EMG amplitude in maximal and submaximal exercise is dependent on signal capture rate

This study analysed the effect of different electromyographic (EMG) capture rates during maximal voluntary contraction, submaximal and maximal dynamic cycling activity on EMG amplitude and signal characteristics. Ten healthy subjects participated in this study. Peak power output (PPO) and maximal isometric force output (MVC) were measured, followed by a progressive cycle ride on a cycle ergometer. Electromyographic (EMG) data were simultaneously captured during the MVC and cycling activities at frequencies of 32, 64, 128, 256, 512, 1024 and 1984 Hz. Significant differences in amplitude were found (p < 0.01) between MVC, submaximal (SUB) and maximal cycling activities (PWATT) for all capture rates. Asymptote values for IEMG amplitude occurred at EMG capture rates of 1604 ± 235.6 Hz during MVC, 503.1 ± 236.2 Hz during PWATT and 326.2 ± 105.4 Hz during SUB cycling activity and were significantly different (p < 0.01). No significant differences were found for force/EMG ratios between PWATT and MVC at 1984 Hz capture rates (3.8 ± 1.7 N/V vs 2.5 ± 0.9 N/V) while significant differences occurred at 32 Hz capture rate (6.2 ± 3.8 vs 16.0 ± 8.0; p < 0.01). Low correlations were found between EMG activity captured at 1984 Hz during PWATT and lean thigh volume (r = 0.36) and MVC (r = 0.32). Asymptote values found on this study suggest that data captured below 326 Hz for SUB, 503 Hz for PWATT and 1604 Hz for MVC are not reliable. Therefore apparatus capturing EMG data at low frequencies from these values cannot be used for quantitative data analyses

An epidemiological study of renal pathology in tuberous sclerosis complex

Objectives: To report the frequency of renal symptoms and complications of patients with tuberous sclerosis complex (TSC), to describe the ultrasonographic appearance of the kidneys in a population-based sample, and to investigate the relationship between a history of renal haemorrhage and renal lesions identified by ultrasonography.Patients and Methods: As part of an epidemiological study, 179 patients with TSC were identified as living in the Wessex Region in the South of England. Patients were interviewed and examined in their homes, to elicit the presence of renal symptoms or a history of renal complications. Renal ultrasonography was used in consenting patients in their homes.Results: There was a history of renal complications in 16 (9%) patients; 149 consented to interview and examination, and 19 gave a history of renal symptoms in the previous year; 124 had renal ultrasonography; 86 (69%) had renal angiomyolipomas and 37 (30%) had renal cysts. Large lesions (>3 cm in diameter) were strongly associated with a history of symptomatic bleeding, although significant haemorrhage occurred in a 6-year-old child with small angiomyolipomas.Conclusions: The formation of angiomyolipoma in TSC is common. Polycystic kidney disease, renal carcinoma and renal failure, although rare, occur in TSC. Most patients with angiomyolipomas have neither complications nor symptoms. There was no appreciable difference between the sexes in the risk of developing these lesions. Although less commonly seen in the very young, there is no identifiable relationship after adolescence between age and the risk of having a renal angiomyolipoma. Bleeding tends to occur from large lesions (>3 cm) but most such patients have remained asymptomatic to date