Effects and Acceptability of an Individualized Home-Based 10-Week Training Program in Adults with Myotonic Dystrophy Type 1

Abstract

Background:

Muscle weakness is a cardinal sign of myotonic dystrophy type 1, causing important functional mobility limitations and increasing the risk of falling. As a non-pharmacological, accessible and safe treatment for this population, strength training is an intervention of choice.

Objective:

To document the effects and acceptability of an individualized semi-supervised home-based exercise program on functional mobility, balance and lower limb strength, and to determine if an assistive training device has a significant impact on outcomes.

Methods:

This study used a pre-post test design and men with the adult form of DM1 were randomly assigned to the control or device group. The training program was performed three times a week for 10 weeks and included three exercises (sit-to-stand, squat, and alternated lunges). Outcome measures included maximal isometric muscle strength, 10-Meter Walk Test, Mini-BESTest, 30-Second Chair Stand Test and 6-minute walk test.

Results:

No outcome measures showed a significant difference, except for the strength of the knee flexors muscle group between the two assessments. All participants improved beyond the standard error of measurement in at least two outcome measures. The program and the device were well accepted and all participants reported many perceived improvements at the end of the program.

Conclusions:

Our results provide encouraging data on the effects and acceptability of a home-based training program for men with the adult form of DM1. These programs would reduce the financial burden on the health system while improving the clinical services offered to this population.

Keywords

Myotonic dystrophy exercise muscle strength walking postural balance patient acceptance of health care

INTRODUCTION

Myotonic dystrophy type 1 (DM1) is the most pre-valent adult-onset neuromuscular disorder in Canada and worldwide [1, 2]. It is a slowly progressive, autosomal dominant disorder caused by an unstable expansion of the nucleotide triplet cytosine, thymine and guanine (CTG) located on chromosome 19. It is subdivided into five clinical phenotypes, defined by the age at the onset of symptoms and the number of CTG repeats: congenital, infantile/childhood, juvenile, adult/classic, and late-onset [3]. In the adult (classic) phenotype, clinical signs generally appear between the ages of 20 and 40, and signs and symptoms are fewer and milder in the late-onset phenotype [4]. DM1 affects various systems, including the nervous, cardiac, digestive, endocrine and respiratory systems as well as the skeletal muscle system [1, 5].

Muscle weakness is a cardinal sign of the disease, with people losing between 24.5–52.8% of their maximum muscle strength over a 9-year period depending on muscle groups [6]. Muscle weakness, which progresses from distal to proximal, causes important limitations in activities, mainly related to functional mobility (transfer from sit to stand, walking) [7] as well as an increased risk of falling [8]. People with DM1 experience significant restrictions related to work, leisure and activities of daily life (personal care and home maintenance) [9, 10]. According to recent studies, there are sex-related differences in clinical manifestations. Men have more severe muscular impairments (weakness and myotonia) [11] and show a significantly greater rate of decline in their muscle strength as compared to women [6].

No curative treatment is currently available for DM1 [12], so it is essential to develop interventions aimed at reducing the severity and impact of impairments, including muscle weakness. Strength training is a great option since it is a low-cost and non-pharmacological accessible treatment. Although strength training has been shown to be safe in this population [13], only few studies have addressed its efficiency to increase maximal muscle strength, but they all showed positive results [14, 15]. Training programs that are part of a supervised rehabilitation or that take place in structured sport/fitness centers have clear benefits, such as the increased supervision and training intensity. However, the lack of access to transportation [10], costs and availability of these programs are major barriers for adults with DM1. One solution could be the development of a home-based training program, which could increase the acceptability of the intervention. One previous home-based training study highlighted that strategies involving a research or rehabilitation team (e.g., phone calls, training supervision) seem necessary to ensure participants’ adherence in DM1 population [16]. Recent technological advances lead to the development of assisted training devices that can encourage patients to perform their exercises and also capture the actual performance of patients while doing their exercises [17].

The main objective of the study is to document the effects of a 10-week individualized progressive and semi-supervised home-based exercise program on functional mobility, balance and lower-limb muscle strength in DM1 adult population. The secondary objectives are: 1) to evaluate the retrospective acceptability of the training program and 2) to determine if the addition of an assistive training device [17] has a significant impact on the improvements in comparison to a semi-supervision by a physiotherapist.

MATERIALS AND METHODS

This study used a pre-post test design.

Participants

People with DM1 were recruited using a convenience sampling strategy from a registry of 404 (190 men and 214 women) patients followed at the Neuromuscular Clinic of the Centre Intégré Universitaire de Santé et de Services Sociaux du Saguenay–Lac-St-Jean (CIUSSS-SLSJ) (Saguenay, Canada). This study was limited to men with the adult phenotype, in order to have the most homogenous sample in terms of potential confounding factors related to strength training. Participants needed to have a genetically confirmed DM1 diagnosis, be at least 18 years old, live in the Saguenay—Lac-Saint-Jean region, be authorized by a neurologist to take part in a training program, have access to Internet at home and be able to provide their written informed consent. The exclusion criterion was to have other diseases causing physical limitations. Participants were randomly assigned to the control or device group. The Ethics Review Board of the CIUSSS-SLSJ (Saguenay, Canada) approved the study.

