Perceived exertion and muscle efficiency in Parkinson's disease: L-DOPA effects

Evidence that Neuromuscular Fatigue Is not a Dogma in Patients with Parkinson's Disease

PURPOSE

Given the increased level of fatigue frequently reported by patients with Parkinson's disease (PD), this study investigated the interaction between central and peripheral components of neuromuscular fatigue (NF) in this population compared with healthy peers.

METHODS

Changes in maximal voluntary activation (ΔVA, central fatigue) and potentiated twitch force (ΔQtw,pot, peripheral fatigue) pre-post exercise were determined via the interpolated twitch technique in 10 patients with PD and 10 healthy controls (CTRL) matched for age, sex, and physical activity. Pulmonary gas exchange, femoral blood flow, and quadriceps EMG were measured during a fatiguing exercise (85% of peak power output [PPO]). For a specific comparison, on another day, CTRL repeat the fatiguing test matching the time to failure (TTF) and PPO of PD.

RESULTS

At 85% of PPO (PD, 21 ± 7 W; CTRL, 37 ± 22 W), both groups have similar TTF (~5.9 min), pulmonary gas exchange, femoral blood flow, and EMG. After this exercise, the maximal voluntary contraction (MVC) force and Qtwpot decreased equally in both groups (-16%, P = 0.483; -43%, P = 0.932), whereas VA decreased in PD compared with CTRL (-3.8% vs -1.1%, P = 0.040). At the same PPO and TTF of PD (21 W; 5.4 min), CTRL showed a constant drop in MVC, and Qtwpot (-14%, P = 0.854; -39%, P = 0.540), instead VA decreased more in PD than in CTRL (-3.8% vs -0.7%, P = 0.028).

CONCLUSIONS

In PD, central NF seems exacerbated by the fatiguing task which, however, does not alter peripheral fatigue. This, besides the TTF like CTRL, suggests that physical activity may limit NF and counterbalance PD-induced degeneration through peripheral adaptations.

An Acute Application of Cerebellar Transcranial Direct Current Stimulation Does Not Improve Motor Performance in Parkinson's Disease

Transcranial direct current stimulation of the cerebellum (c-tDCS) improves motor performance in young and old adults. Based on the cerebellar involvement in Parkinson’s disease (PD), c-tDCS could have potential to improve motor function in PD. The purpose was to determine the effects of c-tDCS on motor performance in PD while participants were on medications. The study was a randomized, double-blind, SHAM-controlled, between-subjects design. Twenty-two participants with PD were allocated to either a c-tDCS group or a SHAM group. All participants completed one experimental session and performed two motor tasks with their most affected hand in a Baseline condition (no stimulation) and an Experimental condition. The motor tasks were a visuomotor isometric precision grip task (PGT) and a rapid arm movement task (AMT). The primary dependent variables were force error and endpoint error in the PGT and AMT, respectively. There were no significant differences in force error or endpoint error in the Experimental condition between the c-tDCS and SHAM groups. These results indicate that an acute application of c-tDCS does not enhance motor performance in hand and arm tasks in PD. Longer-term c-tDCS application over multiple days may be needed to enhance motor function in PD.

Exercise as medicine - evidence for prescribing exercise as therapy in 26 different chronic diseases

This review provides the reader with the up-to-date evidence-based basis for prescribing exercise as medicine in the treatment of 26 different diseases: psychiatric diseases (depression, anxiety, stress, schizophrenia); neurological diseases (dementia, Parkinson's disease, multiple sclerosis); metabolic diseases (obesity, hyperlipidemia, metabolic syndrome, polycystic ovarian syndrome, type 2 diabetes, type 1 diabetes); cardiovascular diseases (hypertension, coronary heart disease, heart failure, cerebral apoplexy, and claudication intermittent); pulmonary diseases (chronic obstructive pulmonary disease, asthma, cystic fibrosis); musculo-skeletal disorders (osteoarthritis, osteoporosis, back pain, rheumatoid arthritis); and cancer. The effect of exercise therapy on disease pathogenesis and symptoms are given and the possible mechanisms of action are discussed. We have interpreted the scientific literature and for each disease, we provide the reader with our best advice regarding the optimal type and dose for prescription of exercise.

