The derivation of this idea starts with the noted sociologist and social movement expert Neil Smelser, who theorized that social movements (and Smelser was really talking about Movements with a capital M, the kind that involve freedom, justice, fairness and the like) come about because of a combination of factors starting with social strain.

FORBES: Restlessness Fuels Marketing Movements

Toure feels Barcelona are starting to feel the strain of playing fast-paced football with trying to clinch a third European Cup, win the Spanish league and the Spanish Cup (Copa del Rey).

BBC: Toure fears Barcelona tiredness

For the Bobcats, Josh McRoberts (left shoulder strain) was out, replaced in the starting lineup by Byron Mullens.

NPR: Wade Out With Right Knee Soreness

The President had the opportunity to talk to leaders in the region, including King Abdullah, who talked about the significant humanitarian strain that is being felt by the Syrian people and is starting to have an impact on other countries in the region.

WHITEHOUSE: Press Briefing by Deputy Press Secretary Josh Earnest