Intervention

For the two groups, the individualized semi-super-vised home-based training program was performed three times a week for a period of 10 weeks [18]. It included three exercises (sit-to-stand, squat [wall support] and alternated lunges) with a one-minute rest between the sets and a two-minute rest between each exercise. For all exercises, each repetition had to be executed in six seconds (three seconds for each movement phase: concentric and eccentric). For example, for the squats, participants were instructed to move slowly from a standing posture to a half-sitting posture over a 3-second movement time, and then to slowly return to their standing position. During each session, two to four sets were prescribed with five to eight repetitions for each exercise, at a target effort rate (intensity) of 13–15 (“a little difficult” to “difficult”) on Borg’s perceived exertion scale of 6 to 20 points [19, 20]. Participants were instructed not to hold their breath during the exercises to minimize exercise-induced blood-pressure elevation. The exercises were carried out using the weight of the body itself. Before starting the training program, a home visit was carried out by the physiotherapist (I.L.) in order to ensure safety and proper execution of the exercises and to adapt (e.g. by allowing arm support) the program according to individual capacities, in terms of execution and number of sets and repetitions for each exercise. The physiotherapist determined the baseline number of sets and repetitions for each exercise depending on the participant’s level of comfort and level of difficulty felt during the execution of each exercise. The physiotherapist supervised the training by doing follow-up phone call once a week to ensure safety and an adapted progression of the number of sets and repetitions for each exercise, taking into account the level of difficulty felt [19] during the execution of these exercises in the previous week.

For the device group, an assistive training device made up of three components, namely a nano-computer Raspberry Pi 3 1 , a custom smart bracelet with an inertial measurement unit developed earlier by our team [17] and a small common speaker, was given to each participant. Participants were asked to wear the bracelet every day and charge it at night. The usefulness of the bracelet lies in the fact that it is able to automatically recognize, via an artificial intelligence algorithm [21] personalized to each participant, the three exercises prescribed in this study (sit-stand, squat and alternated lunges). As the execution of the training program required several sets including several repetitions for each exercise, the activation of a training mode was possible by pressing a button on the bracelet and holding it down for a few seconds. If the training mode was activated, a step-by-step guidance protocol was launched to accompany the participant by pre-recorded vocal instructions, through the speaker, throughout his session. In addition, since the assistive training device could be updated remotely if necessary, the guided training could be modified easily, always included the right number of exercises (series, repetitions), and allowed the perfect sequencing of the different repetitions (for example performing two sets of eight squats with 5 seconds between each repetition and a minute of rest between each set). Finally, the assistive training device could remind participants to execute their training program if it wasn’t completed at the scheduled time.

Data collection

Participants were assessed over two sessions during the same week by two trained physiotherapists (I.L. and M-P R.) before the training program (T0) and after the 10-week program (T1) (September 2019 to December 2019) at the Neuromuscular Clinic of the Centre Intégré Universitaire de Santé et de Services Sociaux du Saguenay–Lac-St-Jean (CIUSSS-SLSJ) (Saguenay, Canada). Outcome measures were administered using the standard operating procedures (SOP). During the first session, lower limb isometric strength and the anthropometric measurement were evaluated (M-P. R.). During the second session, all the other outcome measures were administrated (I.L.). A sociodemographic questionnaire was completed at the beginning (T0) to document information about age and mobility stages. The number of CTG and the MIRS came from the medical file. The physiotherapist (I.L.) completed a logbook after each follow-up phone call, which included information about the recommended number of sets and repetitions for each exercise. The participant also completed a logbook after each training session (number of sets and repetitions completed and clinical manifestations after the training [e.g. fatigue, pain]). Pictograms were added to the logbook as this population tends to have a low health literacy. The physiotherapist monitored detrimental effects during the weekly phone call; a detrimental effect was taken into account if the participant needed to seek medical help for the event or if the event kept the participant from participating in the program for any period of time. After the 10-week program, individual semi-structured interviews were carried out and recorded by a research professional specialized in qualitative methods (V.T.) and a physiotherapist (I.L.). The interview guide was developed by two research professionals and a physiotherapist (I.L.) based on the seven constructs (affective attitude, burden, ethicality, intervention coherence, opportunity cost, perceived effectiveness and self-efficacy) of the theoretical framework of acceptability. Sekhon et al. [22] defined this framework as “a multi-faceted construct that reflects the extent to which people receiving a healthcare intervention considers it to be appropriate, based on anticipated or experiential cognitive and emotional responses to the intervention”. Participants were asked about the factors that had positive and negative impacts on program adherence.

OUTCOMES MEASURES

Anthropometric measurements

Participants were measured and weighted using a mechanical column scale. The formula for calculating body mass index (BMI) was weight in kilograms divided by height in meters squared.

Adherence

Adherence was measured using the information reported in the participants’ logbook. The adherence rate was calculated by dividing the number of exercise sessions the participants had reported performing by the number of sessions they were expected to perform throughout the study (30 sessions).

Quantitative maximal muscle strength

The maximal isometric muscle strength (MIMS) of six lower limb muscle groups (hips [flexors, extensors, abductors]; knees [extensors, flexors]; ankles [dorsiflexors]) was evaluated using the quantified muscle testing (QMT) [23] with a linear electronic handheld dynamometer (MEDupTM, Atlas medic, Québec, Canada). The MIMS was recorded in newton. Two trials were completed for each muscle group. When a difference of over 10% was obtained between the two trials, a third one was performed. The maximal isometric torque in newton-meters (Nm) was calculated by multiplying the unit of force in newton by the corresponding lever arm in meter. Out of the three trials, the mean result from the 2 measurements that were the closest for each muscle group was used for analysis. The reliability (intra-rater) of the quantified muscle testing (QMT) for maximal knee extensors strength is excellent in DM1 population (ICC: 0.98) and its concurrent validity was demonstrated with the Biodex (ρ: 0.98) [24].

Balance

Balance was evaluated with the Mini Balance Evaluation Systems Test (Mini-BESTest) [25], a 14 item ordinal scale graded from 0 to 2 (potential total score of 28 [best performance]). Its construct validity was demonstrated in DM1 population [26]. A cut-off score of 21.5 was found to identify fallers [26]. The intra-rater reliability of the Mini-BESTest is good in the elderly population (ICC: 0.84) [27].

