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  1. Here's another image that Dr Kwon produced showing the typical 'in plane net force' (black vector arrow) applied via the mid-hand-point on the grip in the downswing. Now this is weird because it shows that force across the club in the downswing (from Top of Backswing TB -> ED club vertical) that creates a negative moment of force (torque) which will tend to rotate the clubhead clockwise (from a face-on view) and retain the lag angle between the clubshaft and lead arm. I don't think it's likely caused by the lead hand (although that might be possible) but probably via the trail hand as mentioned in Dr Sasho MacKenzie's videos. The problem is to try and explain what pro golfers could be doing to generate that net force across the club in the early downswing. Here again we have another idea of how lag angle can be retained via forces at the grip that may contribute to greater clubhead speed during release. There seems to be many different explanations for the creation of clubhead speed which, to be honest, can be very confusing. In my humble opinion, it all needs to be put together in some logical fashion if possible. 1. Faster Backswing (Dr Sasho MacKenzie) 2. Longer hand path to apply more linear work (Dr Sasho Mackenzie) 3. Create max hand speed earlier in the downswing (Athletic Motion Golf) 4. Creation of 'Stretch Shorten Cycles' at the joints from ground up using a kinematic sequence proximal to distal (Dr Greg Rose/Dr Phil Cheetham) 5. Optimised hand path (Dr Steven Nesbit) 6. Ground reaction forces tied in with a kinetic sequence 'Horizontal/Torque/Vertical' (Dr Scott Lynn) 7. Maximising the velocities of the arms/shoulders/ribcage/pelvis at the same time in the downswing (Dr Kwon) 8. Net force across the mid-hand-point to retain the lag angle as shown in Dr Sasho MacKenzie videos and Dr Kwon diagrams. 9. Active lead forearm rotation to increase clubhead speed (Dr Sasho Mackenzie research article) 10. The greater the fold (wrist cock) the more efficient the transfer of energy from the body to the club (Rod White). 11. The trail arm to create more force in the downswing (Dave Tutelman - Leecommotion, the Right-Side Swing (tutelman.com) Further, to create even more confusion there are research articles that: a. Could not find a kinematic sequence proclaimed in point 4 above (Speed Generation in the Golf Swing - Brady C Anderson) b. Could not find any energy being transferred between body segments in some proximal to distal sequence (Brady C Anderson). c. Some research says most of the work done by body segments is to move themselves, not get transferred between segments (Work and Power Analysis of the Golf Swing- Dr Steven Nesbit) d. Could not find any correlation between ground reaction forces and clubhead speed (Effect of Horizontal Ground Reaction Forces during the Golf Swing: Implications for the Development of Technical Solutions of Golf Swing Analysis :Maxime Bourgain, Christophe Sauret, Grégoire Prum, Laura Valdes-Tamayo, Olivier Rouillon, Patricia Thoreux, and Philippe Rouch). I apologise to any forum members about posting so many articles that require some background in science to understand, but I thought I'd amalgamate most of the possible explanations in one thread rather than piecemeal over multiple threads.
