Success Criteria & Constraints
What is a successful technique?
An important consideration for coaches and players is how a successful shot (shot quality) is identified and how successful the technique used is. Note that this may vary depending on the developmental stage of the player. 

The simplest measure of shot quality is to focus on the shuttlecock trajectory and landing location. Simple objective measures include:

Did the shuttlecock land in or out, or in the desired area on the side of the opposition of the court?
How small or large was the net clearance of the shuttlecock? For example, this should be minimal for a backhand low serve in doubles.
How quickly did the shuttlecock complete its trajectory? For example, trying to execute a fast smash stroke
How high did the shuttlecock reach during its trajectory? For example, a lift stroke.

When assessing shot quality at this basic level, one or all of the above criteria may be used.

Moving beyond this level of analysis becomes more complex when analysing shot quality, as tactical considerations become more apparent. Focussing on what the player does from a movement/technique perspective (spatio-temporal factors), several factors are of importance in determining how effective the technique is. This is due to how easily the opponent can anticipate the stroke based on their visual observation of the technique being performed, and at what point they can initiate their movement response. Consider the following:

Body Language – does the approach to the shot indicate that power will be generated? If the latter, then it may be possible that the opponent can eliminate possible strokes that could be played and therefore their positioning can be more informed and adjusted. This can also be used as an advanced deceptive technique (see later sections) where the body language may indicate a certain stroke to be played, and in the final moments, a different stroke is performed.

Body Positioning – similar to the above, the anatomical constraints of the body in certain positions may restrict the possibility of strokes available to a player. Consider a player playing a backhand from the rear court, with the shuttlecock close to the floor and with the arm close to full extension. Mechanically, it is unlikely that the player can develop sufficient shuttlecock speed to launch the shuttlecock to the opposition’s rear-court with sufficient height, and therefore the opposition can adjust their positioning where they will focus on the midcourt and forecourt areas.

Time Constraints – this includes the time given to a player (time pressure) that limits how much time they have to accelerate the racket head, and subsequently how much shuttlecock speed can be generated.

These factors provide information that may allow your opponent to gain a tactical advantage within a rally. It is important that good technique tries to minimise the amount of information available to an opponent as well as minimising the time prior to racket-shuttle impact in which they can respond to the shot that is eventually performed.

One important consideration is the use of a ‘common starting position‘, explored in more detail in future resources. It is crucial that from a given tactical situation e.g. constructive offensive forehand net zone, that all the possible strokes available to the player, share a similar starting position to prevent anticipation from the opponent. Only subtle and delayed (close to racket-shuttle impact) changes in technique are necessary in order to produce the different trajectories and speeds associated with various strokes.

From a movement and position perspective on the court, an overall technique that allows a player to effectively recover to an appropriate position on-court, in anticipation for the next stroke, is beneficial. Additionally, even If all the above criteria are met, the importance of having an awareness of the current tactical situation is crucial in determining the effectiveness of the stroke being played. This includes:

Awareness of the opponent’s positioning
Strengths/weaknesses of the opposing player, determined from prior experiences
The ability to be able to retrieve all possible return strokes

What constraints are placed on stroke success?

Similar to some of the above points regarding defining the shot quality, and determining success, it is important to also understand some of the constraints that may be placed on a player when executing techniques. Firstly, the amount of time given to the player from the preceding stroke places a time constraint on the technique, and consequently, the amount of time the complete a technique may be restricted, and thus certain strokes may not be available e.g. a fast flat lift from an opponent typically does not give a player sufficient time to complete a full-body rotational movement.

The positioning and control (balance) of the player will also impact how easily a technique can be executed, especially for complex motions in which coordination of multiple segments is required and production of high segmental rotational velocities e.g. overhead smash. Additionally, it is important how repeatable and adaptable a technique is, as small variations in body positioning and incoming shuttlecock trajectory will require small changes in technique to produce desired stroke outcomes. Finally, a player’s resistance to fatigue whereby the technical competencies are not reduced is a constraint placed on achieving shot success.
Technical Analysis
Could this be the future of Coaching?