Functional mobility

The ability to perform sit-to-stand transfers without using the upper limbs was assessed using the 30-Second Chair Stand Test (30CST) [28]. The number of full sit-to-stands correctly performed in 30 seconds was recorded and the test was performed twice. The reliability (test-retest) of the 30CST is excellent in DM1 population (ICC: 0.96) [29]

Short distance walking speed was assessed with the 10-Meter Walk Test (10mWT) at self-selected and maximal speeds (1 trial for each) [30]. Participants had to walk at their self-selected and maximal (without running) speeds on a 14-meter distance (walking aid permitted). The time in seconds to complete the inner 10 m (meter 2 to 12) of the corridor was recorded and the speed in m/s was thereafter calculated. The test-retest reliability of the 10 mWT at self-selected and maximal speeds is excellent in DM1 population (ICC: 0.99 respectively) [29].

Walking endurance was assessed using the 6-minute walk test (6MWT) [31]. The distance walked along a 30-meter linear corridor over a 6-minute period was recorded (walking aids permitted, 1 trial).

The perceived lower limb functional capacity was assessed using the lower extremity functional scale (LEFS) [32], a 20 item questionnaire graded from 0 (extreme difficulty/unable to perform activity) to 4 (no difficulty) (potential total score of 80 [no functional limitations]). The intra-rater reliability of the French version is excellent (ICC: 0.92) [33].

STATISTICAL ANALYSIS

To be included in the statistical analysis, each participant needed an attendance rate of at least 70% (i.e. 21 of the 30 training sessions). Descriptive statistics were used for continuous variables (mean, median, SD, ranges), and frequency and percentage for categorical variables. Participant’s characteristics between groups were compared using a Wilcoxon rank-sum test. Predicted strength was calculated using Hogrel’s equations [34]. An intention-to-treat analysis approach was applied and a generalized linear mixed-model repeated measurement was used for evaluating time, group and interaction effects (time^*group) of functional mobility and balance performance and the quantified MIMS over time in both groups. Individual difference between T1 and T0 performance (Δ) was calculated for each outcome measures and analyzed using the standard error of measurement (SEM). When the SEM was not available for the DM1 population or similar population, the SEM were calculated using the ICC (test-retest or intra-rater) available in the literature for the DM1 population or the elderly community, with the SD obtained in our sample at T0 as follows: SD_T0^*√(1-ICC). The following SEM values were used for the analysis: 10 mWT self-selected speed (0.025) [29], 10 mWT maximal speed (0.037) [29], 30s-CST (1.99) [29], 6MWT (21.0) [35], Mini-BESTest (3.06) [27], LEFS (4.77) [33] and MIMS of hip flexors (4.5) [23], hip extensors (4.9) [23], hip abductors (2.0) [23], knee flexors (3.9) [23], knee extensors (1.05) [24], ankle dorsiflexors (1.0) [23]. For any analysis, a p value < 0.05 was considered significant. Data were analysed using IBM SPSS Statistics for MAC, Version 20.0 (Armonk, NY: IBM Corp). For the qualitative analysis, the physiotherapist listened to the recordings [36] of the individual interviews and did a content analysis following the acceptability framework [22] with emerging themes (mixed coding method) [37].

RESULTS

A total of 20 men were initially included in this study, which represents the sample size we were aiming for. Fifteen completed the 10-week training program (control group: 10 and device group: 5) and were included in the statistical analysis. The dropout rate was 25% (control group: 1 and device group: 4), and the main reasons for leaving were the following: change in family responsibilities (n = 1), surgery (n = 1) and death in the family (n = 2). The physiotherapist excluded one participant from the control group after week five because it had been impossible to reach him by phone since the beginning of the program. One participant from the device group was transferred to the control group in the second week due to problems with his Internet connection at home. Table 1 shows the characteristics of the 15 participants. A total of two participants (13.3%) used a walking aid inside their home (walking stick [n = 1], 2-Wheel Walker [n = 1]). Three participants were considered at risk of falling at T0 and T1 (score MiniBESTest <21.5 [26]). Participants reported an adherence rate of 83.3 % and more. Individual number of sets and repetitions completed for each exercise at week 1, 5 and 10 are presented in the Table 2. The majority of participants increased the number of sets and repetitions throughout the program, with the exception of two participants who did not want to increase these parameters because they found the program difficult enough. One participant reported persistent lower back pain as a detrimental effect at the end of the training program. A total of 10 participants (control group: 7 [70%] and device group: 3 [60%]) out of the 15 who completed the exercise program did the individual interviews. The mean duration of individual interviews was 33.0 minutes.

Table 1

Characteristics of the study population

	Total (n = 15)	Control group (n = 10)	Device group (n = 5)	p value^*
Age (years)	47.7 (10.9) (28.0 to 62.0)	48.4 (11.1) (28.0–62.0)	46.4 (11.7) (33.0–61.0)	0.679
CTG (number of repeats)	559.7 (374.1) (65.0–1300.0)	494.5 (360.6) (65.0–1200.0)	690.0 (406.8) (250.0–1300.0)	0.371
MIRS (/5)	3.0 (1.0)^* (1.0–5.0)	2.8 (1.0)^** (1.0–4.0)	3.4 (1.1) (2.0–5.0)	0.301
Adherence rate (%)	96.4 (5.1) (83.3–100.0)	96.7 (4.2) (90.0–100.0)	96.0 (7.2) (83.3–100.0)	0.859
BMI (Kg/m²)	27.7 (8.0) (16.3–39.8)	28.7 (8.8) (16.3–39.8)	25.8 (6.6) (21.4–37.5)	0.768

^*n = 14, ^**n = 9. Results are presented as mean (SD) and (range). CTG: triplet cytosine, thymine and guanine; BMI: body mass index.

