Reliability of the accelerometer to control the effects of physical activity in older adults

Background

Reliable physical activity measurements in community-dwelling older adults are important to determine effects of targeted health promotion interventions. Many exercise interventions aim to improve time spent sedentary (SED), in light-intensity-physical-activity (LPA) and moderate-to-vigorous-intensity-physical-activity (MVPA), since these parameters have independently proposed associations with health and longevity. However, many previous studies rely on self-reports which have lower validity compared to accelerometer measured physical activity patterns. In addition, separating intervention-effects from reactivity measurements requires sufficient test-retest reliability for accelerometer assessments, which is lacking in older adults.

Objectives

The study objective was to investigate the reliability of sensor-based PA-patterns in community-dwelling older adults. Furthermore, to investigate change over time of physical activity patterns and examine any compensatory-effect from the eight-week supervised exercise-intervention.

Methods

An exercise-group (n = 78, age-range:65-91yrs) performed two 1h-exercise sessions/week during eight-weeks. PA-pattern was assessed (using hip-worn accelerometers), twice before and once during the last-week of the intervention. A control-group (n = 43, age-range:65-88yrs) performed one pre-test and the end-test with no exercise-intervention. A dependent-t-test, mean-difference (95%-CI), limits-of-agreement and intraclass-correlation-coefficient-ICC were used between the two pre-tests. Repeated-measures-ANOVA were used to analyze any intervention-effects.

Results

The exercise-groups´ two pre-tests showed generally no systematic change in any PA- or SED-parameter (ICC ranged 0.75–0.90). Compared to the control group, the exercise intervention significantly (time x group-interaction, p<0.05) increased total-PA-cpm (exercise-group/control-group +17%/+7%) and MVPA-min/week (+41/-2min) and decreased %-of-wear-time for SED-total (-4.7%/-2.7%) and SED-bouts (-5.7%/-1.8%), and SED-bouts min/d (-46/-16min). At baseline level, no significant differences were found between the two groups for any parameter.

Conclusions

The current study presents a good test-retest-reliability of sensor-based-one-week-assessed-PA-pattern in older-adults. Participating in an 8-week supervised exercise intervention improved some physical activity and sedentary parameters compared to the control group. No compensatory-effect was noted in the intervention-group i.e., no decrease in any PA-parameter or increase in SED at End-test (in %-of-wear-time, min/day or total-PA).

Improving Strength, Power, Muscle Aerobic Capacity, and Glucose Tolerance through Short-term Progressive Strength Training Among Elderly People

This protocol describes the simultaneous use of a broad span of methods to examine muscle aerobic capacity, glucose tolerance, strength, and power in elderly people performing short-term resistance training (RET). Supervised progressive resistance training for 1 h three times a week over 8 weeks was performed by RET participants (71±1 years, range 65-80). Compared to a control group without training, the RET showed improvements on the measures used to indicate strength, power, glucose tolerance, and several parameters of muscle aerobic capacity. Strength training was performed in a gym with only robust fitness equipment. An isokinetic dynamometer for knee extensor strength permitted the measurement of concentric, eccentric, and static strength, which increased for the RET group (8-12% post- versus pre-test). The power (rate of force development, RFD) at the initial 0-30 ms also showed an increase for the RET group (52%). A glucose tolerance test with frequent blood glucose measurements showed improvements only for the RET group in terms of blood glucose values after 2 h (14%) and the area under the curve (21%). The blood lipid profile also improved (8%). From muscle biopsy samples prepared using histochemistry, the amount of fiber type IIa increased, and a trend towards a decrease in IIx in the RET group reflected a change to a more oxidative profile in terms of fiber composition. Western blot (to determine the protein content related to the signaling for muscle protein synthesis) showed a rise of 69% in both Akt and mTOR in the RET group; this also showed an increase in mitochondrial proteins for OXPHOS complex II and citrate synthase (both ~30%) and for complex IV (90%), in only the RET group. We demonstrate that this type of progressive resistance training offers various improvements (e.g., strength, power, aerobic capacity, glucose tolerance, and plasma lipid profile).

Reassessment of the putative role of BLK-p.A71T loss-of-function mutation in MODY and type 2 diabetes

AIMS/HYPOTHESIS

MODY is believed to be caused by at least 13 different genes. Five rare mutations at the BLK locus, including only one non-synonymous p.A71T variant, were reported to segregate with diabetes in three MODY families. The p.A71T mutation was shown to abolish the enhancing effect of BLK on insulin content and secretion from pancreatic beta cell lines. Here, we reassessed the contribution of BLK to MODY and tested the effect of BLK-p.A71T on type 2 diabetes risk and variations in related traits.

