There’s no argument that the first serve is quite important on both the men’s and women’s tours. The percentages speak for themselves - the top servers on tour win about 3 out of every 4 points when the first one goes in and only about half the points when they miss the first serve. Those are the stats. And although spin, direction, patterns etc. have a lot to do with that, it seems that the bigger your serve, the more points you win.
Which brings me to the focus of this article. I recently started a 6-week pilot study to see if an overload throwing program can improve serve speed. More specifically, I’ll be throwing a weighted ball (similar to a medicine ball only smaller) twice per week and tracking serve speed on a weekly basis.
Why Weighted Throws?
You may be wondering...why weighted throws? It all started when I was looking through medicine ball (MB) research for tennis. Many coaches often use MB exercises to increase power output in groundstrokes - and to a lesser extent, the serve. There's even research to support MB use. For example, in one study, Genevois et al (2014) found a correlation between forehand (FH) ball speed and the one-handed MB forehand throw for distance. In other words, players who threw further could also generate more FH speed. That said, there was NO correlation between FH speed and the two-handed MB forehand throw for distance - which is generally what we as coaches use in practical settings (I know I have). It seems that the greater the specificity, the greater the transfer. This is even more true considering the 1.5kg one-handed throw had a greater correlation compared to heavier MBs (2kg, 3kg, 4kg and 5kg). Again, specificity principle at work.
But just because there’s a correlation, doesn’t mean that one form of training causes the other. Could it just be that players who have more power generating abilities are better at both MB throws and FH drives?
So then I looked at another study - a training intervention administered again by Genevois et al (2013). This was a 6-week study that compared 3 training groups. One group added a one-handed throwing program to their regular tennis training (just a quick note, all one-handed throws in both studies attempted to simulate the forehand stroke). Another group added weighted racquet training to their tennis training while the third group sticked to tennis training only. In terms of amount of weight, the one-handed MB throws were done with either a 2kg, 3kg or 4kg MB (depending on the strength level of the player) and weighted racquets were on average 11% heavier than the player’s regular racquets. So which group performed the best? The MB group! They increased their forehand drives by 11% over the 6-week period. The weighted racquets did ok too - they increased their forehand speeds by 5% while the regular training group had no improvement (i.e. they stayed put).
Are Medicine Ball Throws the Way to Go?
I have a couple comments to make about the above results. The first comment I have is in regards to accuracy - yes, the researchers also analyzed accuracy both pre and post, and the MB group fared the worst. It was about a 10% decrease over the 6-week period. Now this might not be too important during a preparatory phase, but closer to a big event (or series of events), you may want to reconsider your training routine. The weighted racquets group had no difference in accuracy while the regular tennis training group improved by about 8%. Until we know more about this topic, it might be best if we stick to mostly tennis play when approaching and playing events.
The second comment I have is in regards to the amount of weight that was added to the weighted racquet group. Remember, it was about 11% - the authors didn’t specify the exact weight of the racquets but they did mention that 30 grams was added. Here’s my point - the speed increases might have been even higher if more weight was added. Research on weighted baseball bat training have used loads that were about 10%-20% heavier than a regular bat and the best results were around the 20% overload mark.
Is Throwing Similar Enough to Serving?
Which brings me back to our initial question; why weighted throws? Well, if a MB one-handed throw is similar enough to a tennis forehand drive, then wouldn’t a weighted throw be similar enough (or perhaps more mechanically similar) to a tennis serve?
Although there are many mechanical differences between throwing and serving, Reid et al (2014) did find a moderately positive correlation between throwing velocity and serving velocity in a group of elite tennis players. This provides some decent evidence that throwing programs may be beneficial in improving serve speed.
Furthermore, there are now numerous studies outlining big performance gains with a weighted throwing program in pitchers. These studies have also experienced NO detrimental effects in pitching accuracy. And although, there are several baseball pitching & strength coaches that use a variety of weighted balls (from 20% underweight up to 120% overweight balls), research seems to point at the 20% mark as most effective.
The Research on Overload Throwing & Serve Speed
There has been one study that attempted to analyze serve velocity after weighted throws, and that was done by Ferrauti & Bastiaens (2007). This wasn’t a long-term training intervention but rather a PAP (post-activation potentiation) study. The researchers asked junior players to hit serves and in between sets of serves, to throw a weighted ball. One group threw a 600g ball and the other a 200g ball. The overload throwing (600g ball) group actually decreased serve speed while the underload throwing (200g) group saw no change. According to the authors, here’s why:
"We suggest two main possibilities to explain our contradicting results: (1) fatigue of the working muscles, and (2) temporary impairment of the intermuscular co-ordination."
I have a couple ideas myself. First, they were junior players. If you read my previous post on PAP you’d likely remember that for PAP to be effective athletes should first possess a good level of strength. These juniors had an average age of 12 - and although I’ve seen 12 year olds with good strength - it’s not common. Secondly, did you notice the weight of the balls? I probably should have told you that the average weight of their racquets was 282g. A 600g ball is 110% heavier than those poor kids racquets. Probably too heavy for juniors.
Keep in mind, this was not a long term training study, but rather a PAP study. To my knowledge, there hasn't been a single study to specifically analyze overload throwing and performance outcomes for serve speed. Based on this, and the above info, I'd say it's an area of research that deserves some attention.
Brief Overview of Pilot Study
In a nutshell, here’s what I’ll be doing. At the beginning of every week, I’ll be testing serve speed AND serve accuracy using methods previously outlined (Fernandez-Fernandez et al 2013). I will then perform maximal weighted throws twice (2) per week - the load will remain the same (about 20% heavier than my racquet) throughout the study, but the number of throws will vary from week to week. The key here is MAXIMAL. In all throwing studies, participants are asked to throw with the highest intent possible - sub-maximal throwing does have it's place, but in this case, it's max speed we're aiming for.
More details will follow in the coming weeks, but here's a preview:
Theory Behind Overload Training, Other Possible Benefits and Future Research Questions
We can trace weighted implement training back to the Soviets - they used varying weights and implements when training track & field athletes (primarily in the hammer throw & shot throw). It’s proposed that specific high velocity movements, like weighted throws, target fast-twitch muscle fibres and may alter the recruitment patterns of these high-threshold motor units. But the mechanisms at play are still not fully understood.
In baseball studies, no injuries have been reported with weighted implement training and some authors (along with coaches in the field) suggest that this type of training may in fact decrease injury risk. This theory is based on the force-velocity curve (learn more about this concept here). With weighted implements, you’re generating more force & less velocity than a typical throw, so training with heavier implements is more strength/force focused, BUT, that strength training effect is targeting a highly specific movement. This however, is only speculative at this point.
There are still many questions that must be answered on this topic. For instance, if positive adaptations do occur, when should this type of training be implemented and for how long? Does serve accuracy decrease, stay the same or improve? Do serve mechanics change? Should it be combined with other forms of implement training (like weighted racquets)? What loads are most appropriate? What's the ideal throw count per session? And more...
Hopefully this pilot study leads to future research on this topic...and other topics related to implement throwing and tennis performance. I'm sure it's an area that many coaches and players are interested in, as even small increases in power & speed, can have big outcomes on performance.