Massimo Sacchetti

Physical exercise as therapy for type 2 diabetes mellitus

Many studies have highlighted the importance of physical activity (PA) for health, and recent evidence now points to the positive improvements associated with exercise in type 2 diabetes mellitus (T2DM). However, few physicians are willing to prescribe exercise as a therapy for diabetic patients. In addition, there is a lack of information on how to implement exercise therapy especially in long‐term exercise regimens. The purpose of this manuscript is to summarize standards of exercise therapy for patients with T2DM, both in terms of prescribing and monitoring, according to the American College of Sports Medicine and the American Diabetes Association guidelines. We present details of the exercise therapies used in long‐term studies, describing how the parameters for exercise prescription were applied in clinical practice. These parameters are described in terms of frequency, intensity, duration, mode and rate of progression in long‐term therapeutic prescriptions. Individual responses to exercise dose are discussed, and critical issues to be considered in patients with underlying disease and in T2DM patients are highlighted. Copyright

Exercising for Metabolic Control: Is Timing Important?

Atherosclerosis-related cardiovascular disease and diabetes mellitus are leading causes of mortality in the world and both disorders are closely related to the postprandial phenomena. Regular exercise is being strongly advocated as a precious tool in easing the global burden of chronic disease. Although exercise intensity, duration and frequency are well established in current guidelines for healthy and diabetic individuals, there is still no consensus on the optimal timing of exercise in relation to the last meal. The present paper reviews the existing literature on the ‘when?’ of aerobic exercise for metabolic control in healthy and diabetic individuals. Effective control of postprandial phenomena might prove to be a useful tool in the prevention of chronic disease. Exercise appears to influence glycemic and triglyceridemic responses differently depending on the meal composition and time lapse from meals. In healthy individuals, fasted-state exercise favors postprandial triglyceridemic control and the insulin sensitivity related to it. However, there is a lack of data on this matter in diabetic patients. On the other hand, when postprandial glycemia is of concern, aerobic exercise works better when performed after a meal, both in healthy and in diabetic patients.

Different effect of cadence on cycling efficiency between young and older cyclists.

PURPOSEnWe investigated the difference in the cadence-efficiency relationship between young and older competitive cyclists.nnnMETHODSnEight young (24.3 ± 5.3 yr) and eight older (65.6 ± 2.8 yr) competitive cyclists participated in two laboratory sessions. The first consisted of an incremental maximal cycling test to determine the freely chosen pedal cadence and the maximal power output at VO2max and the second for the determination of gross efficiency (GE), calculated as the ratio of external work and energy expenditure (VO2). The latter test consisted of 6-min cycling exercise bouts at 40% and 60% of maximal power output and at a cadence of 40, 60, 80, 100, and 120 rpm.nnnRESULTSnGE was lower in older cyclists than that in young cyclists at all cadences considered and at both levels of power output (P < 0.01). Peak efficiency was reached at 60 rpm in young cyclists (21.2% ± 1.9%), whereas in older cyclists this was observed already at 40 rpm and was not different from that at 60 rpm (18.3% ± 0.6%). The decline in GE with the increase in cadence was more pronounced in older than in young cyclists (P < 0.01) and was mitigated by the increase in power output more in the latter than in the former. These observations were in line with a lower freely chosen cadence recorded during the maximal test in older than that in young (P < 0.01).nnnCONCLUSIONSnThe present data indicate that the effect of cadence on cycling efficiency is different between young and older cyclists and that it seems more disadvantageous for the latter to use high cadences. This may help explain why our older cyclists chose to pedal at lower cadences than the younger.

Neuromuscular Dysfunction in Diabetes: Role of Nerve Impairment and Training Status.

PURPOSEnThe purpose of this study was to investigate the effect of diabetes, motor nerve impairment, and training status on neuromuscular function by concurrent assessment of the torque-velocity relationship and muscle fiber conduction velocity (MFCV).nnnMETHODSnFour groups were studied (n = 12 each): sedentary patients with diabetes in the first (lower) and fourth (higher) quartile of motor nerve conduction velocity (D1 and D4, respectively), trained diabetic (TD) patients, and nondiabetic sedentary control (C) subjects. Maximal isometric and isokinetic contractions were assessed over a wide range of angular velocities for the elbow flexors and knee extensors to evaluate the torque-velocity relationship. Simultaneously, MFCV was estimated from surface electromyography of the vastus lateralis and biceps brachii.nnnRESULTSnIsometric strength was similar among groups. The dynamic strength of elbow flexors was reduced in patients with diabetes at the higher contraction speeds. The strength of knee extensors was lower in sedentary patients with diabetes at all velocities considered, with significantly lower values in D1 than that in D4 at 60°, 90°, and 120°·s(-1), whereas it was similar between TD and C subjects, especially at low contraction velocities. At the vastus lateralis, but not the biceps brachii, MFCV was lower in D1 and D4 as compared with TD and C subjects, showing similar values.nnnCONCLUSIONSnMuscle weakness in diabetes affects also the upper limb, although to a lower extent than the lower limb, is only partly related to motor nerve impairment, and is dependent on contraction velocity. Exercise training might counteract diabetes-induced alterations in muscle fiber contractile properties and MFCV.

