Perturbation-based balance training of older adults and effects on physiological, cognitive and sociopsychological factors: a secondary analysis from a randomised controlled trial with 12-month follow-up.

BACKGROUND: Perturbation-based balance training (PBT) has shown promising, although diverging, fall-preventive effects; however, the effects on important physical, cognitive and sociopsychological factors are currently unknown. The study aimed to evaluate these effects on PBT at three different time points (post-training, 6-months and 12-months) in community-dwelling older adults compared with regular treadmill walking. METHODS: This was a preplanned secondary analysis from a randomised, controlled trial performed in Aalborg, Denmark, between March 2021 and November 2022. Community-dwelling older adults aged ≥65 were randomly assigned to participate in four sessions (lasting 20 min each) of either PBT (intervention) or regular treadmill walking (control). All participants were assigned to four testing sessions: pretraining, post-training, 6-month follow-up and 12-month follow-up. At these sessions, physical, cognitive and sociopsychological measures were assessed. RESULTS: In total, 140 participants were randomly allocated to either the PBT or control group. Short-term (pretraining to post-training) between-group differences were seen for choice stepping reaction time (-49 ms, 95% CI -80 to -18), dual-task gait speed (0.05 m/s, 95% CI 0.01 to 0.09) favouring the PBT group. However, these improvements were not sustained at the 6-month and 12-month follow-up. No significant between-group differences were found in other physical, cognitive or sociopsychological factors. CONCLUSIONS: This study showed that PBT, in the short term, improved choice stepping reaction time and dual-task gait speed among community-dwelling older adults. Yet, these improvements were not retained for 6- or 12-months. The healthy state of the study's population may have imposed a ceiling effect limiting the ability to show any clinically relevant effects of PBT. TRIAL REGISTRATION NUMBER: NCT04733222.

Effects of treadmill slip and trip perturbation-based balance training on falls in community-dwelling older adults (STABILITY): study protocol for a randomised controlled trial.

INTRODUCTION: Falls among older adults are most frequently caused by slips and trips and can have devastating consequences. Perturbation-based balance training (PBT) have recently shown promising fall preventive effects after even small training dosages. However, the fall preventive effects of PBT delivered on a treadmill are still unknown. Therefore, this parallel-group randomised controlled trial aims to quantify the effects of a four-session treadmill-PBT training intervention on falls compared with treadmill walking among community-dwelling older adults aged 65 years or more. METHODS AND ANALYSIS: 140 community-dwelling older adults will be recruited and randomised into either the treadmill-PBT or the treadmill walking group. Each group will undergo three initial training sessions within a week and an additional 'booster' session after 26 weeks. Participants in the treadmill-PBT group will receive 40 slip and/or trip perturbations induced by accurately timed treadmill belt accelerations at each training session. The primary outcome of interest is daily life fall rates collected using fall calendars for a follow-up period of 52 weeks. Secondary outcomes include physical, cognitive and social-psychological fall-related risk factors and will be collected at the pre-training and post-training test and the 26-week and 52-week follow-up tests. All outcomes will be analysed using the intention-to-treat approach by an external statistician. A Poisson's regressions with bootstrapping, to account for overdispersion, will be used to compare group differences in fall rates. ETHICS AND DISSEMINATION: The study protocol has been approved by the North Denmark Region Committee on Health Research Ethics (N-20200089). The results will be disseminated in peer-reviewed journals and at international conferences. TRIAL REGISTRATION NUMBER: NCT04733222.

Lumbar muscles recruitment during resistance exercise for upper limbs.

The aim of this study was to evaluate the EMG activity of lumbar multifidus (MU), longissimus thoracis (LT) and iliocostalis (IC) muscles during an upper limb resistance exercise (biceps curl). Ten healthy males performed maximal voluntary isometric contraction (MVC) of the trunk extensors, after this, the biceps curl exercise was executed at 25%, 30%, 35% and 40% one repetition maximum during 1 min, with 10 min rest between them. EMG root mean square (RMS) and median frequency (MFreq) were calculated for each lifting and lowering of the bar during the exercise bouts, to calculate slopes and intercepts. The results showed increases in the RMS and decreases in the MFreq slopes. RMS slopes were no different between muscles, indicating similar fatigue process along the exercise irrespective of the load level. MU and LT presented higher RMS irrespective of the load level, which can be related to the specific function during the standing position. On the other hand, IC and MU presented higher MFreq intercepts compared to LT, demonstrating possible differences in the muscle fiber conduction velocity of these muscles. These findings suggest that trunk muscles are differently activate during upper limb exercises, and the fatigue process affects the lumbar muscles similarly.