  2. I'd like to raise a question regarding what Dave Tutelman mentioned in his previous post: " During the downswing, move the hands along the hand path as fast as possible." How does this that tie in with the force velocity curve for muscle contraction (see below)? Doesn't this mean trying to move the arms/hands down the hand path as fast as possible will indirectly decrease the potential force the arms/hands can apply on the club? Doesn't this mean the golfer would be more likely to increase the magnitude of the force via his arms/hands, especially in the early downswing, if the golfer is moving the whole upper body/club unit (ie. torso/shoulders/arms/hands/club) with the core muscles that may move slower but be able to produce a higher force? -------------- What is the Force-Velocity Curve? Though the force-velocity curve may appear confusing and complicated, it is actually very straight-forward. The force-velocity curve is simply a relationship between force and velocity and can, therefore, be displayed on an x-y graph (Figure 1). The x-axis (i.e. horizontal axis) indicates velocity, for example, this may represent muscle contraction velocity, or velocity of movement (measured in meters per second). Whilst the y-axis (i.e. vertical axis) indicates force, for example, this may represent muscle contractile force, or the amount of ground reaction force produced (measured in Newtons). The curve itself shows an inverse relationship between force and velocity, meaning that an increase in force would cause a decrease in velocity and vice versa. Giving an example, a one repetition maximum (1RM) Back Squat would produce high levels of force but would be lifted at a slow velocity. While a countermovement jump (CMJ) would produce a high movement velocity, it would also only produce low-levels of force. This indicates that there is a trade-off between force and velocity. That being, when an exercise produces high levels of force, it will also produce a slow movement velocity and vice versa. This trade-off between force and velocity is thought to occur due to a decrease in the time available for cross bridges to be formed – more time, equals more cross bridges, and more cross bridges mean a greater contractile force (1). Therefore, slower velocity exercises allow the athlete to form more cross bridges and develop more force. Higher velocity exercises provide less time for cross bridges to form, and therefore results in lower force production. I thought I may as well add this AMG video too which provides some interesting comparisons between pros and amateurs and also how they increased the clubhead speed of a specific amateur (before and after). It seems that the amateurs perception of the golf swing was responsible for his smaller clubhead speed (ie. see below). 1. Leave hands up 2. Passive arms 3. Rotate hard
  3. Here's a better video discussing the ground reaction forces, the timing of the peaks in some kinetic sequence (Horizontal, Torque, Vertical) and also some tweaks one can do to try and modify the timing. Will be interesting to see some more recent videos of pros with their new Swing Catalyst dual plates which measure the ground reaction forces for each foot rather than the net effect in these graphs. I can also appreciate what IONEPUTT posted before when he said "I can also see how it could cause some major problems in consistency" For example, maybe too much 'lateral/torque/vertical' grfs (and even too much speed) might affect the golfers ability to hit the ball square on the sweet spot. Also , didn't Tiger previously snap his lead leg straight in the late downswing to generate clubhead speed? Makes one wonder whether that need for speed contributed to his knee injuries.
  4. Hi IONEPUTT I'm not sure it's as simple as that in the golf downswing (I wish it was!). If you have the book ' The Physics Of Golf' , Theodore Jorgensen provides a possible reason how a lateral movement of the hub of a double pendulum (used to model the golf swing) can cause an increase in clubhead speed. I did email Dr Scott Lynn about lateral movement caused by ground reaction forces and how they could influence clubhead speed and this was his reply: "Thanks so much for your email. You ask some really good questions that I don’t think anyone has the answers to yet. I’m not aware of any published work that has been done to date where the GRFs have been measured on the same swings where club inverse dynamics analyses were run so that the calculated club/hands kinetic values could be related to the measured GRFs. Hopefully this type of work will happen soon as this would really help our understanding of golf swing mechanics. My hypothesis would be that creating more horizontal braking GRF from the ground could result in some of that force (directed away from the target) being transferred through the body and to the club in the late downswing (as this is when we see the peak horizontal braking GRF in high speed swingers). It is interesting to note that in a few of the fastest long drive competitors in the world that I have had the opportunity to measure, the horizontal braking GRF peaks at the same time as the vertical GRF. If the golfer is able to peak the vertical and horizontal braking GRFs at the same time and transfer these forces through the body to the club, this could result in the net force on the club having a large magnitude and being directed more away from the target in the late downswing, thus increasing the moment arm between the line of action of the net force and