Adarq.org

We concluded that 1) in short-term maximal exercise, performance depends on the capacity for using high-energy phosphates at the beginning of the exercise, and 2) the decrease in running speed begins when the high-energy phosphate stores are depleted and most of the energy must then be produced by glycolysis.

Nerve conduction velocity (NCV) has been shown to increase in response to a period of sprint training.

An increase in motoneuron excitability, as measured by the Hoffman reflex (H-reflex), has been reported to produce a more powerful muscular contraction,

 In contrast, stretch reflexes appear to be enhanced in sprint athletes possibly because of increased muscle spindle sensitivity as a result of sprint training.

Fatigue of neural origin both during and following sprint exercise has implications with respect to optimising training frequency and volume.

Although muscle power is needed for acceleration and maintaining a maximal velocity in sprint performance, high leg stiffness may be needed for high running speed. The ability to produce a stiff rebound during the maximal running velocity could be explored by measuring the stiffness of a rebound during a vertical jump.

The results from this investigation question the advocacy of removing the false step to improve an athlete's sprint performance over short distances. In fact, if the distance to be traveled is as little as 0.5 m in the forward direction, adopting a starting technique in which a step backward is employed may result in superior performance.

The results indicate a positive contribution to the force and power from a step backwards. We advocate developing a training program with special attention to the phenomenon step backwards.

The HV (HIGH VELOCITY) group improved significantly in total 100 m time (P < 0.05 compared with the RUN and PAS groups (CONTROL GROUPS)). The HR (HIGH RESISTANCE) program resulted in an improved initial acceleration phase (P < 0.05 compared with PAS).

Compared with the 4.7 degrees slope, the 5.8 degrees slope yielded a 0.10-s faster 40-yd sprint time, resulting in a 1.9% increase in speed. CONCLUSIONS: Those who train athletes for speed should use or develop overspeed hills with slopes of approximately 5.8 degrees to maximize acute sprinting speed. The results of this study bring into question previous recommendations to use hills of 3 degrees downhill slope for this form of overspeed training.

Elastic-cord tow training resulted in significant acute changes in sprint kinematics in the acceleration phase of an MS that do not appear to be sprint specific.

The concentric half-squats were related to 100 m (r=0.74, p<0.001) and to the mean speed of each phase (R=0.75, p<0.01). The counter movement jump was related to 100 m (r=0.57, p<0.05) and was the predictor of the first phase (r=0.66, p<0.01). The hopping test was the predictor of the two last phases (R=0.66, p<0.05). Athletes who had the greatest leg stiffness (G1) produced the highest acceleration between the first and the second phases, and presented a deceleration between the second and the third ones. CONCLUSIONS: The concentric half-squats test was the best predictor in the 100 m sprint. Leg stiffness plays a major role in the second phase.

Immediately following the start action, the powerful extensions of the hip, knee and ankle joints are the main accelerators of body mass. However, the hamstrings, the m. adductor magnus and the m. gluteus maximus are considered to make the most important contribution in producing the highest levels of speed.

Maximum running speed and step rate were increased significantly (p < 0.05) in a 35-m running test after training by 0.29 m.s(-1) (3.5%) and 0.14 Hz (3.4%) for the combined uphill-downhill group and by 0.09 m.s(-1) (1.1%) and 0.03 Hz (2.4%) for the downhill group, whereas flight time shortened only for the combined uphill-downhill training group by 6 milliseconds (4.3%)...It can be suggested that the novel combined uphill-downhill training method is significantly more effective in improving the maximum running velocity at 35 m and the associated horizontal kinematic characteristics of sprint running than the other training methods are.

Pearson correlation analysis revealed that the single best predictor of starting performance (2.5 m time) was the peak force (relative to bodyweight) generated during a jump from a 120 degree knee angle (concentric contraction) (r = 0.86, p = 0.0001). The single best correlate of maximum sprinting speed was the force applied at 100 ms (relative to bodyweight) from the start of a loaded jumping action (concentric contraction) (r = 0.80, p = 0.0001). SSC measures and maximum absolute strength were more related to maximum sprinting speed than starting ability.

Muscle thickness was similar between groups for vastus lateralis and gastrocnemius medialis, but S10 had a significantly greater gastrocnemius lateralis muscle thickness. S10 also had a greater muscle thickness in the upper portion of the thigh, which, given similar limb lengths, demonstrates an altered "muscle shape." Pennation angle was always less in S10 than in S11. In all muscles, S10 had significantly greater fascicle length than did S11, which significantly correlated with 100-m best performance (r values from -0.40 to -0.57). It is concluded that longer fascicle length is associated with greater sprinting performance.

An argument is presented that suggests that, in response to voluntary effort, the range of discharge rates of each motor-unit pool is limited to those only just sufficient to produce maximum force in each motor unit.

Results: As expected, knee extension strength in the trained weight lifters (367.0 +/- 72.0 N) was significantly greater than that in the control subjects (299.9 +/- 35.9 N;P < 0.05). Motor unit discharge rates were similar in the two subject groups at the 50% MVC force level (P > 0.05), but maximal (100% MVC) motor unit discharge rate in the weight lifters (23.8 +/- 7.71 pps) was significantly greater than that in the age-matched controls (19.1 +/- 6.29 pps;P < 0.05).

In response to resistance training, maximal voluntary force increased 25% in young and 33% in older subjects (P < 0.001). Maximal MUDR increased significantly (11% young, 23% older) on day 2 [F(3,36) = 2.58, P < 0.05], but in older subjects returned to baseline levels thereafter.

The single unit EMG recordings suggest that, in sustained and repeated submaximal contractions, muscle contractile failure is compensated by recruitment of additional motor units rather than by rate coding of those already active. During intermittent contractions large increases in the surface EMG were associated with only modest increases in firing rates. In sustained contractions when the EMG was held constant the discharge rates declined in parallel with the force. In constant force contractions involving about 35% muscle contractile failure no changes in discharge rates were seen despite substantial increases in EMG.

Research I have seen has suggested non-fatigue inducing compound movements near 90% 1RM to produce a short term potentiation effect vs. you & kellyb's recommendation of a high intensity set + full recovery wait time. Have you attempted to correlate the difference in power output between your version and a shorter more 'conventional' potentiation method?

I would have to agree that for conditioining, the 8 min rule is very effective when you have more than 2 exercises. 

This brings up another issue. If we look to optimize CNS recovery and the potentiation affects of depth drops, say in conjuction with a top speed workout, then we are looking at potentially 16mins before hitting depth jumps for a second time. Optimal for potentiation, maybe, but I dont think it's all that practical from a time standpoint; especially in a team environment. I think a 16 min setup may work very well just prior to a championship competition.

That being said, depth jumps also serve as a tool to learn how to manipulate force. If force manipulation and movement efficiency are the goal, then waiting for the full potentiation effects of the depth jumps may not be neccasary. I'm not up on the details, but I would think that the full potentiation effects could be manipulated by changing the variables, like drop height or as in with AMT, the acceleration. If the height of the drop is sub optimal in order to ingrain the movement patterns, then I think you gain some potentiation with also the learning aspect.

And now I forgot where I was going with this.....more to come later, I hope.