Reply: To Exercise at High Intensity Heart Rate or Not to Exercise at High Intensity Heart Rate?

We have read the reply to our letter1 with interest, and we welcome the opportunity to further clarify our position on the role of exercise in patients with Parkinson's disease (PD). The primary reason for writing our letter was to caution against excessive exercise undertaken with the aim of reversing the Parkinson's disease process, rather than to question the value of high-intensity training. The point to which the authors (Corcos et al.) objected was our remark: “If exercise does indeed have a positive effect on the nigrostriatal system, moderate exercise might be sufficient.”2 The authors refer to the positive clinical effects—specifically improvements in UPDRS-III scores—of high-intensity exercise, as demonstrated by several studies.3, 4 We believe it is important to distinguish such clinical benefits from a disease-modifying effect, the latter of which has not been demonstrated in these studies. Our remark pertained to the possibility of a disease-modifying effect of moderate- or high-intensity exercise (“reversing an abnormal DAT-scan or the disease”), which would require a different study design to establish, such as quantifying the number of dopaminergic neurons2 or using DAT-SPECT imaging.5 However, we agree with the authors that, in the context of our main message, it is important to emphasize the evidence for the clinical benefit of high-intensity exercise. Therefore, the response to our letter by Corcos et al. provides an important addition to our message. (1) Research project: not applicable; (2) Statistical analysis: not applicable; (3) Manuscript: A. Writing of the first draft B. Review and critique. L.I.B.: 3A, 3B A.B.: 3B K.P.B.: 3A, 3B Ethical Compliance Statement: Ethical guidelines are not applicable. Patient consent was not necessary for this work. We confirm that we have read the Journal's position on issues involved in ethical publication and affirm that this work is consistent with those guidelines. Funding Sources and Conflict of Interest: No specific funding was received for this work. The authors declare that there are no conflicts of interest relevant to this work. Financial Disclosure for the Last 12 Months: L.I.B. has no additional disclosures to report. A.B. has been funded by MRC-NIHR, MSA Trust, and Land UCL Centre for Equality Research in Brain Sciences. K.P.B. has been funded by Parkinson's UK, Edmund J. Safra Foundation, ESPR, American PD association, and NIHR UCLH BRC.