Heavy-intensity aerobic exercise affects the isokinetic torque and functional but not conventional hamstrings:quadriceps ratios.

Running exercises are frequently related to muscular injuries, which may be a result of muscular imbalance. The present study aimed to verify the effects of heavy-intensity continuous running exercise on the functional and conventional hamstrings:quadriceps ratios, and also in the knee flexors and extensors EMG activity in active non-athletic individuals. Sixteen active males performed maximal isokinetic concentric and eccentric knee flexions and extensions at 60 degrees s(-1) and 180 degrees s(-1). In another session, the same procedure was conducted after a continuous running exercise at 95% onset of blood lactate accumulation. Torque and electromyographic ratios were calculated from peak torque and integrated electromyographic activity (knee flexor and extensors). Creatine kinase was measured before and 24h after running exercise. Eccentric torque (knee flexion and extension) decreased significantly after running only at 180 degrees s(-1) (p<0.05). No differences were found for the conventional torque ratios (p>0.05), however, the functional torque ratios at 180 degrees s(-1) decreased significantly after running (p<0.05). No effects on the electromyographic activity and electromyographic ratios were found (p>0.05). Creatine kinase increased slightly 24 h after running (p<0.05). Heavy-intensity continuous running exercise decreased knee flexor and extensor eccentric torque, and functional torque ratios under fast velocities (180 degrees s(-1)), probably as result of peripheral fatigue.

EMG amplitude and frequency parameters of muscular activity: effect of resistance training based on electromyographic fatigue threshold.

The present study aimed to evaluate the effect of a resistance training program based on the electromyographic fatigue threshold (EMG(FT), defined as the highest exercise intensity performed without EMG alterations), on the EMG amplitude (root mean square, RMS) and frequency (median frequency, MF) values for biceps brachii (BB), brachioradialis (BR), triceps brachii (TB) and multifidus (MT). Twenty healthy male subjects, (training group [TG], n=10; control group [CG], n=10), firstly performed isometric contractions, and after this, dynamic biceps curl at four different loads to determine the EMG(FT). The TG training program used the BB EMG(FT) value (8 weeks, 2 sessions/week, 3 exhaustive bouts/session, 2 min rest between bouts). No significant differences were found for the isometric force after the training. The linear regression slopes of the RMS with time during the biceps curl presented significant decrease after training for the BB, BR and TB muscles. For the MT muscle, the slope and MF intercept values changed with training. The training program based on the EMG(FT) influenced EMG the amplitude more than EMG frequency, possibly related to the recruitment patterns of the muscles, although the trunk extensor muscles presented changes in the frequency parameter, showing adaptation to the training program.

Electromyographic analisys of biceps brachii and erector spinae muscles before and after a fatiguing dynamic test / Análise eletromiográfica dos músculos bíceps do braço e eretores da espinha antes e após um teste isotônico fadigante

The increased number of musculoskeletal injuries can be caused by the lack attention to load level, as well as the posture and time of execution of an overloaded exercise. This way, the objective of this study was to analyze the effect of repetitive barbell biceps curl exercise over biceps brachii and erector spinae muscle electromyographic parameters. Ten healthy male subjects (20,91±1,37 years), without musculoskeletal diseases, performed the biceps curl exercise until fatigue, with 25%, 35% and 45% of 1 repetition maximum. The electromyographic activity of biceps brachii and erector spinae muscles was analyzed during isometric contraction performed before and immediately after fatiguing tests. The muscular fatigue was identified through the increase of root mean square and decrease of median frequency during isometric contractions. The results demonstrated these characteristics of fatigue after fatiguing test (p<0,05) for both muscles, showing a relationship time-load dependent for these electromyographic parameters. No significant differences were found between left and right muscles in the parameters analyzed. The experimental procedures allowed identify the muscular fatigue on biceps brachii muscles and erector spinae activity during barbell biceps curl and the dependence with load and number of repetition...