six minutes. All instructions, encouragement and monitoring adhered to the guidelines provided by the American Thoracic Society (ATS, 2002).
Time frame: 3-month and 6-month endpoints
Timed up-and-go (s)
Participants sat in a firm bariatric chair and were instructed to stand up, walk three metres before turning 180° around a cone and returning to the chair to sit down.
Time frame: 3-month and 6-month endpoints
30-s chair sit-to-stand test (s)
The test was administered in a firm bariatric chair, which was supported against a wall. Participants began seated and were subsequently instructed to rise to a full standing position (legs straight) and then return to the seat (full weight on chair) with both arms crossed against the chest. A practice trial of two repetitions was given to check correct form, followed by one test trial.
Time frame: 3-month and 6-month endpoints
Shoulder press and seated row one repetition maximums (kg)
Shoulder press and seated row one repetition maximum (1RMs) were determined with resistance machines (Life Fitness, Ely, Cambridgeshire, UK). Participants performed five repetitions at 3 rating of perceived exertion (RPE) ("easy"), three repetitions at 5 RPE ("somewhat hard"), and two repetitions at 8 RPE ("very hard"). Thereafter, the load was progressively increased (2.5-5kg) until the participant could not complete a repetition using correct technique through a full range of motion. The last successful attempt was taken as the 1RM.
Time frame: 3-month and 6-month endpoints
Lower-limb power (W)
Mean power was measured in the sit-to-stand transfer with a wearable inertial sensor. The device is worn on the participant's forearm and measures acceleration in the upwards phase of the movement. Power is then calculated as velocity x force, where velocity is the integral of acceleration, and force is the product of mass and acceleration. The test was administered in a firm bariatric chair. From a seated position, participants were instructed to maintain their arms crossed against their chest and stand up as quickly as possible (legs straight), before returning back to the initial seated position in a controlled manner (full weight on chair). Two warm-up trials were performed, followed by three repetitions separated by 60 seconds of rest. Additional trials were performed if the arms moved away from the chest.
Time frame: 6-month endpoint
Lower-limb movement velocity (m/s)
Mean velocity was calculated in the sit-to-stand movement using a wearable inertial sensor.
Time frame: 3-month and 6-month endpoints
Shoulder press velocity (m/s)
Participants lifted 50% of the load achieved in the 1RM test as fast as possible. Two warm-up trials were performed, followed by three repetitions separated by 60 seconds of rest. A wearable inertial sensor was used to measure mean velocity in the concentric phase of each repetition.
Time frame: 3-month and 6-month endpoints
Shoulder press power (W)
Participants lifted 50% of the load achieved in the 1RM test as fast as possible. Two warm-up trials were performed, followed by three repetitions separated by 60 seconds of rest. A wearable inertial sensor was used to measure mean power in the concentric phase of each repetition.
Time frame: 3-month and 6-month endpoints
EuroQol 5-level questionnaire (EQ-5D-5L)
The EQ-5D-5L is a generic, self-administered measure of health-related quality of life that gathers descriptive information on five main dimensions: mobility, self-care, usual activities, pain/discomfort, and anxiety/depression. Each dimension has five levels: no problems, slight problems, moderate problems, severe problems, and extreme problems. The participant indicates the level that best describes their state of health on that day. This results in a 1-digit number expressing the level selected for that dimension, which were combined to produce a five-digit number describing the participant's health status (ranging from 11111 to 55555). This is then converted to a single index value based on the EQ-5D-5L Crosswalk value set for England that ranges from -0.594 (worst possible health) to 1.000 (best possible health).
Time frame: 3-month and 6-month endpoints
EuroQoL visual analogue scale (EQ-VAS)
The EQ-VAS is a single-item measure of overall health that has demonstrated acceptable psychometric properties in several populations. The participant rates their current perceived health status on a 20 cm, vertical visual analogue scale that ranges from 0 ("The worst health you can imagine") to 100 ("The best health you can imagine"). Higher scores indicate a better health status.
Time frame: 3-month and 6-month endpoints
Obesity and Weight Loss Quality of Life Instrument (OWLQOL)
The OWLQOL measured obesity-specific quality of life, which is self-administered and contains 17-items that explore unobservable needs such as freedom from stigma and attainment of culturally appropriate goals. Each item has a 7-point Likert-like response scale ranging from 0 ("Not at all") to 6 ("A very great deal"). The raw score is transformed to a standardised scale of 0 to 100, where higher scores indicate better quality of life.
Time frame: 3-month and 6-month endpoints
Weight-related symptom measure (WRSM)
The WRSM is a 20-item, self-report measure for the presence and bothersomeness of obesity symptoms. Participants responded either "yes" or "no" as to whether they experienced the symptom in the last four weeks and then rated the degree of bothersomeness that having the symptom caused them. The bothersomeness options are on a 7-point Likert-like response scale ranging from 0 ("Not at all") to 6 ("A very great deal"). A total score is calculated by adding up all the bothersomeness scores for each symptom. Scores range from 0 to 120, with higher scores indicating a higher or worse experience of symptoms.
Time frame: 3-month and 6-month endpoints
Sessional heart rate (%)
Participants recorded their average heart rate, maximum heart rate using their heart rate monitor (FT1, Polar Electro, Kempele, Finland). Recording commenced before the start of the warm-up and stopped immediately after the last resistance exercise (before the cool-down). Heart rate was expressed as a percentage of heart rate reserve.
Time frame: During the 3-month intervention period
Session duration (minutes)
Participants recorded the duration of each session using their heart rate monitor. Recording commenced before the start of the warm-up and stopped immediately after the last resistance exercise (before the cool-down).
Time frame: During the 3-month intervention period
Total number of repetitions during each resistance training session
The total number of repetitions performed during each resistance training session was calculated as: number of sets x number of exercises x number of repetitions in each exercise.
Time frame: During the 3-month intervention period
Step count
Participants recorded the number of steps they walked daily using a waist-worn pedometer. Steps counts are reported as the average number of daily steps performed during each week
Time frame: During the 3-month intervention period
Isometric mid-thigh pull (kg)
Using an analogue back dynamometer (Takei Scientific Instruments Co. Ltd., TKK 5002 Back-A, Tokyo, Japan), participants maximally extended their knees and trunk for five seconds without bending their back. The height of the handle was individually adjusted so that the bar rested midway up the thigh and there was 145° of knee flexion, which was measured with a handheld goniometer (Economy Jamar Goniometer, JAMAR Technologies, Inc., Hatfield, Pennsylvania, USA). Two trials were performed with a two-minute rest period in between. Each trial was recorded to the nearest 1 kg, with the maximum value used for analysis.
Time frame: 3-month and 6-month endpoints
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