Correlates of muscle strength in diabetes The study on the assessment of determinants of muscle and bone strength abnormalities in diabetes (SAMBA)

BACKGROUND AND AIMSnApart from late motor nerve dysfunction, factors affecting muscle strength in diabetes are largely unknown. This study was aimed at assessing muscle strength correlates in diabetic subjects encompassing a wide range of peripheral nerve function and various degrees of micro and macrovascular complications.nnnMETHODS AND RESULTSnFour-hundred consecutive patients with type 1 and 2 diabetes (aged 46.4 ± 13.9 and 65.8 ± 10.3 years, respectively) from the Study on the Assessment of Determinants of Muscle and Bone Strength Abnormalities in Diabetes (SAMBA) were examined for upper and lower body muscle isometric maximal voluntary contraction by dynamometry. Univariate and multivariate regression analyses were applied to identify strength correlates. Isometric force at both the upper and lower limbs was significantly lower in subjects with than in those without any complication. At univariate analysis, it was strongly associated with age, diabetes duration, physical activity (PA) level, cardio-respiratory fitness, anthropometric parameters, surrogate measures of complications, and parameters of sensory and autonomic, but not motor (except amplitude) neuropathy. Multivariate analysis revealed that upper and lower body strength correlated independently with male gender and, inversely, with age, autonomic neuropathy score (or individual autonomic function abnormalities), and vibration perception threshold, but not sensory-motor neuropathy score. Diabetes duration and PA level were excluded from the model.nnnCONCLUSIONSnBoth upper and lower body muscle strength correlate with measures of diabetic complications and particularly with parameters of sensory and especially autonomic nerve function, independently of diabetes duration and PA level, thus suggesting the involvement of mechanisms other than manifest motor nerve impairment.

Respiratory frequency is strongly associated with perceived exertion during time trials of different duration

ABSTRACT In order to provide further insight into the link between respiratory frequency (fR) and the rating of perceived exertion (RPE), the present study investigated the effect of exercise duration on perceptual and physiological responses during self-paced exercise. Nine well-trained competitive male cyclists (23 ± 3 years) performed a preliminary incremental ramp test and three randomised self-paced time trials (TTs) differing in exercise duration (10, 20 and 30 min). Both RPE and fR increased almost linearly over time, with a less-pronounced rate of increase when absolute exercise duration increased. However, when values were expressed against relative exercise duration, no between-trial differences were found in either RPE or fR. Conversely, between-trial differences were observed for minute ventilation (E), O2 and heart rate (HR), when values were expressed against relative exercise duration. Unlike the relationship between RPE and both E and HR, the relationship between RPE and fR was not affected by exercise duration. In conclusion, fR, but not E, HR or O2, shows a strong relationship to RPE and a similar time course, irrespective of exercise duration. These findings indicate that fR is the best correlate of RPE during self-paced exercise, at least among the parameters and for the range of durations herein investigated.

Non-invasive assessment of muscle fiber conduction velocity during an incremental maximal cycling test

Muscle fiber conduction velocity (MFCV) gives critical information on neuromuscular control and can be considered a size principle parameter, being suggestive of motor unit recruitment strategies. MFCV has been recently measured during constant-load sub-maximal cycling exercise and was found to correlate positively with percentage of type I myosin heavy chain. The aim of this study was to test the hypothesis that MFCV measured during an incremental cycling test using surface electromyography (sEMG), can be sensitive to the different metabolic requests elicited by the exercise. In particular, the relationship between ventilatory threshold (T-vent), V()O(2max) and MFCV was explored. Eleven male physically active subjects (age 30+/-9 years) undertook a 1-min incremental cycling test to exhaustion. T-vent and V()O(2max) were measured using an open circuit breath by breath gas analyzer. The sEMG was recorded from the vastus lateralis muscle with an adhesive 4-electrodes array, and the MFCV was computed on each sEMG burst over the last 30-s of each step. The mean V()O(2max) obtained during the maximal test was 53.32+/-2.33 ml kg(-1) min(-1), and the T-vent was reached at 80.77+/-3.49% of V()O(2max). In all subjects reliable measures of MFCV were obtained at every exercise intensity (cross correlation values >0.8). MFCV increased linearly with the mechanical load, reaching a maximum value of 4.28+/-0.67 ms(-1) at an intensity corresponding to the T-vent. Thereafter, MFCV declined until maximal work intensities. This study demonstrates that MFCV can be used as non-invasive tool to infer MUs recruitment/derecruitment strategies even during dynamic exercise from low to maximal intensities.

