This is the second part of my instalment on the presentations I listened to at the Middlesex Student S&C Conference a few weeks ago!

I have written several times about Power.  Check out this blog here.  However, it is always great to hear people speak who are at the cutting edge of the research in strength and power development.

So it was great to listen to this next session.

Paul Comfort

Programme leader for the MSc Strength and Conditioning (University of Salford)

Head of Sports Science Support for Salford City Reds Rugby League Football Club.

Power and RFD Methods and Research

Study 1

Paul took his through the findings of his research in the J Strength Cond Res 25(12): 3269–3273, 2011.  This first study looked at variations of the Power Clean.  All variations were carried out at 60% of 1RM Power clean to determine force-velocity characteristics of each.  The variations included power clean from the floor, a power clean from hang (low), and two versions from the mid-thigh hang (high).

Findings:

• mid thigh clean pull (at 60% 1RM of Power clean) has highest value of Power (Watts), Force (Newtons) and Rate of Force Development (N/s)- see graph below

Discussion points:

• the reduced bar displacement  from a hang position requires greater acceleration of the bar
• Other research was cited which notes time to peak RFD during midthigh clean pulls, at all loads (30, 60, 90, 120% of 1RM Power Clean) was shorter (Peak at 30% 1RM, 99.8 milliseconds) than time to peak RFD in both vertical jumps (194.7  milliseconds) and countermovement jumps (263.3  milliseconds).

Application:

• the use of mid thigh power clean variations to develop Force may assist with the development of sprint speed.
• mid thigh clean pull and mid thigh power clean have practical benefit in that both are easy for less experienced athletes to learn and require less technical excellence.
• during a strength-based Mesocycle, it is suggested that the midthigh clean pull be used because this can be performed at loads >100% 1RM power clean, because the catch phase is not required.
• during a power-based Mesocycle, it is suggested that the midthigh power clean may be advantageous because it results in higher peak power output, peak Fz, and RFD compared with the other variations of the clean.

Study 2

Paul then took his through the findings of his second research study in the J Strength Cond Res 26(5): 1208–1214, 2012.  This study specifically looked at the force-velocity characteristics of the mid-thigh clean pull across a range of loads.

Findings:

• peak power occurred in mid thigh clean pull at a load of 40% 1RM of Power clean
• this corresponds to a bar velocity of 1.65 m/s
• peak force occurred in mid thigh clean pull at a load of 140% 1RM of Power clean
• peak rate of force development occurred in mid thigh clean pull at a load of 120% 1RM of Power clean

Comparison of peak bar velocity across loads

Seeing as there is a lot of current interest in velocity based resistance training it was interesting to note the velocity associated with the mid thigh clean pull during peak power.  According to Paul if you wanted to assess someone’s Power clean 1RM who can’t catch the bar it might be possible to use the weight which corresponds to approximately 1.25 m/s on the clean pull and use that as a guide to predict power clean 1RM!

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Peak Force across Loads

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Rate of Force Development across loads

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Peak Power across loads

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Discussion points:

• these findings are in contrast to the previous findings of Kawamori et al. (2006) who identified that peak power (2,228.9 6 192.3 W) was achieved at 60% of 1RM (power clean) when comparing loads of 30, 60, 90, 120% of 1RM
• peak power achieved at higher loads by Kawamori et al. (2006) is likely a result of the subjects being experienced collegiate weightlifters who may demonstrate a higher level of competence in such exercises
• at 140% 1RM there is a 69% decrease in velocity,  in contrast to only a 10.6% increase in Force!
• stronger individuals maximize power output at a different relative intensity than less strong individuals
• It is likely that the higher loads (70–80% 1RM) previously identified to elicit peak power output during the power clean and hang power clean are as a result of the additional phases of the clean (first pull and transition to mid thigh, or transition to mid thigh only) permitting greater time and range of motion to accelerate the bar before the second pull phase, technically unloading the bar because of its momentum
• the load that appears to elicit peak power output during this study is similar to the loads identified during the squat jump by Stone et al. (2003) of 40% 1RM

Application:

• when training to maximize peak power output, lower loads are recommended. Moreover if the goal is to train force, impulse or RFD higher loads, of 120– 140% 1RM, are recommended
• such exercises should be periodized to progress from max strength (Force) to peak power, in a sequential manner; therefore, it may be beneficial to begin at high loads (>100% 1RM) and progressively decrease loading to maximize velocity and power.

References

Kawamori, N, Rossi, SJ, Justice, BD, Haff, EE, Pistilli, EE, O’Bryant, HS, Stone, MH, and Haff, GG. Peak force and rate of force development during isometric and dynamic mid-thigh clean pulls performed at various intensities. J Strength Cond Res 20: 483–491, 2006.

Stone, MH, O’Bryant, HS, McCoy, L, Coglianese, R, Lehmkuhl, M, and Schilling, B. Power and maximum strength relationships during performance of dynamic and static weighted jumps. J Strength Cond Res 17: 140–147, 2003.