Figure 2. Peer trainers with Parkinson's disease are members of the community-based participatory research team.

The photograph shows two individuals with Parkinson's disease who participated in the first author's randomized controlled trial on high-intensity resistance (80% of a four repetition maximum was defined as high-intensity resistance training) and balance training [83]. The study took place at a public fitness facility in Tallahassee, FL, USA. Clinicians might shudder at the thought of two patients serving as peer-trainers. Indeed, at recent conferences in the USA and Europe, physiotherapist-scientists voiced understandable concerns about patient safety and ability of lay-expert trainers to deliver treatment. The photograph shows two individuals; one individual is on the foam, while the other individual is leading the balance intervention. At the time the photograph was taken, both individuals were at Hoehn and Yahr stage 2. The photograph suggests the feasibility of implementing research models that incorporate nontraditional (e.g., peer-to-peer) approaches to deliver the exercise intervention (model 2, Figure 1). The authors wish to emphasize that there are other important models of community-based exercise that are emerging in the literature that are important (for examples see Gruber [84] who uses physioptherapists as personal trainers or King and Horak [85] who employ trained exercise professionals as personal trainers [presumably model 4, Figure 1]). Reproduced with permission from [86].