Table 2

Number of sets and repetitions for each exercise

ID		Week 1						Week 5						Week 10
		Exercise						Exercise						Exercise
	Squat		Sit-to-stand			Lunges		Squat		Sit-to-stand		Lunges		Squat		Sit-to-stand		Lunges
		S	R	S	R	S	R	S	R	S	R	S	R	S	R	S	R	S	R
Control group	1	3	5	3	5	3	5	3	5	3	5	3	5	4	5	4	5	4	5
	2	1	5	1	5	1	5	3	5	3	5	3	5	3	5	3	5	3	5
	3	3	5	3	5	2	5	3	5	3	5	3	5	3	5	4	5	3	6
	4	3	5	3	5	2	5	3	5	3	5	2	5	4	5	4	5	2	5
	5	3	5	3	5	3	5	3	8	3	8	3	8	4	8	4	8	4	8
	6	3	5	3	5	3	5	4	5	4	5	4	5	4	9	4	9	4	9
	7	3	5	3	5	3	5	4	6	4	6	4	6	4	8	4	8	4	8
	8	3	5	3	5	3	5	4	5	4	5	4	5	4	6	4	6	4	6
	9	4	5	4	5	4	5	4	5	4	5	4	5	4	8	4	8	4	8
	10	3	5	3	5	3	5	3	5	3	5	3	5	3	5	3	5	3	5
Device group	11	2	5	2	5	1	5	3	5	3	5	2	5	3	5	3	5	2	5
	12	3	5	3	5	3	5	6	5	6	5	6	5	8	5	8	5	8	5
	13	2	5	2	5	2	5	2	5	2	5	2	5	2	5	2	5	2	5
	14	3	5	3	5	3	5	3	5	4	5	3	5	3	8	4	8	3	5
	15	3	5	3	5	3	5	3	5	3	5	3	5	4	5	4	5	4	5

No increase during the training program. S: serie, R: repetition.

TRAINING PROGRAM EFFECTS

No statistical differences between the measurements for the control and the device groups and the interaction time^*group effects were obtained for the mean of all functional mobility, balance and strength tests, except for the MIMS of the knee flexors muscle group, where a significant improvement was noted between the two assessments (T1-T0) (p = 0.033) (Table 3 and 4). Tables 3 and 4 show the median results for the functional mobility and balance tests as well as the MIMS.

Table 3

Functional mobility activities and balance results (whole cohort)

Times	Mobility					Balance
	10 mWT self-s (m/s)	10 mWT max (m/s)	30 CST (# repetition)	6 MWT (m)	LEFS (/80)	MiniBESTest (/28)
T0	1.24 (0.69–1.57)	1.75 (0.81–2.16)	15.0 (0–29.5)	490.0 (185.1–648.2)	66.0 (33.0–80.0)	24.0 (1 –28.0)
T1	1.21 (0.69–1.61)	1.75 (0.83–2.18)	14.5 (0–32.5)	480.0 (196.1–660.0)	74.0 (33.0–80.0)	25.0 (2.0–27.0)
Δ	0.015 (–0.09 –0.22)	0.012 (–0.13–0.20)	0.0 (–6.0–6.50)	11.8 (–70.9–84.2)	1.0 (–8.0–10.0)	1.0 (–2.0–4.0)
p value	T: 0.285	T: 0.564	T: 0.978	T: 0.551	T: 0.734	T: 0.109
	G: 0.745	G: 0.337	G: 0.544	G: 0.372	G: 0.882	G: 0.143
	TG: 0.668	TG: 0.528	TG: 0.294	TG: 0.184	TG: 0.226	TG: 0.910

Results of T0 and T1 are presented as median (range). Results of Δ (T1-T0) are presented as median (range). 10 mWT: 10-Meter Walk Test; 30CST: 30-Second Chair Stand Test; 6 MWT: 6-minute walk test; LEFS: Lower Extremity Functional Scale; MiniBESTest: Mini Balance Evaluation Systems Test. p value: T: time effect; G: group effect; TG: interaction time^*group effect.

Table 4

Maximal isometric muscle strength of the lower limbs (Nm) (whole cohort)

Times	Hip			Knee		Ankle
	Flexors	Extensors	Abductors	Flexors	Extensors	Dorsiflexors
T0	86.9 (57.3–157.6)	187.2 (72.2–286.4)^*	77.1 (50.6–132.0)	67.0 (48.1–117.0)	117.2 (15.6–211.4)	17.7 (6.7–29.4)
T1	97.3 (55.4–174.8)	195.8 (71.9–389.4)	90.8 (42.5–131.6)	84.0 (53.4–125.9)	109.0 (15.2–191.8)	17.7 (6.7–33.7)
Δ	4.1 (–9.8–25.8)^*	–2.5 (–49.0–25.9)^*	–0.5 (–18.5–27.3)	6.6 (–12.8–26.4)	–0.4 (–47.9–48.9)	1.0 (–2.9–5.2)
p value	T: 0.078	T: 0.391	T: 0.558	T: 0.033	T: 0.851	T: 0.138
	G: 0.781	G: 0.957	G: 0.679	G: 0.381	G: 0.293	G: 0.643
	TG: 0.079	TG: 0.469	TG: 0.503	TG: 0.417	TG: 0.859	TG: 0.566

Results of T0 and T1 are presented as median (range). Results of Δ (T1-T0) are presented as median (range). Number of participants: ^* (n = 14). p value: T: time effect; G: group effect; TG: interaction time^*group effect.

