[ad_1]
Study design
This comparative effectiveness study employed an experimental design using randomised group allocations using an online random number generator. There were no predetermined number of participants for each age category, therefore allocation into age groups was only determined by when the volunteers signed up to the study.
To account for lack of familiarity with equipment, exercises, or tests, the initial session was dedicated to familiarisation. During this session, participants were introduced to the equipment, exercises, and tests they would be required to participate in during the study. Except for the 1RM, which were performed to voluntary volition on both occasions, all other exercise was performed at a moderate intensity.
Strength-to-mass ratio provides a valuable and nuanced perspective into the adaptations that extends beyond absolute strength improvements. Given its relevance to the individual’s body weight, it serves as an indicator of how low-dose RT may influence everyday physical tasks and activities of daily living (ADLs) in untrained individuals, highlighting the potential impact of participating in such an exercise program.
Study population
Ethical approval was granted from Northumbria University (Approval ID: 3062). Participants aged 30–60 years old (mean age, 42 ± 7 years) were recruited from the local area using social media, word of mouth, emails, and community groups. Prior to their first session, all participants received participant information sheets outlining the study, informed consent forms, and health-screening forms. Participants were advised to not begin any additional RT once the intervention had begun. Table 1 outlines the characteristics of the participants prior to the intervention.
Inclusion criteria
Participants were eligible if they were between 30-60 years old, uninjured, had no cardiovascular or neuromuscular conditions, and had not participated in lower-limb RT in the previous 6 months.
Exclusion criteria
Participants were excluded if they had either taken part in any lower-limb RT in the last 6 months, had underlying health condition(s) that prevented them from participating in RT, or regularly met or exceeded the UK recommended PA guideline of 150-minutes of moderate to intense PA per week.
Randomisation procedure
In the order of their registration, participants were assigned into their respective age categories (30–39 [n = 10], 40–49 [n = 7], 50–59 [n = 3]). Participants were then randomly assigned to either MI or CT training groups. Randomisation was conducted using an online random number generator. Due to limited participants (20), it was not feasible to analyse age-specific training responses. Participants were blinded to the alternative RT modality.
Interventions
This study compared MI and CT RT modalities using a unilateral leg press (Perform Better Ltd., Warwickshire, UK). All participants began testing and training sessions with a 10-minute cycling warmup (Wattbike Ltd., Nottingham, UK). The rate of perceived exertion (RPE) scale was employed to monitor and standardise warmup intensity; Participants were granted autonomy to self-select resistance and cadence, with the objective of reaching an RPE of at least 7 at the conclusion of the 10-minute warm up [64, 65]. The study consisted of nine sessions, including two pre-intervention testing sessions in accordance with research by Levinger, Goodman [66], who found in untrained participants, two testing sessions were required to determine a sufficient one-repetition maximum (1RM). The best results from either testing sessions were used for each outcome. Following pre-intervention testing, participants attended one weekly training session for 6 weeks, followed by one post-intervention testing session. Where possible, participants were encouraged to attend their sessions at the same time of the week.
Whilst evidence exists to support single-set exercise improving strength, multi-set exercise still offers significantly superior benefits over single-set in both trained and untrained populations [67]. Therefore, during the training sessions, participants performed two warm up sets of five repetitions on the leg press at 40 and 50% 1RM, then five sets of five repetitions at 60% 1RM. The selected intensity of 60% was chosen as that has been shown to reflect the relative effort at the knee joint needed for both young and older adults when performing actives of daily living such as ascending and descending stairs, and rising from a chair [68]. Both groups were instructed to control the eccentric phase of the leg press over three-seconds. The interventions differed only during the concentric phase, with both groups following a metronome app [69], that controlled the eccentric phase to three-seconds. The MI group was instructed and encouraged to deliberately commit to exerting maximal effort and force during the concentric phase of the leg press with the intention of achieving the greatest velocity possible, while the CT group followed the metronome for both eccentric and concentric phases. To assist with standardisation and minimise variability in movement patterns, both groups were supported by a metronome (during both concentric and eccentric phases of the CT group, and only during the eccentric phase of the MI group), as well as a large colour-display that indicated concentric and eccentric phases, verbal guidance from a smartphone app, and verbal encouragement specific to their training group from the supervising researcher.
Outcome measures
Body mass
Body mass was measured using a calibrated weighing scale (Seca 704 s, GmBH & Co Kg, Hamburg, Germany) to ensure consistency, participants were weighed at the same time of day.
Strength-to-mass ratio
Strength-to-mass was calculated by dividing the individuals leg press 1RM by their body mass.
Balance
Balance was assessed using a calibrated balance system (Biodex Balance System™, Biodex Medical Inc., New York, USA). After one trial set, three 20-second tests were performed using the Testing > Postural Stability pre-set. Based on pilot testing, a platform setting of six was selected as it was deemed repeatable enough without exposing participants to the greater risk of injury that may occur at more difficult platform settings. During the tests, balance overall (BalanceO) scores, as well as anterior-posterior (BalanceAP), and medial-lateral (BalanceML) scores, were recorded. All testing was performed on two legs (bipedal balance).
6-minute walk test (6MWT)
Participants were asked to walk and turn on a 30-m distance at a brisk walking pace on an indoor running track for 6 minutes. Participants were blinded to time-remaining and without any verbal encouragement, to better represent their natural gait speed. Distance travelled was recorded in metres.
