Extreme pace unsettles most batsmen and many get just as twitchy against probing slow bowlers whose weapons are flight and guile.
The Ashes series has painted those issues in bright colours for England after heavy successive losses against the pace of Mitchell Starc, Josh Hazlewood, Pat Cummins and the off-spinning craft of Nathan Lyon.
Relentless inquiries from that group have gnawed at the technique of England's batsmen and eaten into their belief as their judgment and footwork has betrayed that anxiety. Prodding strokes and hesitant movements on unfamiliar pitches is no recipe for success against such a concentrated attack.
Alastair Cook and Joe Root have developed strong records in the top-order against most sides but have been unable to find that flow against an Aussie attack which has all the experience to exploit their home conditions and offers no let-up.
Serious pace from both ends with troubling bounce and movement off the track or the mix of speed from one end and spin from Lyon at the other with his drift, spin, change of pace and attacking fields has been too potent for the Poms.