the center for mass of the club. This would increase the in plane moment of force during the late downswing, when Dr. Mackenzie’s work has shown us that this particular moment is dominant in speeding up the club (the CoM of the club trying to “line up” with the line of action of that force vector). I have made a quick figure using one of Dr. Mackenzie’s animations to illustrate my point (see attached). If the purple vector is the net force applied to the club in the late downswing by a golfer with limited horizontal braking force, the blue vector would be my hypothesized net force vector applied to the club if horizontal braking GRF was increased in the late downswing. By using the horizontal braking GRF to lean this net force vector away from the target more, this would increase the moment arm distance (estimated in red…hard to do in 2D but you get the idea) and hence the in-plane moment of force and speed the club up as it heads into impact. Again this is just a hypothesis at this point and I’m open to other ideas and/or being proven wrong. "
  5. Hi Dave But what hand path is the optimal hand path? Say the golfer reaches the top of the backswing and then pulls his hands straight down as fast as possible, that could cause a positive MOF and early release. This is why I thought a good feeling for the golfer was to try and pull the grip off the shaft (from top of backswing all the way through impact) so that the net force applied via the mid-hand-point is directed closer to the COM of the club in the early-mid downswing (with a smaller moment arm to prevent early uncocking of the lead wrist). Basically, shouldn't the hand path in the early downswing be as least curved as possible to minimise divergence between the hand and club COM paths? For example, here is Jamie Sadlowski at the top of the backswing. If JS tried to pull his lead hand down as fast as possible in the direction of the red arrow he would early release unless he applied other forces to the grip to prevent that from happening. Obviously, I have exaggerated the scenario above, but if a golfer had a wrong perception of hand path and actually did the latter, you can see that the COM of the club would tend to rotate and try and align itself with the tail end of that red arrow net force vector. Therefore, a golfer, especially those that are not acquainted with the physics of the situation, may need guidance on how to optimise his/her hand path to prevent early release.
  6. Agreed, I don't think about this stuff when I swing and nor does Dr Sasho Mackenzie who basically uses external focus cues (he's a pretty good golfer).
  7. Dr Kwon explains how lateral movement horizontal ground reaction forces could be a factor to increasing angular momentum in the golfer, but no-one has confirmed 100% how a 'Happy Gilmore' type lateral motion (or even vertical ground reaction force) gets somehow transformed to optimal forces applied by/via the hands to the grip of the club which will ultimately increase clubhead speed. We seem to see patterns in ground reaction forces (like in the Mark Crossfield video) , that if somehow changed does seem to increase clubhead speed, so maybe it doesn't matter but I'd like to know the physics involved. Maybe the lateral motion is a precursor to increased vertical ground reaction force but what exactly is happening? How does it effect the timing, magnitude and direction of the forces applied via the hands on the grip? If we knew, then maybe golf instruction could be targeted better. PS. Even if we increased our clubhead speed , it won't guarantee we will hit the ball solidly, so it all has to be matched up.
  8. Here's another Mark Crossfield video demonstrating that what he's learnt regarding ground reaction forces seems to have changed his golf swing and significantly increased his clubhead speed.
  9. Found another interesting graph from one of Dr Kwon's you-tube videos (which seem to be attracting a lot of attention). You'll have to see the whole video to understand the swing events and phases. It portrays a typical swing graph pattern from golfers recorded on his 3D system (operating at 1000 Hz frequency). The section of the graph that I found interesting was between the 2 yellow pointer arrows (which I inserted myself) between the top of the backswing (TB) to just before lead arm horizontal in the downswing (EDA or P5 ). You can see that the angular velocity graphs of the shoulder line (SL) , Upper lead arm (UL) and the Club are all rotating virtually together as a unit up to the 'Release' point where the lead wrist starts to uncock. You can also see that 'Release' (uncocking of the lead wrist) at MC position starts happening just before lead arm horizontal (EDA/P5) and there doesn't seem to be much holding of the lag angle to later in the downswing. Maybe Jack Nicklaus was right when he said "you can't release the club too soon". I'm guessing you have to give yourself enough time to allow energy to be transferred to the club so it can angularly accelerate and optimise clubhead speed before impact. Personally, I can't even get my lead arm too far above horizontal in the backswing, so my ability to create lots of linear force in the early downswing using my upper body pivot is limited. I don't have much choice as I get older and less flexible but to use my shoulder girdle muscles more but still with the intention of pulling the grip off the shaft in the downswing in the early downswing to optimise the use of linear forces (ie. aligned more with the COM of the club).
