Soteris Xenophontos

Appetite-regulatory hormone responses on the day following a prolonged bout of moderate-intensity exercise

Exercise increases energy expenditure however acutely this does not cause compensatory changes in appetite or food intake. This unresponsiveness contrasts the rapid counter-regulatory changes seen after food restriction. The present investigation examined whether corrective changes in appetite-regulatory parameters occur after a time delay, namely, on the day after a single bout of exercise. Nine healthy males completed two, two-day trials (exercise & control) in a random order. On the exercise trial participants completed 90 min of moderate-intensity treadmill running on day one (10:30-12:00h). On day two appetite-regulatory hormones and subjective appetite perceptions were assessed frequently in response to two test meals provided at 08:00 and 12:00 h. Identical procedures occurred in the control trial except no exercise was performed on day one. Circulating levels of leptin were reduced on the day after exercise (AUC 5841 ± 3335 vs. 7266 ± 3949 ng(-1)·mL(-1)·7h, P=0.012). Conversely, no compensatory changes were seen for circulating acylated ghrelin, total PYY, insulin or appetite perceptions. Unexpectedly, levels of acylated ghrelin were reduced on the exercise trial following the second test meal on day two (AUC 279 ± 136 vs. 326 ± 136 pg(-1)·mL(-1)·3h, P=0.021). These findings indicate that short-term energy deficits induced by exercise initially prompt a compensatory response by chronic but not acute hormonal regulators of appetite and energy balance. Within this 24h time-frame however there is no conscious recognition of the perturbation to energy balance.

Test–retest reliability, validation, and “minimal detectable change” scores for frequently reported tests of objective physical function in patients with non-dialysis chronic kidney disease

ABSTRACT Physical function is an important outcome in chronic kidney disease (CKD). We aimed to establish the reliability, validity, and the “minimal detectable change” (MDC) of several common tests used in renal rehabilitation and research. In a repeated measures design, 41 patients with CKD not requiring dialysis (stage 3b to 5) were assessed at an interval of 6 weeks. The tests were the incremental shuttle walk test (ISWT), “sit-to-stand” (STS) test, estimated 1 repetition maximum for quadriceps strength (e1RM), and VO2peak by cardiopulmonary exercise testing (CPET). Reliability was assessed using intraclass correlation coefficient and Bland–Altman analysis, and absolute reliability by standard error of measurement and MDC. The ISWT, STS-60, e1RM, and CPET had “good” to “excellent” reliability (0.973, 0.927, 0.927, and 0.866), respectively. STS-5 reliability was poor (0.676). The MDC is ISWT, 20 m; STS-5, 7.5 s; STS-60, 4 reps; e1RM, 6.4 kg; VO2peak, 2.8 ml/kg/min. There was strong correlation between the ISWT and VO2peak (r = 0.73 and 0.74). While there was poor correlation between the STS-5 and e1RM (r = 0.14 and 0.47), better correlation was seen between STS-5 and ISWT (r = 0.55 and 0.74). In conclusion, the ISWT, STS-60, e1RM, and CPET are reliable tests of function in CKD. The ISWT is a valid means of exercise capacity. The MDC can help researchers and rehabilitation professionals interpret changes following an intervention.

12-weeks combined resistance and aerobic training confers greater benefits than aerobic alone in non-dialysis CKD.

There is a growing consensus that patients with chronic kidney disease (CKD) should engage in regular exercise, but there is a lack of formal guidelines. In this report, we determined whether combined aerobic and resistance exercise would elicit superior physiological gains, in particular muscular strength, compared with aerobic training alone in nondialysis CKD. Nondialysis patients with CKD stages 3b-5 were randomly allocated to aerobic exercise {AE, n = 21; 9 men; median age 63 [interquartile range (IQR) 58-71] yr; median estimated glomerular filtration rate (eGFR) 24 (IQR 20-30) ml·min-1·1.73 m-2} or combined exercise [CE, n = 20, 9 men, median age 63 (IQR 51-69) yr, median eGFR 27 (IQR 22-32) ml·min-1·1.73 m-2], preceded by a 6-wk run-in control period. Patients then underwent 12 wk of supervised AE (treadmill, rowing, or cycling exercise) or CE training (as AE plus leg extension and leg press exercise) performed three times per week. Outcome assessments of knee extensor muscle strength, quadriceps muscle volume, exercise capacity, and central hemodynamics were performed at baseline, following the 6-wk control period, and at the end of the intervention. AE and CE resulted in significant increases in knee extensor strength of 16 ± 19% (mean ± SD; P = 0.001) and 48 ± 37% ( P < 0.001), respectively, which were greater after CE ( P = 0.02). AE and CE resulted in 5 ± 7% ( P = 0.04) and 9 ± 7% ( P < 0.001) increases in quadriceps volume, respectively ( P < 0.001), which were greater after CE ( P = 0.01). Both AE and CE increased distance walked in the incremental shuttle walk test [28 ± 44 m ( P = 0.01) and 32 ± 45 m ( P = 0.01), respectively]. In nondialysis CKD, the addition of resistance exercise to aerobic exercise confers greater increases in muscle mass and strength than aerobic exercise alone.

