1	Strength Diagnosis
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3	Contents…
4	Maximal Power Defined This discussion will examine the maximum power output of the human. That which is produced during a single, maximum effort muscle action, which we will term “maximal muscular power”.
5	Why is Maximal Muscular Power Important? Maximal power output is the main determinant of performance in activities requiring one movement sequence with the goal of producing a high velocity at release, takeoff, or impact
6	Diminishing Time As athlete attempts to maximize explosive performance, the time over which can apply force and accelerate the body or object decreases
7	Three properties of neuromuscular system are paramount High maximal strength at changeover between eccentric and concentric contractions The ability to develop a large amount of force in a short period of time The ability of the muscle to continue to produce high force output as its velocity of shortening increases
8	Counter Movement Vertical Jump
9	Maximum Slow Velocity Strength Important during initiation of explosive movement or if a heavy load is to be accelerated According to force-velocity-power relationship velocity is very slow and not specific to most sport activities Power output is very low
10	Force-Velocity-Power Relationship
11	Heavy Resistance Strength Training Versus Lighter Resistance Explosive Power Training 7% improvement in vertical jump following 24 weeks of intense weight training Häkkinen & Komi (1985a) Explosive jumps produced significant improvement (mean 21% increase) in vertical jump Häkkinen & Komi (1985b) May be specific training adaptations to heavy resistance versus power-type training.
12	Heavy Versus Light…1 Heavy resistance strength training - improvements in maximal strength but increases are reduced at the higher velocities. Power training - lighter loads and higher velocities of muscle action - increases in force output at the higher velocities as well as the rate of force development.
13	Heavy Versus Light…2 Training response may not always follow the velocity specific training principle low levels of strength improvements throughout the force velocity spectrum regardless of the training load or style used
14	Conversion of Strength Gains simulation study effects of increased muscle strength on jump height initially decrease in height had to modify the control of the neuromuscular system in order to take full benefit of an increase in muscle strength, coordination needs to be adapted strength training must be followed by exercises, which allow the athletes to practice with their changed muscles Bobbert and Van Soest, 1994
15	Conversion of Strength Gains…2 Specific adaptations both neural and within the muscle cells to slow versus fast maximal movements One strategy is to increase muscle size and strength expression Then athlete practices skills in attempt to modify neural and cellular characteristics for specific movements - “tuning”
16	Some specific adaptations Rapid: Predominantly neural Both intra and inter muscular Slower: Protein expression Enzyme expression Muscle architecture Other structural changes? Importance of periodization
17	High Strength Not Enough? Too often we concentrate on maximum strength when training muscle But to be powerful, force must be applied at a fast velocity Explosive, powerful movements may involve the application of force for only a fraction of a second Athlete may not have sufficient time to reach maximum force capability
18	Rate of Force Development Power performance related to maxRFD Explosive type training increases maxRFD. Slow, heavy resistance training may even decrease maxRFD Athlete should try to develop force as rapidly as possible when training for power
19	RFD …2
20	Specificity of Training
21	Specificity of Training
22	Take-Home Point #2 Variety in training variables is crucial!
23	The Deceleration Phase and Traditional Weight Training Must decelerate resistance to stop at the end of range. This is undesirable for movements which attempt to maximize release or impact velocity. Further problem of energy absorption when attempting to complete the movement at a fast velocity.
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25	"Ballistic" Resistance Training The problem of the deceleration phase can be overcome if the athlete actually throws or jumps with the weight
26	Heavy Vs Light Loads The effect of heavy versus light load jump squats on strength, power and speed two groups of athletic subjects trained using ballistic jump squats at either a 30% or 80% 1RM load tested on sprint time, agility run, vertical jump, squat strength, squat jumps McBride et al., 1998
27	Heavy Vs Light Load - Results 80% training load decreased sprint performance increased strength increased force and power at 55% and 80% jump squats 30% training load borderline increase in sprint performance increased strength increased velocity and power at 30%, 55% and 80% loads
28	Implementing Ballistic Resistance Dumbell and barbell jumps onto box if need to reduce eccentric impact Weight stack machines Hydraulic and pneumatic machines (lack of feedback?) Olympic and modified Olympic lifts
29	Olympic Style Training
30	Future directions in training technology
31	Strength Qualities Certain strength measures represent specific or independent qualities of neuromuscular performance Both strength and speed-strength dimensions Specificity of these qualities is inherent to a particular sporting performance
32	Six Specific Strength Qualities Maximum strength Slow force speed-strength Fast force speed-strength Rate of force development Reactive strength Skill performance
33	Window of Adaptation Maximal muscular power has many components. Effective training should involve a "Mixed Methods" approach. The more developed a particular component is the smaller the window of adaptation. Greatest efficiency in training will be derived from targeting the components in which the athlete is most weak.
