A recent study concluded that stretching the Achilles tendon and plantar fascia simultaneously can reduce pain associated with plantar fasciitis more so than just stretching the Achilles tendon alone.
The results of the study showed that patients’ pain went away faster while stretching the Achilles tendon and plantar fascia at the same time vs the group only stretching the Achilles Tendon.
Is this the best way to stretch? Although, I believe this to be the best way to stretch for plantar fasciitis, many studies on foot pain elimination are not flawless. Many studies do not have control groups or they consist of poor group choices where the subjects being compared are not exactly alike. For example, the size, weight and biomechanical function of the subjects may vary (among other things). This explains why when you read what to do for your plantar fasciitis, you will, sometimes get contradictory suggestions.
Although a tight Achilles tendon is often associated with plantar fasciitis, I believe that this “Double” type of stretching helps squeeze the inflammation (fluid) buildup out of the painful area rather than simply stretching the fascia. So “stretching” the Achilles tendon and plantar fascia is like “walking it off” after a period of rest. As I have repeatedly questioned, how is the fascia stretching? It is not attached to any muscles but rather is attached to the heel bone (with some fibers wrapping around to the Achilles tendon) and attached distally to the soft tissue about the toes. When it is stretched (I believe it is not stretching as it is a very thick fibrous (leathery) band of tissue) it is really compressing the area between the fascia and underside of the heel bone that fills up with inflammatory fluid.
Therefore, I believe this type of stretching is helpful but more so with doing it along with massaging compression of the area of pain which moves the excess fluid (inflammation) out of the area.
 Effectiveness of the Simultaneous Stretching of the Achilles Tendon and Plantar Fascia in Individuals With Plantar Fasciitis
Phoomchai Engkananuwat, PT, BSc, Rotsalai Kanlayanaphotporn, PT, PhD, Nithima Purepong, PT, PhD First Foot & Ankle International October 6, 2017