Rotational sports take place in all 3 planes of motion, yet most of the traditional weight training programs take place in the sagittal plane.
This overlooks an opportunity to improve.
Vladimir Zatsiorsky talks about the delayed transmutation of qualities,
meaning you build qualities of strength and power in the off-season and then there is some amount of time that needs to take place to transfer them to sports specific qualities. It is essentially that question of I've put 50 lbs onto my squat in the off-season, when does that carryover to club head speed increasing?
This period is typically longer for those in rotational sports, because of the rotational component rather than a more linear task. 'Golfish' movements can allow you to bridge that gap between the general and specific and reduce that transmutation period.
If you live in bilateral stance, for example, you don't see the full benefits of t-spine mobility, hip stability, disassociation between upper and lower body, etc and often end up throwing more strength on top of dysfunction or leaving a stone unturned when it comes to improved golf performance.
In short, you reinforce your muscular imbalances.
Right handed golfers typically display adducted or internally rotated right hips, low right shoulders, left thoracic rotation and rib flare. These guys actually need more wrong side swings and med ball rotational drills, to manage these asymmetries, spending time in a bilateral stance squatting, pressing and pulling simply won't address this.
Further, In the golf swing as the hips start to shift into the downswing, the torso is still turning in the opposite direction to complete the backswing. Are you going to be able to prepare for this level of hip/torso separation by just squatting, and benching? It's not going to get the job done, you need to train with more specificity than that.
We often use 'bridging drills' to speed up that delayed transmutation curve when it comes to improvements in mobility, flexibility and disassociation carrying over to the golf swing. These drills can take many forms, such as backswing rotations in single-leg or bilateral stance with neutral spine, band resisted pivot and post drills, torso rotations with early extension feedback, shoulder external rotations in golf posture, etc.
However these interventions need to be appropriate to both the competitive schedule and to the individuals athletic ability. In all cases when a drill such as this is used a physical issue affecting the golfers swing will have been identified in conjunction with the swing coach, work will have been done in less demanding developmental positions to fix the issue and appropriate bridging drill is developed and put into use by both the fitness pro and the swing coach.
To paraphrase the great Dan John, don't mix the weight room and the sports field and if you're going to you had better be damn sure about it! This is why the involvement of the swing coach is absolutely vital.
SPECIFICITY OF POWER DEVELOPMENT
Golf has no chaos or reactive element so we can get fairly specific with regards planes and velocities of movement. Additionally, power development is plane specific and you can't necessarily expect a vertical jump or broad jump to carryover that well into your ability to generate force in the golf swing. I've seen way to many golfers (guys and girls) come into the gym, jump around half their height for a broad jump and then drive the ball close to 300 yards. I can't find anyone to attribute the quote below to (I found it in an old notebook), but it really sums this up quite nicely:
"We can't expect rotational power from linear modalities"
Additionally, In the golf swing each leg is performing independent actions in a number of planes which doesn’t carry happen in traditional bi-lateral sagittal exercises. Thus, the principal of specificity isn't being taken into account and if there is one thing I hate almost as much as golfers making swings on cable machines and calling it golf fitness, it's when the principal of specificity is ignored.
However, we do not need to tie a golf club to resistance bands to generate a more powerful swing. In fact, the more we do so the quicker faulty motor patterns arise and skills-based mechanics go down the drain. When it comes to strength and power development we should not mimic skills in the weight room. Rather, we should mimic movement patterns that will enhance a skill.
In the golf swing then we should be including power work which looks at independent leg action, different planes of motion along with different kinds of force generation (concentric, isometric, isometric).
In practice then, including some exercises such as tall kneeling SuperSpeed Golf swings, lateral bounds with external rotation, rotational med ball tosses, etc, at the appropriate time in the athlete's development (i.e. once a general movement and strength has been built and when the player is not in peak competitive schedule, if applicable) can close the transmutation gap when it comes to power development.
Video Credit: SuperSpeed Golf
Video credit: Eric Cressey
You'll notice none of these exercises particularly try to replicate the positions of the golf swing or involve adding load to the positions of the golf swing, but they do feature the same velocity, planes of movement and movement patterns as the golf swing, that is proper golf specific training!
In conclusion, be sure to develop a good base of general strength and power before progressing to more specific power generation work. This work should mimc the movement patterns and rate of force development seen in the golf swing, rather than the skill itself. If a physical limitation that is affecting a technical aspect of the swing has been observed then 'bridging drills' or mobility drills in positions highly specific to the golf swing can be utilised by the strength and conditioning coach in conjunction with the swing coach.