Bowling action analysis: what to measure from video, phase by phase

The phases of a delivery and what to measure in each

Research on fast bowling times the action by a few key moments: the run-up, back-foot contact, front-foot contact and release, with the elbow judged over the last part of the arm swing. The table sets out what is worth measuring at each and what the studies have linked it to.

Which measurements go with pace, and which do not

The measurements with the clearest link to ball speed are run-up speed, how hard the front foot brakes, a front knee that stays firm through release, upper-trunk flexion and a bowling arm held back late. A 2024 systematic review of 15 studies reached much the same list by consensus: a quicker approach, an efficient, sequential conversion of linear momentum into rotation, quick deceleration in the delivery stride over a front knee kept extended from front-foot contact to release, and a bowling arm that comes through late (Bhandurge and colleagues, 2024).

Three measurements that are often watched show little or no link. Delivery stride length was tested in seven of the review’s studies, and only one found it related to ball speed. Vertical ground reaction force barely related to speed in the meta-analysis (r = 0.13). Shoulder counter-rotation showed virtually no correlation with speed in Australian Institute of Sport data (r = 0.009), the same data in which it emerged as the major technique factor behind lumbar stress fractures (Portus, 2001).

So a longer stride or a harder vertical landing is not a target for pace, and a twist of the shoulders is a warning sign rather than a source of speed. What the research says about changing technique, and about strength and sprint training, is in how to increase bowling speed.

Action type and the lower back

Back-foot contact is also where the action type is decided. On the Australian Institute of Sport criteria, an action is side-on, semi-open or front-on according to where the shoulders point when the back foot lands, provided the hips and shoulders are within 30° of each other then and the shoulders do not turn back 30° or more during the stride; break either condition and the action is mixed (Portus, 2001).

Counter-rotation’s link to lumbar stress fractures (Portus, 2001) has been replicated less consistently in newer studies (Farhart and colleagues, 2023). The thresholds, the injury evidence and how to classify your own action are in side-on vs front-on bowling actions.

Elbow extension: the legality question

Elbow extension is measured over a short window, from the moment the upper arm reaches horizontal until the ball leaves the hand. Under the ICC’s regulations the elbow may straighten by up to 15° in that window. What counts is how much the angle changes, so an arm that stays equally bent through the window is within the rule, and any movement past fully straight (hyperextension) is discounted.

The official test fails an action if any single delivery exceeds 15°, so an analysis should look hardest at the worst delivery, not the average. Only an ICC-accredited assessment is official. What phone footage can do is separate an action with a clear margin under 15° from one near enough to the limit to be worth testing formally. How to check if a bowling action is legal gives the frame-by-frame method, and the 15-degree rule explains what the ICC measures.

How to film a bowling action for analysis

Two views cover most of the action. A phone square to the pitch, side-on to the bowler, records the run-up, front knee, trunk and bowling arm; a second phone on the line of the pitch shows whether the hips and shoulders agree at back-foot contact. Use the highest frame rate the phone offers, ideally 120 or 240 fps and never below 60 fps, and film several deliveries at match pace off a full run-up rather than one.

Each question then has its own set-up. Classifying the action type relies on the view along the pitch, raised if possible: the method is in side-on vs front-on bowling actions. A legality self-check needs the side-on phone on the bowling-arm side and at least six of every delivery type you bowl, as set out in how to check if a bowling action is legal. Stance Cricket uses its own camera set-up, which differs from these views and is shown in our filming guide, and a Stance session needs at least two deliveries.

What one camera cannot tell you

A side-on phone suits the front knee, the trunk and the bowling arm, because they move across its picture. It is a poor judge of how far the hips and shoulders have turned, because that turn happens largely towards or away from the lens, the direction one camera reads worst. The phone on the line of the pitch fills that gap, with a blind spot of its own: side-on and semi-open look clearly different in it, but semi-open and front-on look much alike.

Some joints are hidden at the moments that matter. When the front arm crosses the chest, or the far leg passes behind the near one in the side-on view, tracking software has to infer those joints instead of seeing them, and an inferred position is less reliable. Where the camera stands, and how high, changes how often it happens.

Trust trends more than single readings. One knee or elbow angle read from one camera is an estimate; a change between sessions filmed from the same spot, at the same height and frame rate, is easier to rely on, so keep the set-up fixed and compare like with like. How markerless tracking works, and where it falls short of a laboratory, is explained in cricket biomechanics from video.

Bowling action analysis apps and tools

We make Stance Cricket, so read this section with that in mind. It describes types of tool in general terms, not any particular product. Tools of the same type differ and change, so check what an individual tool measures on its maker’s own site; we have not tested other tools’ accuracy.

Stance, our web app, measures run-up and delivery-stride mechanics and the elbow angle through the release window from phone footage, alongside the ball’s speed, line and length, calibrated from the stumps with no radar or sensor. You film with your phone’s own camera and upload in the browser, with nothing to install, and access is by waitlist while it is in closed beta. The elbow reading is information about your action, not an official ruling.

Apps built around body mechanics usually work from a slow-motion, side-on clip and report measurements of the action itself, such as the front leg, the trunk and the bowling arm; some accept more than one view of the same delivery. Check whether yours also reports ball speed.

Ball-tracking apps focus on the ball. From a phone on a tripod behind the stumps they usually report speed, swing, spin and pitch maps, and some add a few body measures such as arm angle. If the ball’s flight is your main question, one of these is the better choice; if you need joint angles through the action, check whether yours reports them.

Manual video-analysis software, some of it free and open source, lets you measure angles, distances and times by hand. It suits a careful front-knee or elbow check if you have the time.

How to choose a cricket analysis app walks through these types in more detail, and how Stance compares with other cricket apps sets out what Stance measures from one phone video.