Speech-related fatigue and fatigability in Parkinson's disease

This study tested the assumption that speech is more susceptible to fatigue than normal in persons with dysarthria. After 1 h of speech-like exercises, participants with Parkinson's disease (PD) were expected to report increased perceptions of fatigue and demonstrate fatigability by producing less precise speech with corresponding acoustic changes compared to neurologically normal participants. Twelve adults with idiopathic PD and 13 neurologically normal adults produced sentences with multiple lingual targets before and after six 10-min blocks of fast syllable or word productions. Both groups reported increasing self-perceived fatigue over time, but trained listeners failed to detect systematic differences in articulatory precision or speech naturalness between sentences produced before and after speech-related exercises. Similarly, few systematic acoustic differences occurred. These findings do not support the hypothesis that dysarthric speakers are particularly susceptible to speech-related fatigue; instead, speech articulation generally appears to be resistant to fatigue induced by an hour of moderate functional exercises.

Exercise alleviates Parkinsonism: clinical and laboratory evidence

The present review examines the putative benefits for individuals afflicted with Parkinsonism, whether in the clinical setting or in the animal laboratory, accruing from different exercise regimes. The tendency for patients with Parkinson's disease (PD) to express either normal or reduced exercise capacity appears regulated by factors such as fatigue, quality-of-life and disorder severity. The associations between physical exercise and risk for PD, the effects of exercise on idiopathic Parkinsonism and quality-of-life, the effects of exercise on animal laboratory models of Parkinsonism and dopamine (DA) loss following neurotoxic insults, and the effects of exercise on the DA precursor, L-Dopa, efficacy are examined. It would appear to be case that in view of the particular responsiveness of the dopaminergic neurons to exercise, the principle of 'use it or lose' may be of special applicability among PD patients.

Perceptions of effort during handgrip and tongue elevation in Parkinson's disease

BACKGROUND

Fatigue and the accompanying perception of effort are often heightened in Parkinson's disease.

OBJECTIVES

To compare performance on three sense-of-effort tasks between patients with PD and matched neurologically normal control subjects.

METHODS

Sixteen PD subjects and 16 normal subjects performed three tasks to assess sense of effort: self-ratings of effort using direct-magnitude estimation, generating pressures at various levels of effort, and sustaining a submaximal level of effort. The latter two tasks were done with handgrip and tongue elevation.

RESULTS

Two of the three tasks successfully differentiated the groups. Subjects with PD provided significantly higher ratings of effort for general daily activities and for speech. During the constant-effort task, pressure curves decayed more rapidly for the PD subjects.

CONCLUSIONS

Performance by PD subjects on the constant-effort task resembled that by normal adults who were pre-fatigued in previous experiments. Results support greater than normal sense-of-effort related to fatigue in PD, and provide preliminary validation of a performance-based physiologic task to assess abnormal sense of effort in this population.

The effect of COMT inhibition with entacapone on cardiorespiratory responses to exercise in patients with Parkinson's disease

The inhibition of catechol-O-methyltransferase (COMT) may impair catecholamine clearance resulting in unwanted cardiac and hemodynamic events. We therefore studied the effects of entacapone, an inhibitor of peripheral COMT, on cardiorespiratory and plasma noradrenaline (NA) responses to exercise and on respiratory muscle strength in l-dopa treated patients with Parkinson's disease (PD). A randomized, double-blind, cross-over study with two 1week treatment periods was performed in 15 PD patients. The test battery included analysis of hemodynamics, gas exchange parameters and plasma NA during a maximal exercise test, assessment of maximal static airway pressures and pre- and post-exercise motor scores of the Unified Parkinson's Disease Rating Scale (UPDRS). The first test was done after withholding l-dopa overnight ('run-in' test, off-phase). The second and third tests were done in on-phase after 1week treatment with either entacapone 200mg or placebo given with each dose of l-dopa. No differences in maximal work load, plasma NA, or in cardiorespiratory responses to either maximal or work rate standardized submaximal exercise were observed between entacapone and placebo, except for O(2) pulse, which was slightly lower (p < 0.05) after entacapone at submaximal exercise level. Maximal airway pressures were similar between the study treatments and run-in. Exercise had no effect on motor UPDRS after either study treatment or during the run-in test. No serious adverse events were observed. The results of this study suggest that entacapone does not change the work capacity, work efficiency or respiratory muscle strength in l-dopa treated PD patients with mild to moderate disease severity, and that its use with l-dopa seems to be safe in conditions of maximal physical effort. However, data from the long-term use of COMT inhibitors are needed to confirm these findings.