Individual results for all outcome measures are shown in Tables 5 to 8. For the functional mobility and balance outcome measures, all participants showed an improvement beyond the SEM in at least one of the six outcome measures, with the exception of two participants who displayed no improvement. For the lower limb strength, participants had improvements outside the SEM for one to five of the six muscle groups. The hip extensors improved the least during the program, with only two participants having improved outside the SEM. However, for each of the other muscle groups, at least 6 participants showed improvements outside the SEM. Overall, all participants showed improvements beyond the SEM in at least two outcome measures and five of them showed improvements in six outcome measures (see Table 9). Some participants had a decrease in functional mobility and MIMS for the lower limbs outside the SEM (Tables 5 –8).

Table 5

Difference between T0 and T1 for each participant for all functional mobility activities and balance

Participant ID		Mobility										Balance
		10mWT	%	10mWT	%	30CST	%	6MWT	%	LEFS	%	MiniBESTest	%
		self-s (m/s)	IMP	max (m/s)	IMP	(# repetition)	IMP	(m)	IMP	(/80)	IMP	(/28)	IMP
Control group	1	0.027^*	2,2	–0.015	–0,9	1.5	10,0	18.3	4,2	7.0^*	10,1	3,0	13,0
	2	0.015	1,5	0.131^*	8,0	6.0^*	50,0	–18.8	–3,8	2.0	5,41	0,0	0,0
	3	–0.080^**	–7,2	–0.054^**	–4,2	0.0	0,0	21.7^*	7,8	0.0	0,0	4,0^*	36,4
	4	–0.092^**	–7,6	–0.053^**	–3,4	–0.5	–3,7	–70.9^**	–15,9	1.0	1,6	–1,0	–4,2
	5	0.087^*	6,9	0.192^*	10,8	–3.5^**	–12,5	37.5^*	8,5	–4.0	–5,0	1,0	3,9
	6	–0.092^**	–7,2	0.012	0,6	–2.5^**	–10,6	49.4^*	9,6	5.0^*	6,7	2,0	8,3
	7	0.102^*	7,2	–0.125^**	–6,7	1.5	10,0	33.8^*	6,6	2.0	2,6	1,0	4,0
	8	0.180^*	17,5	0.043^*	2,6	–0.5	–3,3	27.5^*	5,4	10.0^*	15,6	0,0	0,0
	9	0.075^*	5,3	0.203^*	10,3	6.5^*	33,3	11.8	1,8	0.0	0,0	–1,0	–3,6
	10	–0.042^**	–3,6	0.027	2,0	1.0	10,0	84.2^*	28,0	–2.0	–5,1	–2,0	–8,3
Mean		0.018	1.5	0.036	1.9	0.95	9.2	19.4	5.2	2.1	3.2	0.7	4.9
Device group	11	0.000	0,0	0.023	2,8	0.0	0,0	11.0	5,9	–8.0^**	–18,2	1,0	100,0
	12	0.000	0,0	0.149^*	8,5	–6.0^**	–30,8	–10.1	–1,8	2.0	2,6	1,0	4,6
	13	0.219^*	30,1	–0.022	–2,2	0.0	0,0	–25.1^**	–8,6	–6.0^**	–13,3	1,0	0,0
	14	–0.050^**	–3,9	–0.117	–6,5	3.0^*	10,2	–14.2	–2,8	0.0	0,0	1,0	3,9
	15	0.038^*	2,4	–0.041^**	–1,9	–2.0^**	–12,9	0.3	0,05	6.0^*	9,1	1,0	3,9
Mean		0.041^*	5.2	–0.0016	0.16	–1.0	–11.2	–7.63	–1.5	–1.2	–4.0	0.8	22.4
Total mean		0.026^*	2.9	0.023	1.3	0.3	4.1	10.4	3.0	1.0	0.8	1.0	10.8

^*Improvement outside the standard error of the measurement (SEM). ^** Worsening outside the SEM. % IMP: percentage of improvement between T1 and T0. 10 mWT: 10-Meter Walk Test; 30 CST: 30-Second Chair Stand Test; 6 MWT: 6-minute walk test; LEFS: Lower Extremity Functional Scale; MiniBESTest: Mini Balance Evaluation Systems Test.

