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BACKGROUND: Diagnosing anal incontinence (AI) based on manometry results is challenging due to the variation of the normal values and overlap between patients with and without AI. This study aimed to perform a systematic review on the difference in sphincter fatigability between patients with and without AI. METHODS: MEDLINE, EMBASE, SCOPUS, and Google Scholar were searched. Studies were included if they included adult patients and assessed anal sphincter fatigability between using manometry. The effect size was estimated as the standardized mean difference (SMD) with 95% confidence intervals. A random-effects model was used. RESULTS: The database searches identified 125 unique articles, and five additional articles were identified from the reference list of articles. One hundred thirteen were excluded through title and abstract review. Nine articles were included in the final analysis. There was no statistically significant difference in the resting pressure between the two groups. Patients with AI had significantly lower squeeze pressure. There was no statistically significant difference between the groups in the fatigue rate. The FRI was significantly lower in patients with AI (SMD 1.636, p = 0.001). Approximately a third of the patients in one study were able to maintain a contraction for 20s without reducing pressure. There was significant heterogeneity in the studies. The data available were inadequate for more robust calculations. CONCLUSIONS: Sphincter fatigability, measured by the Fatigability Rate Index, has good discriminating power for anal incontinence. A standardized protocol needs to be followed by future researchers. Graphical Abstract The analysis used six studies with 413 patients to compare Fatigue Rate Index between patients with AI and controls. All studies reported a lower FRI in patients with incontinence and the FRI was significantly lower in patients with AI (standardized mean difference [SMD] 1.636, p= 0.001). Conflicting results were reported on the correlation between FRI and AI symptom scores.

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Background: Recent EEG-SSVEP signal based BCI studies have used high frequency square pulse visual stimuli to reduce subjective fatigue. However, the effect of total harmonic distortion (THD) has not been considered. Compared to CRT and LCD monitors, LED screen displays high-frequency wave with better refresh rate. In this study, we present high frequency sine wave simple and rhythmic patterns with low THD rate by LED to analyze SSVEP responses and evaluate subjective fatigue in normal subjects. Materials and Methods: We used patterns of 3-sequence high-frequency sine waves (25, 30, and 35 Hz) to design our visual stimuli. Nine stimuli patterns, 3 simple (repetition of each of above 3 frequencies e.g., P25-25-25) and 6 rhythmic (all of the frequencies in 6 different sequences e.g., P25-30-35) were chosen. A hardware setup with low THD rate (<0.1%) was designed to present these patterns on LED. Twenty two normal subjects (aged 23-30 (25 ± 2.1) yrs) were enrolled. Visual analog scale (VAS) was used for subjective fatigue evaluation after presentation of each stimulus pattern. PSD, CCA, and LASSO methods were employed to analyze SSVEP responses. The data including SSVEP features and fatigue rate for different visual stimuli patterns were statistically evaluated. Results: All 9 visual stimuli patterns elicited SSVEP responses. Overall, obtained accuracy rates were 88.35% for PSD and > 90% for CCA and LASSO (for TWs > 1 s). High frequency rhythmic patterns group with low THD rate showed higher accuracy rate (99.24%) than simple patterns group (98.48%). Repeated measure ANOVA showed significant difference between rhythmic pattern features (P < 0.0005). Overall, there was no significant difference between the VAS of rhythmic [3.85 ± 2.13] compared to the simple patterns group [3.96 ± 2.21], (P = 0.63). Rhythmic group had lower within group VAS variation (min = P25-30-35 [2.90 ± 2.45], max = P35-25-30 [4.81 ± 2.65]) as well as least individual pattern VAS (P25-30-35). Discussion and Conclusion: Overall, rhythmic and simple pattern groups had higher and similar accuracy rates. Rhythmic stimuli patterns showed insignificantly lower fatigue rate than simple patterns. We conclude that both rhythmic and simple visual high frequency sine wave stimuli require further research for human subject SSVEP-BCI studies.

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INTRODUCTION: Some of the physiological factors and athletic performance might show variation along the phases of menstrual cycle. The alterations seen in these physiological parameters of various systems relating to oscillations in hormonal levels do affect the autonomic nervous system and metabolic functions. Former studies heave inconclusively about the influence of hormones on exercise performance, predominantly muscle strength and rate of fatigue during different phases of the menstrual cycle. Studies regarding influence of these variations during bleeding phase were not done. AIM: To evaluate the muscle strength variations and also the rate of fatigue during various phases of the menstrual cycle in young adults. MATERIALS AND METHODS: This was a prospective study conducted among 100 healthy adult female volunteers aged 18-24 years, with normal regular menstrual cycles persistent between 26- 32 days (average of 28 days), for a minimum of last 6 months. Muscle strength was assessed by calculating the work done and fatigue rate using Mosso's ergograph and by handgrip dynamometer strength. Each subject was evaluated consecutively for two menstrual cycles in all three phases which were classified as Phase 1- Menstrual phase, Phase 2- Follicular phase and Phase 3- Luteal phase. The data obtained was analysed by statistical tool One-way ANOVA followed by a post-hoc Tukeys test. A p-value of ≤ 0.05 was considered significant. RESULTS: The amount of work done and handgrip strength was significantly higher in phase 2 (p<0.001) and relatively reduced in phase 1 and 3 (p<0.001) of menstrual cycle. In terms of fatigue rate percentage, phase 2 showed significantly lesser values (p<0.001) as compared to phase 1 and 3 of menstrual cycle. CONCLUSION: We conclude that the cyclical variation in endogenous reproductive hormones increases the muscle strength in follicular phase of the menstrual cycle. Thus provide support for the influence of these hormones in regulation of these parameters in the premenopausal age group.

