Accelerometry-based method for assessing energy expenditure in patients with diabetes during walking.

BACKGROUND: Monitoring activity-related energy expenditure (EE) is essential in the management of daily activity and the dietary programme in patients with type 2 diabetes (T2D) and must be estimated accurately. Accelerometry-based equations have frequently used to estimate EE, although the validity of these methods has not been confirmed in patients with T2D. The present study aimed to test the validity of an accelerometry-based method (Bouten's method) to assess EE during walking in patients with T2D. METHODS: The study included 20 patients with controlled T2D [mean (SD) duration: 10.6 (6.1) years; age: 57.5 (8.4) years; body mass index: 26.4 (2.6) kg m- ²]. All participants performed five 6-min periods of walking at different speeds (0.5-1.5 m s-1 ) on a treadmill. Mechanical data were recorded using an inertial measurement unit placed on the lower back with gas exchange being simultaneously monitored. RESULTS: Values of EE during walking estimated by the accelerometer method did not differ significantly from those measured by indirect calorimetry. Bias and root mean square error were -1.17 and 2.93 kJ min-1 , respectively, on average across speeds. CONCLUSIONS: Our results suggest that EE during walking may be accurately estimated in patients with diabetes mellitus using an accelerometer.

Horizontal body and trunk center of mass offset and standing balance in scoliotic girls.

In adolescent idiopathic scoliotic girls, postural imbalance is attributed to a sensory rearrangement of the motor system on the representation of the body in space. The objectives of this study were to test if the anteroposterior (AP), mediolateral (ML) and resultant body-head and trunk center of mass (COM) horizontal offsets were similar in able-bodied and scoliotic girls and if these offsets were related to the center of pressure displacements. A total of 21 adolescent idiopathic scoliosis girls and 20 able-bodied girls participated in this study. Their body COM position and that of the head and trunk were estimated according to Damavandi et al. (Med Eng Phys 31:1187-1194, 2009). The COP range and speed in both AP and ML axes were calculated from force plate measurements in quiet standing. The AP offset of the able-bodied group was anterior to the body COM by 11.0 ± 15.9 mm, while that of the scoliotic group was posterior to it by -17.3 ± 11.2 mm. The able-bodied group maintained their head-trunk segment COM more to the right by 14.1 ± 13.1 mm, while that of the scoliotic group was nearly over their body centerline. The scoliotic girls presented higher values for COP range and COP speed than the able-bodied girls. The resultant COM offset was correlated with both the ML COP range and speed only for the scoliotic girls. The small ML COM offset in the scoliotic girls was attributed to a compensatory action of the spinal deformity in the frontal plane resulting in a backward resultant COM offset to regain postural balance concomitant to an increase in the ML neuromuscular demand.

The influence of variable resistance moment arm on knee extensor performance.

To enhance muscular strength, resistance training machines with a cam, incorporating a variable resistance moment arm, are widely used. However, little information is available about the influence of the variable resistance moment arm on torque, velocity, and power during muscle contraction. To address this, a knee extensor machine was equipped with a cam or with a semi-circular pulley that imposed a variable or a constant resistance moment arm, respectively. Fourteen physically active men performed two full knee extensions against loads of 40-80 kg in both conditions. Participants developed significantly higher torque with the pulley than with the cam (P < 0.001). The relative differences between pulley and cam conditions across all loads ranged from 8.72% to 19.87% (P < 0.001). Average knee extension velocity was significantly higher in the cam condition than in the pulley condition. No differences were observed in average and peak power, except at 50 and 55 kg. Torque-velocity and power-velocity relationships were modified when the resistance moment arm was changed. In conclusion, whatever the link, namely cam or pulley, the participants produced similar power at each load. However, the torque-velocity and power-velocity relationships were different in the cam and pulley conditions. The results further suggest that the influence of the machine's mechanism on muscular performance has to be known when prescribing resistance exercises.

The eccentric muscle loading influences the pacing strategies during repeated downhill sprint intervals.