Muscle fibre conduction velocity and cardiorespiratory response during incremental cycling exercise in young and older individuals with different training status

We investigated the effect of ageing and training on muscle fibre conduction velocity (MFCV) and cardiorespiratory response during incremental cycling exercise. Eight young (YT; 24+/-5 yrs) and eight older (OT; 64+/-3 yrs) cyclists, together with eight young (YU; 27+/-4 yrs) and eight older (OU; 63+/-2 yrs) untrained individuals underwent to an incremental maximal test on a cycle ergometer. Ventilatory threshold (VT), respiratory compensation point (RCP) and maximal oxygen uptake (VO(2)max) were identified and MFCV recorded from the vastus lateralis muscle using surface electromyography with linear arrays electrodes. In YT MFCV increased with the exercise intensity, reaching a peak of 4.99+/-1.02 [m/s] at VT. Thereafter, and up to VO(2)max, MFCV declined. In YU MFCV showed a similar trend although the peak [4.55+/-0.53m/s] was observed, at 75% of VO(2)max an intensity higher than VT (66% of VO(2)max). In both YT and YU MFCV did not decline until RPC, which occurred at 78% VO(2)max in YU and at 92% VO(2)max (P<0.01) in YT. Differently from young individuals, MFCV in older subjects did not increase with exercise intensity. Moreover, maximal MFCV in OU was significantly lower [3.53+/-0.40 m/s;] than that of YT (P<0.005) and YU (P<0.05). The present study shows that, especially in young individuals, MFCV reflects cardiorespiratory response during incremental dynamic cyclic exercise and hence can be used to investigate motor unit recruitment strategies.

Neuromuscular dysfunction in type 2 diabetes: underlying mechanisms and effect of resistance training

Diabetic patients are at higher risk of developing physical disabilities than non‐diabetic subjects. Physical disability appears to be related, at least in part, to muscle dysfunction. Several studies have reported reduced muscle strength and power under dynamic and static conditions in both the upper and lower limbs of patients with type 2 diabetes. Additional effects of diabetes include a reduction in muscle mass, quality, endurance and an alteration in muscle fibre composition, though the available data on these parameters are conflicting. The impact of diabetes on neuromuscular function has been related to the co‐existence of long‐term complications. Peripheral neuropathy has been shown to affect muscle by impairing motor nerve conduction. Also, vascular complications may contribute to the decline in muscle strength. However, muscle dysfunction occurs early in the course of diabetes and affects also the upper limbs, thus suggesting that it may develop independently of micro and macrovascular disease. A growing body of evidence indicates that hyperglycaemia may cause an alteration of the intrinsic properties of the muscle to generate force, via several mechanisms. Recently, resistance exercise has been shown to be an effective strategy to counteract the deterioration of muscular performance. High‐intensity exercise seems to provide greater benefits than moderate‐intensity training, whereas the effect of a power training is yet unknown. This article reviews the available literature on the impairment of muscle function induced by diabetes, the underlying mechanisms, and the effect of resistance training on this defect. Copyright

Cardio-respiratory and electromyographic responses to ergometer and on-water rowing in elite rowers.

The aim of this study was to compare muscle activation and cardio-respiratory response during ergometer and on-water rowing. Nine internationally competitive rowers (five Olympic Games medal winners, age 25.6xa0±xa04.8xa0years) were requested to perform a 1,000xa0m race simulation test in the two conditions. Surface electromyographic (sEMG) signals from trapezius superior (TRS), latissimus dorsi (LD), biceps brachii (BB), rectus femoris (RF), vastus medialis (VAM), vastus lateralis (VAL), biceps femoris (BF) and tibialis anterior (TA) muscles were recorded continuously during the tests together with other cardio-respiratory parameters: heart rate (HR), ventilation (VE), oxygen consumption