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Thursday 6 January 2011

Speedendurance.com

Plyometrics, Ground Contact Time, and Sprinting (Part 1)

Posted: 06 Jan 2011 06:30 AM PST

Before I start discussing Plyometrics and Sprinting, I need to quickly review Ground Contact Times

Ralph Mann discussed this in detail at the 2007 USATF NPEP. More on Ralph Mann and his manual can be found here.

Basically, he said If you take a 10.20 100 meter sprinter, and reduce his ground contact time by 0.01 seconds, then the 45 strides can reduced his time to 9.75 seconds by shaving off 0.45 seconds. Good enough for an Olympic Bronze medal behind Usain Bolt and Tyson Gay?

Here is a study:

Sample Ground Contact Times based on Activity

Activity	Time (sec)
Walking	0.62
Jogging	0.26
Running	0.20
Sprinting	0.14

Source: AM J Sports Med. 1986 Nov-Dec; 14(6): 501-10.

Here is another study:

Another Sample Ground Contact Times based on Activity

Activity	Time (sec)
Standing Vertical Jump	0.50
Depth Jump off a 24" Box	0.20 – 0.40
High Jump Takeoff	0.14 – 0.20
Sprinting (Elite)	0.10

From the Scientific Report on the II World Championships in Athletics – Rome 1987 (IAF), mean velocity (m/s) and GCT (s) for each 10m section for Ben Johnson 9.83 and Carl Lewis 9.93. (cameras working at a frequency of 200 and 500 frames/sec). This race was the famous dual where Ben ran a 9.83 World Record but tested clean in the doping control following the race.

The above table shows ground contact between 0.08 and 0.09 seconds, well below the 0.10 threshold in the above study.

This obviously leads us to the next question: How do we decrease ground contact time from 0.08X to 0.07X seconds? How do we get there without losing speed?

Ground Contact Time, Stride Length and Fatigue in the 400m

What is the correlation between Ground Contact Time, Stride Length and Fatigue in the 400m?

The study was from "Incidenza dell'allenamento di forza su alcuni aspetti structurali delle prestazioni dei velocisti – esperienze degli allenatori della RDT" (Harmut Müller, Atleticastudi, 1, 1987 pp 25-58) and showed the kinetic parameters at 150m and 350m during a 400m race. The male subject was the 44.94 by Thomas Schönlebe and the female subject was the 48.56 by Marita Koch.

The 2nd 100 meter segment is considered the fastest of all four 100 meter segments in a 400 meters, with the 60-150 meter mark being the fastest. Thus the study used 150m and 350 meters as key markers.

Note how stride frequency does not change, but velocity, stride length and ground contact time degrades. (0.11 vs 0.14).

BONUS TIP: perhaps one should run the last 100 meters DIFFERENTLY than the initial 300 meters of a 400m? If so, be sure to read and listen to the Jared Deacon 400 meter Training Interview