30-second sit-to-stand (STS)
Participants were asked to sit on a chair with a solid back and arm rests, as recommended by the Centers for Disease Control and Prevention (CDC) [70], with their arms crossed over their chest and feet flat on the floor throughout the test (to avoid ‘rocking’). Participants were asked to perform as many repetitions from a seated to standing position as possible in 30 seconds.
Timed up and go (TUG)
Participants were encouraged to rise from the same chair as the STS, with arms crossed over their chest, and to walk as quickly as possible around a marked position three metres in front of the chair. Both clockwise (TUGc) and anticlockwise (TUGa) directions were attempted with a one-minute rest in between, and the direction attempted first was randomised at each testing session. Time was recorded from the moment the participants weight left the chair to when it was placed back on.
Leg press one-repetition maximum (1RM)
Participants were taken through a progressive warmup which allowed for discussion and practise of minimum knee flexion (90°) to be considered a standardised repetition [71, 72]. Participants were encouraged to hold onto the handles to anchor themselves into the chair, to brace, and were asked to maintain contact with their head, shoulders, back, and pelvis against the chair during the repetitions. Weight lifted was progressed in lower increments as the participant began reaching their 1RM.
Recovery between attempts was standardised to two-minutes, with the aim of a 1RM to be achieved within eight or fewer sets in coordination with research that reviewed trained individuals may get a 1RM within three to five repetitions [73], therefore flexibility was given as participants were untrained. Testing ended when participants either reached their 1RM or failed two consecutive attempts, in which case the previous successful lift was recorded. All testing and training were conducted unilaterally.
Statistical analysis
Data are presented as mean ± SD. Statistical analysis was performed using the SPSS Statistics (v26.0, IBM Corp., Chicago, IL). G*Power [74] was used to determine sample size using effect size of 0.5, alpha at 0.05, and power at 0.8, for a two-group design with two measurements “ANOVA: Repeated measures, within-between interaction.” Assuming moderate correlation among measures (0.5) and sphericity (nonsphericity correction of 1), G*Power calculated a need for 12 participants per group. Testing for normality was conducted on all dependent variables and Shapiro-Wilk’s output was used due to the small sample size [75], and where any dependent variable departed significantly from normality, visual examination of the histogram and QQ plot took place before any further parametric tests were conducted. The five assumptions of a two-way ANOVA were also checked before further analysis was conducted [76]; Mauchly’s test of sphericity was not reported as no within-subject factor had more than two (pre- and post-intervention) categories (timepoints). A two-sample t-test was then conducted to analyse differences in baseline values, and a 2 × 2 two-way repeated-measures ANOVA was used to analyse the effect of the two training modalities (MI vs. CT) over two timepoints (pre- and post-intervention), with p ≤ 0.05 deemed to be statistically significant. As previously mentioned with 20 participants of whom only two were men, age and sex differences could not be partitioned. Effect sizes were calculated using Cohen’s D (where > 0.2: trivial, 0.2 – < 0.5: small, 0.5 – < 0.8: moderate, > 0.8: large magnitude difference [77]), and observed power is denoted as P (obs). Partial Eta-squared (ηp2) values are reported for main effects and overall interactions representing small (0.01 ≤ ηp2 < 0.06), medium (0.06 ≤ ηp2 < 0.14) and large (ηp2 ≥ 0.14) magnitudes of change. If an interaction effect was found, due to small sample size, a Bonferroni post-hoc test was chosen to find where the differences were present. To assess 1RM reliability across the two pre-intervention tests, both the Intraclass Correlation Coefficient (ICC) and Coefficient of Variation (CV%) were calculated. The ICC was determined using a Two-Way Random model with Absolute Agreement, using SPSS Statistics (v26.0, IBM Corp., Chicago, IL). The CV% was calculated using the formula (Standard Deviation / Mean) * 100 on Microsoft Excel (v2312, Microsoft Corporation, Redmond, WA).
Qualitative analysis
To better understand participants’ perceptions of the training and its impact on their QoL, FC, and strength, a focus group was conducted. All participants were invited to attend a focus group sessions held at the Sport Science facilities at Northumbria University, with those unable to attend in-person offered to join online. The aim was to gather detailed feedback of the participants’ experience with their respective intervention. Those unable to attend in-person or online were provided the same set of open-ended questions, curated by the research lead and primary investigator (Appendix 1), with the scope of fostering in-depth discussions about the individual protocols perceived effectiveness, applicability, and impact on participants’ overall health and wellbeing. The entirety of the focus group, both in-person and online was recorded (with participants’ consent). Subsequently, the recordings were transcribed verbatim by the research lead, utilising Google Text-to-Speech (v0.2.7, Alphabet Inc., California, U.S.), supplemented by manual transcription.
Thematic analysis was then carried out to review the transcripts to identify codes highlighting recurring words, phrases, and sentiments; broader themes were then derived from these codes to gather the overall experiences and outcomes reported by the participants. After independent analysis, findings were discussed with the primary investigator. Any discrepancies or disagreements between reviewers were resolved through consultation of a third reviewer. Parentheses indicate participant ID and RT modality.
[ad_2]
Source link