  10. I personally have never actively tried to push up with the trail hand during the downswing, but maybe the upper body pivot rotates the framework unit of 'left arm/hinged wrist & folded trail arm/extended wrist' transferring some component of force (via the trail arm/hand) across the grip. I looked at Will Zalatoris swing in this video below and the COM of the club doesn't seem to go up at all during the downswing and quite different to Adam Scott. Maybe that's because Adam Scott pivots more in his backswing and gets his club shaft past horizontal. The Sasho MacKenzie video seems to offer a qualitative explanation of what forces cause the release of the golf swing. It's basically the net eccentric force applied across the grip (mainly a pull force via the lead arm) that helps angularly accelerate the club with no active wrist torque. Actually, the net wrist torque becomes negative in the later downswing which means the hands are being angularly dragged around approaching impact (because they cannot keep up with the increasing rotational speed of the club). There is a more detailed vimeo video below that offers a clearer explanation and also shows that the 'up' force (applied theoretically by the trail hand) can actually assist in the retention of the lag angle between shaft and lead arm in the early downswing. With regards how to increase clubhead speed , Dr Mackenzie has produced an article about that. How Amateur Golfers Deliver Energy to the Driver | Published in International Journal of Golf Science (golfsciencejournal.org) It's a long slog trying to read through all this stuff but basically most clubhead speed is caused by linear forces applied to the grip along the hand path. If I was trying to apply these 'linear force' ideas to increasing clubhead speed, I would personally be trying to feel as if I was pulling the grip off the shaft all the way through the downswing and through impact.
  11. This a bit of a techy post so won't make much sense to non-science forum members and it probably won't help improve your swing but might give you a different perspective of what could be happening. Been looking at some other stuff that the biomechanic experts have previously published and found some very strange things that didn't make much sense. This a video from Dr Sasho MacKenzie called 'Intro to Club Kinetics' and provided an example of the theorised hand forces that could be expected at the start of the downswing. So at the top of the backswing the right hand is pushing up more than the left hand is pulling down . This is true because the COM goes up as shown in Adam Scott downswing image below. The lead hand is pulling down with 190N which is about 43 lbs force which is quite large (imagine a weight of 3 stone approx). But the trail hand is pushing up with 200N which is about 45 lbs force and that seems difficult to comprehend. The trail hand is also supporting the weight of the 2 arms and the club which weigh approx 22lbs while also pushing up on the grip with an extra 23 lbs force. So Adam Scott is theoretically applying a total upwards force of 3+ stone weight which takes quite a lot of strength to do, even for a very small amount of time (ie. at the very start of the downswing). I've tried lifting my 22lb dumbbell over my head with a bent trail arm and found it almost impossible to do with just my shoulder girdle muscles . So, it does suggest that the whole upper torso also being utilised to help lever the bent trail arm/hand upwards for a short amount of time. Apparently, that extra trail hand force helps the club retain the lag angle between the lead arm and clubshaft preventing early casting/release. Again, this is non-intuitive because one would think that pulling with the lead hand while extra pushing with the trail hand would cause the club to cast (as if there was a pivot between the middle of the hands on the grip like a seesaw). See the graph (a) below which show the forces applied across the grip in the downswing by the right and left hand of a pro golfer (using sensors inserted in a specialised grip handle). Note that some of these graphs have been critically reviewed by Dave Tutelman in the below link (so the results could be questionable). Opening the loop -- instrumented grips (tutelman.com) For clarity I used a GEARS avatar and drew the forces and torques that each hand was theoretically applying ACROSS grip at the start of the downswing for this specific pro golfer being measured. The red force is the right hand push up across the grip while it's also applying a torque/twist in the clockwise direction, whereas the left hand (yellow force/torque arrows) is pulling down and also applying its own torque/twist in an anticlockwise direction. Note that I haven't shown the ultra important axial forces (reflected by graph 'b ) that are applied along the shaft which are mainly responsible for generating clubhead speed up to the point of release. When I look at the image above, it almost seems that the right hand is pushing the fleshy pad (ie. under the right thumb) against the left thumb but also using the fingers of the right hand to help retain clubhead lag angle with the lead arm. Basically the hands are working against each other with the left hand looking like it's trying to cast the club while the right hand is preventing it from doing so, but both could theoretically assist in applying forces more along the shaft at the same time. This particular golfer is primarily trying to pull the grip off the shaft in the downswing , while the right hand is being allowed to just get dragged along (see graph 'b'). Anyhow, this is just theoretical until more detailed research is conducted on a much larger sample of golfers rather than just a single pro golfer. As I implied before, this may not help with your golf swing, but it might change your perception on how it theoretically works.