METHODS

BLK was sequenced in 64 unelucidated MODY samples. The BLK-p.A71T variant was genotyped in a French type 2 diabetes case-control study including 4,901 cases and 4,280 controls, and in the DESIR (Data from an Epidemiological Study on the Insulin Resistance Syndrome) and SUVIMAX (Supplementation en Vitamines et Mineraux Antioxydants) population-based cohorts (n = 6,905). The variant effects were assessed by logistic and linear regression models.

RESULTS

No rare non-synonymous BLK mutations were found in the MODY patients. The BLK p.A71T mutation was present in 52 normoglycaemic individuals, making it very unlikely that this loss-of-function mutation causes highly penetrant MODY. We found a nominal association between this variant and increased type 2 diabetes risk, with an enrichment of the mutation in the obese diabetic patients, although no significant association with BMI was identified.

CONCLUSIONS/INTERPRETATION

No mutation in BLK was found in our MODY cohort. From our findings, the BLK-p.A71T mutation may weakly influence type 2 diabetes risk in the context of obesity; however, this will require further validation.

Maximal aerobic power versus performance in two aerobic endurance tests among young and old adults

BACKGROUND

Aerobic fitness is of great value for reducing risk of mortality and cardiovascular diseases.

OBJECTIVE

This study evaluated the performance in and correlations between a new test (five-minute pyramid test, 5MPT), the six-minute walk-test (6MWT) and maximal oxygen uptake (VO2max) among old and young adults.

METHODS

Forty-four habitually active adults (females and males), 23 old (64-79 years) and 21 young (20-32 years) participated. In the 5MPT, the participants moved back and forth along a short walkway (5.5 m) over boxes (height: 'old people' 0.42 m, 'young people' 0.62 m) arranged like an elongated step pyramid for 5 min. Power in the pyramid test (5MPT(power)) was calculated as the product of numbers of laps, body weight, gravity and highest box level divided by time. A 6MWT and a maximal cycle ergometer test for direct measurements of VO2max were also performed. In all tests heart rate, with on-line electrocardiography, and perceived exertion were recorded.

RESULTS

There was a strong correlation between the 5MPT(power) and VO2max for the entire group studied (r = 0.98), and each of the four subgroups old and young females and males separately (r = 0.78-0.98). Contrary to several earlier studies, especially involving people with various diseases, the present data showed that 6MWT cannot be used to predict VO2max among old females and young adults. The correlation with VO2max was weaker for the 6MWT than for the 5MPT(power). The relative performance values for the old compared to the young (ratio old/young × 100) were considerably lower in 5MPT(power) and VO2max (47-55%) than in distance and 'work' in the 6MWT (82-86%).

CONCLUSIONS

The results, with age and gender variations, can be valuable information in health-fitness contexts, since measuring physical aerobic capacity is very significant in connection with risk evaluations of mortality and various diseases. The 5MPT is a rapid, functional, easy and inexpensive tool for predicting assessed maximal aerobic power.

Type 2 diabetes risk alleles near ADCY5, CDKAL1 and HHEX-IDE are associated with reduced birthweight

AIMS/HYPOTHESIS

The fetal insulin hypothesis suggests that variation in the fetal genotype influencing insulin secretion or action may predispose to low birthweight and type 2 diabetes. We examined associations between 25 confirmed type 2 diabetes risk variants and birthweight in individuals from the Danish Inter99 population and in meta-analyses including Inter99 data and reported studies.

METHODS

Midwife records from the Danish State Archives provided information on mother's age and parity, as well as birthweight, length at birth and prematurity of the newborn in 4,744 individuals of the population-based Inter99 study. We genotyped 25 risk alleles showing genome-wide associations with type 2 diabetes.

RESULTS

Birthweight was inversely associated with the type 2 diabetes risk alleles of ADCY5 rs11708067 (beta = -33 g [95% CI -55, -10], p = 0.004) and CDKAL1 rs7756992 (beta = -22 g [95% CI -43, -1], p = 0.04). The association for the latter locus was confirmed in a meta-analysis (n = 24,885) (beta = -20 g [95% CI -29, -11], p = 5 x 10(-6)). The HHEX-IDE rs1111875 variant showed no significant association among Danes (p = 0.09); however, in a meta-analysis (n = 25,164) this type 2 diabetes risk allele was associated with lower birthweight (beta = -16 g [95% CI -24, -8], p = 8 x 10(-5)). On average, individuals with high genetic risk (>or=25 type 2 diabetes risk alleles) weighed marginally less at birth than those with low genetic risk (<25 type 2 diabetes risk alleles) (beta = -35 g [95% CI -69, -2], p = 0.037).