The purpose was to compare self-chosen pace during ten repetitions of 60 m running sprints performed on a level surface (SPL), or when running uphill (SPU) or downhill (SPD) on a 4.7% slope. When expressed as percent of maximal running speed for corresponding condition, SPD was lower than SPL (95.28 +/- 1.93 vs. 97.31 +/- 1.29%; P = 0.044), which was lower than SPU (97.31 +/- 1.29 vs. 98.09 +/- 0.74%; P = 0.026). Heart rates, blood lactate concentrations and general perceived exertion were lower during SPD (163.8 +/- 8.3 bpm, 11.66 +/- 1.24 mmol L( -1), and 4.1 +/- 1.0) than SPL (169.8 +/- 7.8 bpm, 13.69 +/- 0.33 mmol L(-1), and 5.8 +/- 0.6), which were lower than SPU (174.9 +/- 8.7 bpm, 15.27 +/- 0.02, mmol L(-1), and 6.3 +/- 0.5) (P < 0.05 for all analyzes). Results show that the level of eccentric muscle loading influences the pacing strategy.

Tonotopic organization of the human auditory cortex: N100 topography and multiple dipole model analysis.

The tonotopic organization of the human auditory cortex has been investigated by means of scalp potential mapping and dipole modelling of the evoked response occurring around 100 msec after the stimulus onset. The major characteristics of the topographical changes observed with increasing stimulus frequency were statistically demonstrated. Using a 3-concentric sphere head model, the scalp potential distributions can be explained in first approximation by two equivalent current dipoles, located in the supratemporal plane and mimicking the activity of both auditory cortices. To take into account the temporal aspects of the brain activities, 3 time-varying dipole strategies were tested. Frequency dependence of the dipole orientation has been evidenced in both hemispheres with the 3 models, whereas no significant change in dipole position was found. The tilt in dipole orientation could be related to the folding geometry of Heschl's gyrus, which varies with depth. In agreement with previous MEG findings, this brings new evidence for a tonotopic organization of the auditory cortical area involved in the N100 wave generation. Moreover, distinct frequency dependences of the equivalent current dipoles were observed in the early and the late parts of the N100. This study demonstrates that simple dipolar models, applied on electrical data, make it possible to reveal functionally distinct cortical areas.

Specific tonotopic organizations of different areas of the human auditory cortex revealed by simultaneous magnetic and electric recordings.

This paper presents data concerning auditory evoked responses in the middle latency range (wave Pam/Pa) and slow latency range (wave N1m/N1) recorded from 12 subjects. It is the first group study to report multi-channel data of both MEG and EEG recordings from the human auditory cortex. The experimental procedure involved potential and current density topographical brain mapping as well as magnetic and electric source analysis. Responses were compared for the following 3 stimulus frequencies: 500, 1000 and 4000 Hz. It was found that two areas of the auditory cortex showed mirrored tonotopic organization; one area, the source of N1m/N1 wave, exhibited higher frequencies at progressively deeper locations, while the second area, the source of the Pam/Pa wave, exhibited higher frequencies at progressively more superficial locations. The Pa tonotopic map was located in the primary auditory cortex anterior to the N1m/N1 mirror map. It is likely that N1m/N1 results from activation of secondary auditory areas. The location of the Pa map in A1, and its N1 mirror image in secondary auditory areas is in agreement with observations from animal studies.

Two auditory components in the 130-230 ms range disclosed by their stimulus frequency dependence.

The auditory P2 wave has been studied by means of scalp potential and scalp current density (SCD) mapping. Two components were described. One, peaking around 150 ms, probably reflects a major activity in both supra temporal planes as revealed by SCD maps (P150). The other is a bilateral temporo-parietal component peaking around 220 ms (P220). These two components were functionally disclosed by their stimulus frequency dependence. The P150 potential and SCD amplitudes significantly decrease with increasing frequencies. Whereas this could be interpreted as a modulation of the neural activity, it may also be related to a tonotopical organization of the underlying generators distinct from that previously found for the N100. No frequency effect was found on P220.