Table 6

Individual results for hip maximal isometric muscle strength

Participant ID		Flexors				Extensors				Abductors
		T0 measured strength	% of predicted strength	Δ	% of improvement	T0 measured strength	% of predicted strength	Δ	% of improvement	T0 measured strength	Δ	% of improvement
		(Nm)				(Nm)				(Nm)
Control group	1	106.4	94.0	14.1^*	13.3	236.9	104.2	–20.1^**	–8.5	111.7	6.7^*	6.0
	2	—	—	—	—	178.8	113.8	–30.3^**	–17.0	69.3	27.3^*	39.4
	3	57.3	72.6	2.5	4.3	72.2	49.1	–0.3	–0.4	55.8	–11.9^**	–21.3
	4	98.2	80.1	4.6^*	4.7	267.5	105.7	–49.0^**	–18.3	86.8	–18.5^**	–21.3
	5	94.2	84.8	3.1	3.3	197.8	88.0	–1.9	–1.0	105.1	–11.8^**	–11.2
	6	88.7	96.7	24.4^*	27.6	257.8	141.5	–38.2^**	–14.8	69.8	4.5^*	6.4
	7	100.5	84.3	11.2^*	11.1	286.4	112.3	25.9^*	9.0	132.0	–0.5	–0.4
	8	75.6	89.1	3.8	5.1	164.0	109.2	–12.8^**	–7.8	50.6	–7.7^**	–15.2
	9	122.5	131.1	4.4	3.6	235.4	140.4	–3.1	–1.3	119.9	–8.0^**	–6.7
	10	85.0	86.1	25.8^*	30.4	159.9	82.0	24.2^*	15.1	83.2	15.1^*	18.2
Mean		92.0	91.0	10.4^*	11.5	205.7	104.6	–10.6^**	–4.5	88.4	–0.5	–0.6
Device group	11	75.9	78.4	–2.7	–3.5	137.9	73.1	–1.8	–1.3	61.1	4.6^*	7.5
	12	69.2	82.4	–0.2	–0.2	132.9	82.7	1.4	1.1	76.5	–3.8^**	–4.9
	13	65.2	69.9	–9.8^**	–15.1	142.6	78.9	–13.6^**	–9.5	77.1	13.7^*	17.7
	14	77.5	83.4	–4.4	–5.7	195.6	114.6	3.2	1.7	68.5	18.0^*	26.2
	15	157.6	121.8	17.2^*	10.9	—	—	—	—	117.8	–1.7	–1.4
Mean		89.1	87.2	0.03	–2.7	152.2	87.3	–2.7	–2.0	80.2	6.2 ^*	9.0
Total Mean		90,98	89.6	6.7^*	6.4	190.4	99.7	–8.3^**	–3.8	85.7	1.7	2.6

Δ: Strength difference between T1 and T0. % improvement (Δ [T1–T0]/T0 measured strength)^*100. ^*Improvement outside the standard error of measurement (SEM). ^** Worsening outside the SEM.

Table 7

Individual results for knee maximal isometric muscle strength

Participant ID		Extensors				Flexors
		T0 measured strength	% of predicted strength	Δ	% of improvement	T0 measured strength	% of predicted strength	Δ	% of improvement
		(Nm)				(Nm)
Control group	1	128.5	67.7	–14.7^**	–11.4	87.7	95.5	5.3^*	6.0
	2	67.4	49.7	22.5^*	33.4	48.1	74.9	9.4^*	19.5
	3	31.6	24.9	–0.8	–2.5	56.8	94.9	6.4^*	11.2
	4	121.5	58.7	–5.7^**	–4.7	80.7	80.7	11.3^*	14.1
	5	117.2	63.6	48.9^*	41.7	85.4	96.4	26.4^*	30.9
	6	133.3	90.6	10.2^*	7.7	100.4	143.7	–12.8^**	–12.7
	7	137.1	71.1	–8.3^**	–6.0	87.0	93.9	–2.2	–2.6
	8	83.6	57.8	7.0^*	8.4	66.4	96.1	6.6^*	10.0
	9	206.0	126.6	–47.9^**	–23.3	93.7	119.6	16.2^*	17.3
	10	119.6	73.5	–10.6^**	–8.9	67.0	86.0	17.0^*	25.3
Mean		114.6	68.4	0.07	3.4	77.3	98.2	8.4^*	11.9
Device group	11	15.6	9.8	–0.4	–2.8	52.9	69.2	1.3	2.5
	12	80.9	60.6	19.6^*	24.3	56.3	89.4	0.9	1.6
	13	29.0	19.0	1.3^*	4.4	54.9	75.2	–1.5	–2.8
	14	70.8	44.7	10.6^*	15.0	64.0	84.1	10.5^*	16.4
	15	211.4	95.4	–19.6^**	–9.3	17.0	108.7	8.9^*	7.6
Mean		81.5	45.9	2.3^*	6.3	69.0	85.3	4.0^*	5.1
Total Mean	103.6	60.9	0.8	4.4	74.5	93.9	6.9^*	9.6

Δ: Strength difference between T1 and T0. % improvement (Δ [T1-T0]/T0 measured strength)^*100. ^* Improvement outside the standard error of measurement (SEM). ^** Worsening outside the SEM.

Table 8

Individual results for ankle maximal isometric muscle strength

Participant ID		Dorsiflexors
		T0 measured strength	% of predicted strength	Δ	% of improvement
		(Nm)
Control group	1	12.7	29.9	–0.7	–5.4
	2	15.8	48.6	1.1^*	7.1
	3	10.8	34.8	0.4	3.9
	4	21.6	47.2	–0.7	–3.4
	5	28.6	68.3	5.2^*	18.0
	6	22.4	62.6	3.7^*	16.5
	7	29.4	64.8	–1.6^**	–5.5
	8	8.8	27.1	1.0	11.2
	9	23.0	65.8	4.8^*	20.6
	10	9.1	24.0	1.7^*	18.3
Mean		18.2	47.3	1.5^*	8.1
Device group	11	11.4	30.9	1.7^*	15.1
	12	20.9	63.6	–2.9^**	–13.8
	13	6.7	18.6	0.0	0.06
	14	17.7	50.5	–0.1	–0.5
	15	25.9	54.1	4.6^*	17.7
Mean		16.5	43.5	0.7	3.8
Total Mean		17.7	46.1	1.2^*	6.7

Δ: Strength difference between T1 and T0. % improvement (Δ [T1–T0]/T0 measured strength)^*100. ^* Improvement outside the standard error of measurement (SEM). ^** Worsening outside the SEM.