34	Window of Maximal Muscle Power Development
35	Determination of key performance characteristics Essential for achieving goals Biomechanical evaluation Analysis of high level athletes in that sport Tests (like training) must be specific “time is money” so only apply relevant tests
36	Test – Retest Cycle
37	Example test protocol: vertical jump sports Basketball, Volleyball, etc. Movement specific tests required for assessing qualities for horizontal movement Forward and lateral movements
38	Maximal Strength Isometric maximum 1RM squat Sub maximal 7-10 RM for 1RM prediction
39	Variables Force maximum Force maximum / body weight Measures of RFD – though limitations in isometric testing Dynamic RFD during both concentric and eccentric phases Not well researched at this stage
40	Relative or Absolute Measures? Both have application When athlete must move body weight then relative measure may be more important e.g. high jump When momentum is key then absolute measures may be more instructive e.g. rugby
41	Loaded Jump Squats Measure force and bar kinematics Calculate height, velocity, force and power output Concentric spectrum e.g. 30, 55, and 80% 1RM and/or Determine optimal load for power production
42	Determination of Optimal Load Adjust load in ballistic movements Results in changes in power output One load will produce highest power output
43	Optimal Load Load that elicits the highest mechanical power output Must consider total load moved i.e. include body weight if jumping Absolute force or % MVC or 1RM
44	Evaluating training by monitoring optimal load The load at which mechanical power is maximized shifts in response to training demands May provide a good tool for monitoring effects of periodization as well as detect overtraining, illness, staleness
45	Evaluating training program by monitoring optimal load…2
46	Counter movement jump Record ground reaction force as well as displacement Calculate: jump height peak velocity power output
47	Concentric jump Record ground reaction force as well as displacement Calculate: jump height peak velocity power output MDS/bw Impulse 100/bw mRFD Total impulse
48	Explosive Strength Measures…1 Maximal Rate of Force Development (mRFD) over a given period Usually between 5 and 100ms We use 30ms
49	Explosive Strength Measures…2 Index of Explosive Strength Effectively average rate of force development over entire movement
50	Explosive Strength Measures…3 Reactivity coefficient Effectively IES relative to body weight (W)
51	Explosive Strength Measures…4 S-gradient Starting force gradient Essentially RFD over first 50% of force increase
52	Explosive Strength Measures…5 A-gradient Quantifies RFD in late stages of explosive muscular efforts Essentially RFD over last 50% of force increase
53	Drop jumps Record ground reaction force as well as displacement Both jumps for maximum height and height while minimizing contact time – long and short SSC Test at 0.30, 0.45, 0.60, 0.75 m drop height
54	Drop Jumps…2 Calculate: jump height flight time contact time flight/contact time – reactive strength (RS) determine best drop height from highest RS
55	Drop Jumps…3 Best drop jump height Relationship to CMJ Changes with reactive strength training
56	Repeat jumps – power endurance Record ground reaction force as well as displacement Target time or number Calculate: jump height peak velocity power output change in these variables over set total work done average power output
57	Specific Tests Power output under fatigue and impacts Sport specific “obstacle courses” with time and heart rate Specific tests of lateral performance Highly sport specific tests e.g. Eccentric Strength Test
58	Eccentric Strength Test Maximum weight that can be lowered for back squat in a 4 second period
59	Eccentric Strength Test…2 Monitor force and bar velocity to ensure within test parameters
60	On a tight budget? 1RM for strength assessment Jump and reach or contact mat system for Countermovement Jump Concentric Jump Drop Jumps Contact mats or light gates – sport specific tests Standing broad jump 5 hop test Power clean Medicine ball throw
61	How to express the information Spreadsheet Calculate average and SD Report each variable as measurement and z-score Graph z-scores Identify relative weaknesses and strengths Adjust training program
62	What to look for Lack of progression of a target quality Sudden decline in a strength quality Imbalances between left and right
63	Assessing Imbalances Compare single leg vertical or broad jump 5 hop test Left and right sidestep Change of direction speed May indicate injury, muscle imbalance, or excessive handedness
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