The association of physical function and physical activity with all-cause mortality and adverse clinical outcomes in nondialysis chronic kidney disease: a systematic review

Objective: People with nondialysis-dependent chronic kidney disease (CKD) and renal transplant recipients (RTRs) have compromised physical function and reduced physical activity (PA) levels. Whilst established in healthy older adults and other chronic diseases, this association remains underexplored in CKD. We aimed to review the existing research investigating poor physical function and PA with clinical outcome in nondialysis CKD. Data sources: Electronic databases (PubMed, MEDLINE, EMBASE, Web of Science, Cochrane Central Register of Controlled Trials) were searched until December 2017 for cohort studies reporting objective or subjective measures of PA and physical function and the associations with adverse clinical outcomes and all-cause mortality in patients with nondialysis CKD stages 1–5 and RTRs. The protocol was registered on the International Prospective Register of Systematic Reviews (PROSPERO) (CRD42016039060). Review methods: Study quality was assessed using the Newcastle-Ottawa Scale and the Agency for Healthcare and Research Quality (AHRQ) standards. Results: A total of 29 studies were included; 12 reporting on physical function and 17 on PA. Only eight studies were conducted with RTRs. The majority were classified as ‘good’ according to the AHRQ standards. Although not appropriate for meta-analysis due to variance in the outcome measures reported, a coherent pattern was seen with higher mortality rates or prevalence of adverse clinical events associated with lower PA and physical function levels, irrespective of the measurement tool used. Sources of bias included incomplete description of participant flow through the study and over reliance on self-report measures. Conclusions: In nondialysis CKD, survival rates correlate with greater PA and physical function levels. Further trials are required to investigate causality and the effectiveness of physical function and PA interventions in improving outcomes. Future work should identify standard assessment protocols for PA and physical function.

Twelve weeks of supervised exercise improves self-reported symptom burden and fatigue in chronic kidney disease: a secondary analysis of the ‘ExTra CKD’ trial

Abstract Background Chronic kidney disease (CKD) patients experience a high symptom burden including fatigue, sleep difficulties, muscle weakness and pain. These symptoms reduce levels of physical function (PF) and activity, and contribute to poor health-related quality of life (HRQoL). Despite the gathering evidence of positive physiological changes following exercise in CKD, there is limited evidence on its effect on self-reported symptom burden, fatigue, HRQoL and physical activity. Methods Thirty-six patients [mean ± SD 61.6 ± 11.8 years, 22 (61%) females, estimated glomerular filtration rate: 25.5 ± 7.8 mL/min/1.73 m2] not requiring renal replacement therapy underwent 12 weeks (3 times/week) of supervised aerobic exercise (AE), or a combination (CE) of AE plus resistance training. Outcomes included self-reported symptom burden, fatigue, HRQoL and physical activity. Results Exercise reduced the total number of symptoms reported by 17% and had favourable effects on fatigue in both groups. AE reduced the frequency of ‘itching’, ‘impotence’ and ‘shortness of breath’ symptoms, and the intrusiveness for symptoms of ‘sleep disturbance’, ‘loss of muscular strength/power’, ‘muscle spasm/stiffness’ and ‘restless legs’. The addition of resistance exercise in the CE group saw a reduction in ‘loss of muscular strength/power’. No changes were seen in subjective PF or physical activity levels. AE increased self-efficacy for physical activity. Conclusions Supervised exercise had favourable effects on symptom frequency and intrusiveness, including substantial improvements in fatigue. Although the intervention did not improve self-reported physical activity levels, AE increased patients’ self-efficacy for physical activity. These favourable changes in self-reported outcomes support the important role of exercise in CKD.