Table 9

Individual number of outcome measures with improvements outside the standard error of measurement

Participant ID		Mobility tests	MIMS tests	Total
		(/6)	(/6)	(/12)
Control group	1	2	3	5
	2	2	4	6
	3	1	1	2
	4	0	2	2
	5	3	3	6
	6	2	4	6
	7	2	2	4
	8	4	2	6
	9	3	2	5
	10	1	5	6
Mean		2.0	2,8	4.8
Device group	11	0	2	2
	12	1	1	2
	13	1	2	3
	14	1	3	4
	15	2	3	5
Mean		1.0	2.2	3.2
Total Mean		1.67	2.60	4.27

RETROSPECTIVE ACCEPTABILITY

Only the results that enrich the quantitative results will be reported. In general, participants found the program successful and it gave them positive feelings and impressions. All participants reported many perceived improvements at the end of the program, including the following: increased energy on a daily basis, increased strength and endurance of the lower limb muscles, decreased ankylosis of the lower limbs, and decreased muscle pain during physical activities. Participants also noted improvements in the accomplishment of activities related to mobility such as walking, using stairs, walking on inclined grounds and picking up an object from the ground. Some participants reported improvements in the accomplishment of activities of daily living such as sweeping the floor.

Questions were asked about the factors that had positive and negative impacts on program adherence. Participants reported the following supporting factors: physiotherapist’s weekly follow-up phone call, period of the year during which the training program took place, feeling of physical well-being brought by being active, trust in the team that developed the program, and simplicity of execution (no special equipment required, short duration of training session, possibility of doing it in different places). Follow-up phone calls by the physiotherapist allowed for an individual progression adapted to the desired level of difficulty, provided follow-up in the event of an injury, had a motivational effect, offered answers to questions and created a sense of security. Participants also stressed the importance of their involvement in the decision-making process regarding the progression of repetitions and/or sets for each exercise. Participants in the device group highlighted the interactive and stimulating benefits of the device when performing the exercises.

However, participants noted barriers to adherence to the home-based training program, including joint and muscle pain and other health issues. Some participants also reported low energy levels, mainly at the end of the day. Participants highlighted the lack of time to perform the exercises because of other activities, such as work, but they didn’t have to give up any other activities to take part in the training program. Participants in the device group noted some barriers related to the device, including the requirement to train only at home (equipment requirement) and technical problems.

Participants noted several advantages to a home-based program, but also a few disadvantages. The main advantages were: suitable environment, possible participation regardless of geographical location, flexible schedule adapted to lifestyle and family responsibilities, no travel, reduced costs, less preparation time and no environmental factors. However, participants reported the following disadvantages: less supervision, limited space, no mutual support and not belonging to a team.

All participants expressed that they would recommend this home-based training program to people with DM1 since it is customizable depending on individual abilities and disease characteristics, and it allows participants to remain active.

DISCUSSION

This study aimed to assess the immediate effects of a 10-week individualized home-based program. To the best of our knowledge, this is the first study that ever tried to determine if the addition of an assistive training device during the home-based training sessions had a significant impact on the improvements, as compared to a program based on semi-supervision by a physiotherapist in DM1. It is also the first study to evaluate the retrospective acceptability of a home-based training program.

Results of the whole cohort at T0 illustrated the high level of variability between participants regarding the percentage of predictive value for the MIMS of the lower limbs, walking speed, balance and abilities to make a sit-to-stand transfer. This heterogeneousness most likely had an impact on the outcomes of the training program. At T0, participants had on average little weakness in the hip muscles, mild to moderate in the knee muscles and more severe in the ankle muscles. These findings are consistent with those obtained by Gagnon et al. (2018), who noted that muscle weakness is progressing from distal to proximal [6]. The performance in mobility activities at T0 and T1 show that participants had difficulty performing the sit-to-stand transfer without using their upper limbs. In fact, their results are similar to those obtained by healthy people over 60 years old [38]. For self-selected walking speed, the average at T0 and T1 are similar to the performance of healthy people over 70 years old [39]. Our results are consistent with the accelerated model of aging proposed by Mateos-Aierdi et al. (2015) for people with the adult form of DM1 [40].

Intention-to-treat analyses revealed no significant differences in every outcome measures for the time effect, group effect and interaction time^*group effects, except for the knee flexor muscles, where a significant improvement was noted between the two assessments. The lack of statistically significant differences does not necessarily mean that there were no effects, but it does means that an effect of zero cannot be rejected [41]. The small sample size, mainly for the device group, clearly limits the power of statistical analyses to detect a significant effect of the training program on the outcomes. These findings are consistent with those obtained by Kierkegaard and al. [42], who noted no significant benefits following the completion of the Friskis&Svettis® Open Doors 14-weeks program by people who had the adult form of DM1 and exhibited mild to moderate muscle weakness. Only few studies have documented the impact of a home-based training program on lower limb muscle strength and activities related to mobility in this population [43, 44]. Lindeman et al. [43, 44], also noted no statistically significant changes on lower muscle strength and activities related to mobility after a 24-week home-based training program with strength weights. However, in Lindeman et al.’s study [44], they documented a significant improvement in muscle endurance. Some studies have documented an improvement in the performance of different activities related to mobility [15 , 46] and maximum muscle strength [15, 45]. Because the methods of intervention vary enormously between studies in terms of level of supervision (group intervention [45], supervised [46], semi-supervised [43, 44]), settings (home [43, 44], rehabilitation center [46], training center), exercise choice (balance [45, 46], strength training [43 , 46], endurance [46]) and intervention parameters (number of weeks [between six [46] to 24 [43, 44] weeks], set, repetition, intensity), it is difficult to compare results between studies. In our study, some participants displayed a lower average strength at the end of the training program. The lower limb muscle groups for which the greatest number of participants had a decrease in strength beyond the SEM at the end of the program are 1) the hip extensors (6/15 participants) and 2) the hip abductors (6/15). For the hip extensors, it is mainly (5/6 participants) people who had a strength value corresponding to a high percentage of their respective predicted value at T0 (range between 104.2% and 141.5%). At T0, the hip extensors were the lower limb muscle group that displayed the highest average percentage of the predicted value (99.75%). Regarding the hip abductors, there is no predictive value, so it is impossible to validate the percentage of the predicted strength at T0. There are methodological challenges related to stabilization when assessing the strength of lower limb muscle groups in very strong participants. For example, participant # 6 exhibited a decrease beyond the SEM in strength for the hip extensors and knee flexors. This is the participant with the highest predicted strength percentage at T0, corresponding to 141.5% and 143.7%, respectively. We also hypothesize that improving strength for a person who initially exhibits strengths greater than their predicted value requires greater volume and intensity than our program. Our home-based program was conducted from September through December. Due to our regional climate, people with DM1 certainly greatly decrease their activity level for this period as compared to the summer period. It is therefore possible that our home-based program cannot compensate for the effects of this seasonal inactivity, mainly for people with less mobility. This loss of strength had also been observed in some participants following a 10-week supervised balance-training program [45]. This loss of strength should be further explored.