  12. Here are a few good videos that may provide some drills (or external focus cues) but I think you will need to perform them correctly . It should help prevent you from spinning the trail hip too early provided you have added enough weight pressure on the trail hip/leg (at the top of your backswing) and have stretched the muscles as shown in the image further below. The next one below give you some info on how you use your obliques to initiate the movement of the ribcage in the downswing (from the ground up) and will probably help maintain your postural angles which can be compromised by spinning hips (because you usually end up with early extension and other correctional movements such as creating space to swing your arms/club to ball). The swing is about many parts so just fixing one link in the chain might not work unless they are all working well together. If you have several hours to spare , here is a theoretical explanation of the biomechanics of pelvic motion in the golf swing. How to Optimally Rotate the Pelv (perfectgolfswingreview.net) If you have too much weight on the lead leg/hip at the top of the backswing , then the above muscles cannot be optimally stretched. The weight pressure on the trail leg/hip joint will help stabilise the right side of your pelvis in space as you contract the above muscles at the start of the downswing (which will rotate your pelvis counterclockwise around a stabilised 'right leg/hip joint'. and stop it spinning out too early). Note that the contraction of these pelvic girdle rotary muscles only act for a short time in the early downswing (maybe until lead arm horizontal).
  13. Yes , there could be many reasons for an overly steep downswing so its best to look at the whole swing in its entirety to try and understand the cause and effect. Maybe your natural body type is suited to a steeper swing and it might not be a fault at all.
  14. Here's another article by Dr Phil Cheetham (this is just an abstract of his full dissertation) PhD Dissertation and Presentation The Relationship of Club Handle Twist Velocity to Selected Biomechanical Characteristics of the Golf Drive Abstract During the downswing all golfers must roll their forearms and twist the club handle in order to square the club face into impact. Anecdotally some instructors say that rapidly twisting the handle and quickly closing the club face is the best technique while others disagree and suggest the opposite. World class golfers have swings with a range of club handle twist velocities (HTV) from very slow to very fast and either method appears to create a successful swing. The purpose of this research was to discover the relationship between HTV at impact and selected body and club biomechanical characteristics during a driver swing. Three-dimensional motion analysis methods were used to capture the swings of 94 tour professionals. Pearson product-moment correlation was used to determine if a correlation existed between HTV and selected biomechanical characteristics. The total group was also divided into two sub-groups of 32, one group with the fastest HTV (Hi-HTV) and the other with the slowest HTV (Lo-HTV). Single factor ANOVAs were completed for HTV and each selected biomechanical parameter. No significant differences were found between the Hi-HTV and Lo-HTV groups for both clubhead speed and driving accuracy. Lead forearm supination velocity at impact was found to be significantly different between groups with the Hi-HTV group having a higher velocity. Lead wrist extension velocity at impact, while not being significantly different between groups was found to be positive in both groups, meaning that the lead wrist is extending at impact. Lead wrist ulnar deviation, lead wrist release and trail elbow extension velocities at maximum were not significantly different between groups. Pelvis rotation, thorax rotation, pelvis side bend and pelvis rotation at impact were all significantly different between groups, with the Lo-HTV group being more side bent tor the trail side and more open at impact. These results suggest that world class golfers can successfully use either the low or high HTV technique for a successful swing. From an instructional perspective it is important to be aware of the body posture and wrist/forearm motion differences between the two techniques so as to be consistent when teaching either method.
