the albert's paper indicates there was improvement in upper body movement, i quote it: (he sent me a copy, can't link to it).

"From a clinical perspective, our results suggest that exercise
intervention programs for PD patients can be relatively
intensive from an aerobic perspective and that patients may
need to be pushed beyond their voluntary limits to exercise at
rates sufficient to induce global improvements in motor function.
The enhanced control and coordination of upper extremity
motor activities, following a lower extremity FE intervention,
provides preliminary evidence that FE does alter central motor
control processes. One implication of improved central motor
processing is that FE is enhancing neuroplasticity or altering
brain biochemistry, both of which could alter the course
of PD.
We acknowledge that the use of an actual tandem cycle is
not feasible from a clinical perspective for a number of reasons
(eg, accessibility, requirement to have a relatively fit exercise
partner, practicality). Therefore, the next step in this line of
investigation is to determine the clinical efficacy of FE in a
larger group of PD patients using a paradigm readily and rapidly
adapted to clinical and home use. A follow-up study in
which a motor-driven stationary cycle is used for VE and FE
is currently underway. Future studies will also be directed at
identifying the duration of the motor benefits, the effects of FE
on biomechanical measures of lower extremity function and
postural stability, the optimal rate and dose of FE, and
mechanism(s) underlying the benefits of FE compared to VE.
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so it seems that the whole body benefits by aerobic exercise and the biggest bang for the buck would be using the legs.

i use a stationary bicycle and a portable stair stepper and take more sinemet as needed so i can maintain a decent aerobic rate.