In our study, some participants had lower average performance at the end of the program mainly for 30-Second Chair Stand Test and comfortable and maximum walking speeds. Since the execution of the transfer (e.g. sit-to-stand) in the exercise program had to be done slowly in order to ensure the safety and the good quality of the movements, participants may have developed the habit of slowing down the movement to better execute different movement sequences and consequently, obtained a decrease in performance beyond the SEM for the aforementioned functional mobility activities.

Despite the lack of statistically significant im-provements, the majority of participants perceived positive effects and reported mainly changes in the strength and endurance of their lower limb muscles and in various activities related to mobility. It must be noted that significant differences in the results are not the same as clinically important or relevant differences. Because participants individually improved in different outcomes and not necessarily outside the SEM, other factors (such as muscle histological features [15]) could play a role in the hetegerogenous response to exercise observed in DM1. It also highlights the importance of focusing on individual results, and not only on collective results. Indeed, the mean performance of the whole cohort improved outside the SEM for self-selected 10mWT and strength of the hip flexors, knee flexors and dorsiflexors muscle groups. If we look closely at the results, the MIMS of one participant in the control group (ID #4) deteriorated for five of the six muscle groups outside the SEM, including a decrease in strength of 49 Nm for hip extensors, which certainly had a negative impact on the average results of the whole cohort. This participant works in a circus school during the summer and as the project took place from September to December, this deterioration is possibly mainly caused by the change in the level of activity rather than by the exercise program itself.

Adherence is an important issue for home-based training program with the DM1 population, as they tend to have a lack of initiative and motivation as well as apathetic attitudes (1). The adherence rate of the 15 participants who completed the home-based training program is very high (>83 %). This result is similar to the one obtained by Roussel et al. (2020) during a 12-week exercise training program at a sport/fitness center [15]. Various strategies to improve exercise adherence were used in our study, such as weekly follow-up phone calls from the physiotherapist and customization of the training program. In fact, although the primary objective of the follow-up calls was to ensure safety and adequate progression in the number of repetitions and sets for each exercise, participants reported a motivational effect on the continuation of the program. Participants also reported that the flexible schedule greatly helped the implementation of the home-based training program. The strategies put in place seem to have had a positive impact on the training program adherence. The acceptability of the training program by all participants certainly had a positive impact on the adherence rate, as Sekhon et al. [22] had already found. Adding an assistive training device also seems to be a good strategy, since it was well accepted by participants of the device group, who also underlined its stimulating and interactive contribution. Although four participants who dropped out of the study were part of the device group, there seems to be no link between the reasons for dropping out and the training program.

The exercise training program used in our study was simple, safe, feasible and applicable for people with DM1. These are the most important criteria for exercise prescription in similar populations, especially for home-based training program [47]. Our training program included only three simple exercises (short duration) and required no special equipment. Participants indicated that the number of exercises and the duration of the training sessions fostered adherence. When choosing the exercises and the execution speed, we had to take into account the higher risk of falling in this population. In fact, three participants were at high risk of falling at T0 and two participants used a walking aid to move inside their home. The exercises were therefore executed slowly to ensure safety and relied only on the weight of the body itself. This may have had a negative impact on the improvements noted between T0 and T1, since low-intensity resistance training programs have less significant benefits than training performed at higher velocities in concentric movements with moderate-intensity in the elderly population [48].

STUDY LIMITATIONS

The most important limitation in this study is the small sample size. In order to properly document the impact of our home-based training program and explore the effects of adding an assistive training device, it would be essential to conduct a study with a larger sample. Sample selection is also an issue in clinical trials focused on rare diseases. There is a risk of selection bias in intervention studies involving physical exercise. In fact, people who are willing to participate in a study involving a training program are often younger and/or have a better functional level than the whole population [49]. Moreover, all participants were men with the adult form of DM1, which limits generalizations to the whole DM1 population.

CONCLUSION

The study’s findings provide encouraging data on the effects of a home-based training program for people with the adult form of DM1. Although participants reported some disadvantages from training at home, considering the lack of access to transportation in the DM1 population, this intervention seems appropriate to counteract the weakening of muscle strength. The development of periodical home-based training programs for people with DM1 would reduce the financial burden on the health system and also improve the clinical services offered to this population.

DECLARATION OF CONFLICTS OF INTEREST

The authors have no conflict of interest to report.

Footnotes

ACKNOWLEDGMENTS

Study funded by the Regroupement stratégique INTER du Fonds de Recherche du Québec Nature et Technologies and the Natural Sciences and Engineering Research Council of Canada (NSERC). The authors would like to thank all patients who participated in this study. The authors would also like to thank Marie-Pier Roussel and Véronique Tremblay for their implication in the data collection and Marjolaine Tremblay for his help in the qualitative analysis.

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