To Styex's point I will say this. The bigger the timeframe one uses to monitor regressions to the mean the better the performance of a martingale EA when reversing.

For instance if you put a 5EMA based on the high and the low on a 4 hour chart, you will notice as price runs up quickly and the candles (I prefer these over bars) are long, you will notice that a gap forms between the two moving averages as price continues to rise or fall.

When using other indicators such as RSI, CCI or even Stochastics you can to a reasonable degree find when the regression will occur (change settings of oscillators to suit your needs). The more the gap lasts due to the force of the move the better the retracement.

Typically the gap between the moving average and the opening price that forms when the new candle opens provides the best clue to mean regression.