CONCLUSIONS/INTERPRETATION

We report a novel association between the fetal ADCY5 type 2 diabetes risk allele and decreased birthweight, and confirm in meta-analyses associations between decreased birthweight and the type 2 diabetes risk alleles of HHEX-IDE and CDKAL1. No strong general effect on birthweight can be ascribed to the 25 common type 2 diabetes risk alleles.

Specific phase related patterns of trunk muscle activation during lateral lifting and lowering

AIM

Lateral bending of the trunk has been demonstrated to be a risk factor in connection with injuries to the spine and its surrounding tissues. Adequate co-ordination of muscle controlling movement and stabilization of the trunk is essential to avoid injury. However, little is yet known about the responses of the lumbar trunk muscles during lateral lifting and lowering. The present investigation was therefore designed to study these responses.

METHODS

In six subjects performing lateral lifting and lowering of different loads (0-40 kg) held laterally in one hand, the activities of eight trunk muscles were recorded using intramuscular electrodes. In addition, the angular motion of the trunk from side to side was measured from video recordings. Electromyographic amplitudes on both the contra- and ipsi-lateral sides (ipsi = towards the loaded hand) were analysed in relation to defined phases of trunk motion.

RESULTS

Three periods of trunk muscle activation were generally observed, two from the contralateral muscles at the beginning and end of the motion and one from the ipsilateral muscles during the mid-part of the motion. The activities of the contralateral muscles increased, whereas the activities of the ipsilateral muscles decreased with increasing load. The degree of bilateral co-activation was greater in ventral than in dorsal muscles, in lowering compared with lifting, and in no-load or low-load compared with heavy load conditions.

CONCLUSION

The co-ordination of trunk muscle activations during side-to-side trunk movements is dependent on trunk position and load. It is speculated that ventral muscles, particularly the oblique and transverse abdominal muscles, are relatively more involved than the other trunk muscles in trunk stabilization, especially in connection with lowering of a light hand-held load.

Diverging intramuscular activity patterns in back and abdominal muscles during trunk rotation

STUDY DESIGN

An intramuscular electromyographic study was performed on trunk rotations during sitting and standing.

OBJECTIVE

The aim was to provide new information on activation levels for deep trunk muscles in various unresisted and resisted trunk rotations.

SUMMARY AND BACKGROUND DATA

Frequent daily trunk twisting and decreased maximal strength during trunk rotation have been associated with low back pain or sciatic pain. However, the involvement of deep trunk muscles during different trunk rotations is relatively unknown.

METHODS

Ten healthy subjects participated. Fine-wire electrodes were inserted, under ultrasound guidance, into psoas, quadratus lumborum, the superficial medial lumbar erector spinae (ES-s, multifidus) and its deep lateral portion (ES-d, iliocostalis), iliacus, rectus abdominis, obliquus externus, and obliquus internus.

RESULTS

The highest involvement for all muscles was observed on the ipsilateral side, in maximal trunk twists with shoulder resistance, except obliquus externus, which showed a dominant contralateral side, and rectus abdominis, which was little activated in all rotations. In contrast, maximal trunk twist without shoulder resistance, i.e., freely performed, resulted generally in lower levels for all muscles involved and in a shift of side dominance for the lumbar muscles quadratus lumborum, psoas, and ES-s.

CONCLUSIONS

During trunk rotations the activity patterns for various trunk muscles could drastically change, and even be the opposite, between the two body sides, within the same type of task, depending on several factors such as initial position, effort level, sitting or standing, and external shoulder resistance.

Relative EMG levels in training exercises for abdominal and hip flexor muscles

The main purpose of our study was to compare systematically EMG levels in sub-maximal training exercises for the trunk and hip flexor muscles with those voluntarily attainable in corresponding situations. Six healthy subjects performed three types of standardized training exercises, whose static positions, movement velocity and range of motion were reproduced during maximal voluntary isokinetic strength tests. EMG was recorded with wire electrodes from the iliacus muscle and with surface electrodes from the rectus femoris, sartorius, rectus abdominis, obliquus externus and internus muscles. The relative EMG values demonstrated a task dependency which could differ between individual muscles. The maximal voluntary activation levels were relatively constant across conditions. Exceptions were present, particularly for the rectus femoris and iliacus muscles. These findings highlight the consequences of using different methods of normalizing EMG. The relative EMG values presented may serve as guidelines when selecting training exercises for specific trunk and hip flexor muscles in sports and rehabilitation.

