This builds speed and endurance if you do it right.
Use a metronome and slowly turn the tempo up.  IT WORKS!

4/4 S|O-O-O-O-O-O-O-O-|OOOOOOOOOOOOOOOO|  X8
     |1 + 2 + 3 + 4 + |1e+a2e+a3e+a4e+a|
      L L L L L L L L  LRLRLRLRLRLRLRLR
      R R R R R R R R  RLRLRLRLRLRLRLRL


7/8 S|O-O-O-O-O-O-O-|OOOOOOOOOOOOOO|  X8
     |1 2 3 4 5 6 7 |1+2+3+4+5+6+7+|
      L L L L L L L  LRLRLRLRLRLRLR
      R R R R R R R  RLRLRLRLRLRLRL

3/4 S|O-O-O-O-O-O-|OOOOOOOOOOOO|  X8
     |1 + 2 + 3 + |1e+a2e+a3e+a|
      L L L L L L  LRLRLRLRLRLR
      R R R R R R  RLRLRLRLRLRL

5/8 S|O-O-O-O-O-|OOOOOOOOOO|  X8
     |1 2 3 4 5 |1+2+3+4+5+|
      L L L L L  LRLRLRLRLR
      R R R R R  RLRLRLRLRL

2/4 S|O-O-O-O-|OOOOOOOO|  X8
     |1 + 2 + |1e+a2e+a|
      L L L L  LRLRLRLR
      R R R R  RLRLRLRL

3/8 S|O-O-O-|OOOOOO|  X8
     |1 2 3 |1+2+3+|
      L L L  LRLRLR
      R R R  RLRLRL

1/4 S|O-O-|OOOO|  X8
     |1 + |1e+a|
      L L  LRLR
      R R  RLRL