What is needed is volatility coupled with price trends, which Ivarsson refers to as “directional volatility”. “What we at RPM look for is ‘directional volatility’, meaning volatility that drives markets in a certain direction”. - RPM’s executive Vice President Per Ivarsson
The depiction of trend following as a look-back straddle is based on volatility and the ability of the trend follow to capture the range. The look-back option is the potential max that a trend follower may achieve for a single trade within a time span. Nevertheless, if we think of a stochastic process for a price series, we want a mean change plus wide dispersion. It is not enough to just have volatility, the journey expressed in the volatility is critical.
Directional volatility is good short-form phrase, but it is important to understand the parts that potentially can drive trends. Trend followers want spread in price but they need paths for profit.