Relations in families with a mentally retarded child from the perspective of the siblings

Nowadays most handicapped children in Sweden live with their families. In this study some of the consequences of the normalisation of their lives are analysed, focusing on young siblings of mentally retarded children. Sixteen siblings, aged 5-11, were tested with the Family Relations Test and Kvebaek Family Sculpture Technique, as were siblings in a control group in which each child was chosen to match a sibling in the target group with respect to age and family constellation. The results show few differences between the two groups. According to the Family Relations Test, however, the emotional involvement in the eldest non-retarded sibling differs statistically significant from that of the corresponding child in the control group and especially so with respect to negative incoming feelings. Young siblings also show a tendency to unconsciously place the mentally retarded child at larger distances from themselves than they place the other siblings with respect to the Kvebaek Family Sculpture Technique. The results indicate that siblings of mentally retarded children have another frame of reference when judging family relations compared with that of the children in the control group. Thus siblings of mentally retarded children seem to adapt to change in the family because of the mentally retarded child and qualitatively alter their thinking in relation to the family members.

Intramuscular EMG from the hip flexor muscles during human locomotion

The purpose was to investigate the activation pattern of five major hip flexor muscles and its adaptation to changing speed and mode of progression. A total of 11 healthy subjects performed walking and running on a motor-driven treadmill at speeds ranging from 1.0 to 6.0 m s-1. Intramuscular fine-wire electrodes were used to record myoelectric signals from the iliacus, psoas, sartorius, rectus femoris and tensor fascia latae muscles. The basic pattern, with respect to number of activation periods, remained the same irrespective of speed and mode of progression. However, differences in the relative duration and timing of onset of activation occurred between individual muscles. Over the speed range in walking, a progressively earlier onset was generally seen for the activation period related to hip flexion. Changes in EMG amplitude were measured in the iliacus and psoas muscles and showed a marked increase and difference between walking and running at speeds above 2.0 m s-1. Thus, the alternating flexion-extension movements at the hip during locomotion appear to be governed by a rather fixed 'neural program' which normally only needs minor modulations to accomplish the adjustments accompanying an increase in speed of progression as well as a change from walking to running.

Abdominal and hip flexor muscle activation during various training exercises

The purpose of this study was to provide objective information on the involvement of different abdominal and hip flexor muscles during various types of common training exercises used in rehabilitation and sport. Six healthy male subjects performed altogether 38 different static and dynamic training exercises trunk and hip flexion sit-ups, with various combinations of leg position and support, and bi- and unilateral leg lifts. Myoelectric activity was recorded with surface electrodes from the rectus abdominis, obliquus externus, obliquus internus, rectus femoris, and sartorius muscles and with indwelling fine-wire electrodes from the iliacus muscle. The mean electromyogram amplitude, normalised to the highest observed value, was compared between static and dynamic exercises separately. The hip flexors were highly activated only in exercises involving hip flexion, either lifting the whole upper body or the legs. In contrast, the abdominal muscles showed marked activation both during trunk and hip flexion sit-ups. In hip flexion sit-ups, flexed and supported legs increased hip flexor activation, whereas such modifications did not generally alter the activation level of the abdominals. Bilateral, but not unilateral, leg lifts required activation of abdominal muscles. In trunk flexion sit-ups an increased activation of the abdominal muscles was observed with increased flexion angle, whereas the opposite was true for hip flexion sit-ups. Bilateral leg lifts resulted in higher activity levels than hip flexion sit-ups for the iliacus and sartorius muscles, while the opposite was true for rectus femoris muscles. These data could serve as a basis for improving the design and specificity of test and training exercises.

EMG activities of the quadratus lumborum and erector spinae muscles during flexion-relaxation and other motor tasks

OBJECTIVE: The aim of this study was to provide new information on the myoelectrical activation of the quadratus lumborum, the deep lateral and the superficial medial lumbar erector spinae, the psoas, and the iliacus muscles in various motor tasks. DESIGN: An intramuscular electromyographic study was performed. BACKGROUND: The contribution of individual deep trunk muscles to the stability of the lumbar spine is relatively unknown in different tasks, including the flexion-relaxation phenomenon. METHODS: Seven healthy subjects participated. Fine-wire electrodes were inserted with a needle guided by ultrasound. RESULTS: The highest activity observed for quadratus lumborum and deep lateral erector spinae occurred in ipsilateral trunk flexion in a side-lying position and for superficial medial erector spinae during bilateral leg lift in a prone position. Quadratus lumborum and deep lateral erector spinae were activated when the flexion-relaxation phenomenon was present for superficial medial erector spinae, i.e. when its activity ceased in the latter part of full forward flexion of the trunk, held relaxed and kyphotic. CONCLUSIONS: In general, the activation of the investigated muscles showed a high degree of task specificity, where activation of a certain muscle was not always predictable from its anatomical arrangement and mechanical advantage.