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Literature has not shown the minimum time required to recover from muscle fatigue after a prolonged trunk isometric contraction. The purpose of this study was to determine if the lumbar multifidus (LM) and gluteus maximus (GM) muscles would recover from fatigue after three different rest periods following performance of a back extension endurance test. Endurance time and electromyographic (EMG) activity of bilateral LM and GM muscles were collected from 12 healthy adults during a modified Biering-Sørensen test. On three separate visits, each participant performed two modified Biering-Sørensen tests, one before and one after a rest period (3, 6 or 9 min). For each endurance test, endurance time was measured and both mean and median EMG frequency fatigue rates were calculated. The results showed a significantly reduced endurance time and normalized mean frequency fatigue rates on the second modified Biering-Sørensen endurance test regardless of the rest periods (3, 6, and 9 min). This suggests that adequate rest should be considered for fatigue recovery when designing a back and hip endurance exercise program, and that future studies should investigate a rest time longer than 9 minutes for fatigue recovery following a modified Biering-Sørensen endurance test.

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PURPOSE: The fatigue rate index (FRI) has been developed to access sustained voluntary contraction of the external anal sphincter. This study is designed to refine the technical aspects of measuring the FRI and to re-evaluate its clinical significance. METHODS: Thirty-eight patients with fecal incontinence (19 males, 19 females) and 37 (21 males, 16 females) controls were studied. Anal manometry was performed by using standard protocols. Fatigue was measured over a 20-sec squeeze at a high-pressure zone. The FRI was calculated from the maximum squeeze pressure (MXSP) and the fatigue rate. For the accuracy of the calculation, the mean resting pressure (MRP) was calibrated to zero before the metric procedure, representative segments of the calculation were selectively designated as those denoting sustained squeeze, and representative channels were designated from among 8 channels by using 3 or more of those showing typical sustaining-pressure curves. RESULTS: No difference in demographic factors was detected between the two groups. Basic manometric parameters were significantly different between the two groups (MRP, 29.4+/-21.3 vs. 44.4+/-17.8 mmHg, P=0.0015; MXSP, 205.9+/-98.0 vs. 274.2+/-106.5 mmHg, P=0.0051). The FRI was also significantly different (29.8+/-14.3 vs. 86.3+/-127.1 sec, P=0.0108). The areas under the receptor operating-characteristic curves for the MRP, the MXSP, and the FRI were 0.72, 0.69, and 0.84, respectively. The sensitivity and the specificity of the FRI for detecting fecal incontinence were 80% and 65% at 40 sec as a cut-off point. CONCLUSION: The FRI was proven to be more accurate than the MRP and the MXSP in detecting incontinence. With adequate modifications of the measuring method, measurement of the FRI could be done more easily and conveniently, but its cut-off point for detecting fecal incontinence was lower than previously reported.

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PURPOSE: Fatigue rate index (FRI) is one of relatively unknown parameters of anal manometry. It was devised to assess sustained voluntary contractibility of external anal sphincter muscle. We designed this study to determine the predictability of FRI in evaluating patients with symptoms of fecal incontinence. METHODS: Consecutive male patients with fecal incontinence, those with prolapsed hemorrhoids but without any kind of incontinence symptom, and male healthy volunteers who have no anal symptom were grouped as A, B, C. Anal manometric parameters including FRI were measured and compared statistically among them. RESULTS: All subjects were 84. Group A 27, Group B 33, and Group C 24. Their ages were 33.33+/-2.91 (mean SE), 39.27+/-2.80, and 50.81+/-4.33, respectively. Mean resting pressures (mmHg) were 78.11 6.56 for group A, 81.18+/-7.19 for group B, and 57.81+/-7.80 for group C. Maximum resting pressures (mmHg) were 98.67+/-9.69, 100.82+/-8.49, 78.13+/-10.26. Mean squeeze pressures (mmHg) were 229.11+/-18.72, 248.18+/-23.03, 156.94+/-17.89. Maximum squeeze pressures (mmHg) were 286.50+/-33.76, 298.59+/-27.83, 187.38+/-21.08. Resting radial asymmetries (%) were 18.85+/-2.81, 19.85+/-2.31, 28.70+/-4.79. Squeeze radial asymmetries were 15.73+/-2.90, 16.29+/-1.96, 16.47+/-2.95. Fatigue rates were 0.90+/-0.21, 1.17+/-0.15, 1.38+/-0.40. Fatigue rate indices (min.) were 3.76+/-0.41, 2.63+/-0.20, 1.94+/-0.26, respectively. Differences between group A and group C were statistically significant in mean squeeze pressure (P=0.0093), maximum squeeze pressure (P= 0.0190) and FRI (P=0.0008). Those between group B and group C were significant also in mean squeeze pressure (P=0.005), maximum squeeze pressure (P=0.0051), and FRI (P=0.0396). Multiple logistic regression analysis revealed that independently significant parameters were age (P= 0.002) and FRI (P=0.007). Cut-off point of FRI for incontinence with maximum sensitivity and specificity was 2.4min. by ROC (receiver operating characteristics) analysis. CONCLUSION: FRI is a meaningful parameter in predicting fecal incontinence, which can be used in assessment of sphincter function and future treatment protocols.

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