  15. Sorry but this is a long post: When you say loaded shaft , do you mean lag angle between lead arm and shaft? Not sure what you mean when you say "actual clubhead speed had very little to do with achieving max distance". Please see Dave Tutelman's website Smash Factor - Myths and Facts (tutelman.com) The 'Smash Factor' is defined as "the ratio of ball speed to clubhead speed" Here is an extract from his website showing the formula that relates to Smash Factor. Vball = Vclubhead 1 + e 1 + m/M cos(loft) * (1 - 0.14*miss) e = Coefficient of Restitution. For a modern driver this is pretty much stuck on 0.83, because (a) the USGA/R&A rules say it can't be more and (b) manufacturers know how to build to 0.83 and even higher. m = Ball mass. This is 46g, for pretty much the same reason as COR is 0.83. The rule says it can't be more, and less gives poorer performance. A lighter ball may have more initial ball speed, but its lower inertia gives it less "punch" through air resistance. Ball manufacturers learned long ago that heavier balls go farther, and the Rule makers learned almost as long ago to limit the maximum ball mass. So all balls are just about 46g. M = Clubhead mass. For most modern drivers, this is within a couple of grams of 200g. But it can depart significantly for design reasons. It is an unusual design that is far from 200g, but they exist. We'll explore this more below. loft is a property of the club. For most Tour drivers (and most drivers in the hands of amateurs) it is within a degree of 10º. But we will explore what happens when this varies. miss is the distance, in inches, that impact misses the sweet spot of the clubhead. It should be noted that the factor 0.14 dates back to about 1990, when driver heads were small and made of wood. Today's driver has a much higher clubhead moment of inertia, so the factor is correspondingly smaller. I haven't seen any data, but I suspect it is more like 0.07-0.10. As you can see velocity of the ball Vball is directly proportional to velocity of clubhead Vclubhead "The only way for a shaft to remain loaded and the wrists uncocking closer to the ball is by continued body rotation. Once rotation slows or stops, or if the arms move faster than the body, the wrists WILL release." ""Once rotation slows or stops, or if the arms move faster than the body, the wrists WILL release. It's simple physics, nothing can stop this from happening." Why should continued rotation of the body prevent the club from releasing ? I've read that it's the hand path vs clubhead path that is responsible for the passive uncocking of the lead wrist (unless you want to muscularly uncock your wrists)? I can see the value of continued rotation and not stalling because it would allow your trail shoulder to get closer to the ball so that you didn't 'run out of trail arm' . Unfortunately, the physics of the golf swing (especially to explain 'Release') is not very simple at all and the high tech equipment to find out what forces/torques are involved (via the hands) may be too expensive to research ( maybe millions of dollars). Some golf scientists and instructors still use the physics of the 'Driven Double Pendulum' and 'Centrifugal Force' to explain the golf swing in some pragmatic way but that is not the whole truth (it is more complex- see video below from Dr Sasho Mackenzie). It would get even more complicated if one tried to figure out the physics of how to square the clubface by impact . Dr Sasho MacKenzie has provided a possible mechanism through research which involves less muscular effort from the lead forearm to supinate in the late downswing. From 3D graphs of Tour Pros it's mainly the lead forearm rotation that squares the clubface, especially in the late downswing between P6.5-P7. A correct kinematic sequence from the ground up (if you can do it) seems to tally with what most 'Tour Pros' do ,but the time difference between the rotation of pelvis, torso/ribcage, shoulders, arms, wrists is still incredibly small for the 0.25-0.35 secs it takes during transition and downswing to impact. Also , if your like me and don't have much flexibility between the pelvis/torso and can't do that crunching side-bend that you see many golfers do , then its impossible for me not to go OTT with a dominant body driven golf swing, I have no option but to use my shoulder girdle muscles more dominantly to pull my arms down/out while just trying to get my body out of the way of my swinging arms/club.
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