What Elite Throwers Know About Developing Rotational Power

Imagine hoisting a 16-pound bowling ball to your shoulders and, with one arm, heaving it 77 feet, 2 inches. Then attach a 3-foot, 2-inch wire to it, swing it around a few times, and heave it 284 feet. Now take a dinner serving plate that weighs 4.4 pounds and toss it 243 feet. Those numbers represent the men’s world records in the shot put, hammer throw, and discus—that’s power!

As a weightlifter and weightlifting coach, I’ve always been interested in throwers because they often perform weightlifting movements, and a few go on to become elite weightlifters. I lived in Northern California in the 1970s and early 80s, and among the most remarkable dual-sport power athletes here were Ken Patera, Bruce Wilhelm, and Al Feuerbach.

Patera and Wilhelm trained at the Sports Palace Gym in San Francisco under Coach Jim Schmitz. Schmitz, my first and only coach, was a three-time Olympic Games coach and had a knack for getting the most out of big men. Patera placed sixth in the shot put in the 1968 Olympic Trials and had a best of 64-7 (19.7m) when the world record was 69-2 (21m).

As a weightlifter and weightlifting coach, I’ve always been interested in throwers because they often perform weightlifting movements, and a few go on to become elite weightlifters, says Kim Goss. Share on X

Patera moved on from track to compete in the 1972 Olympics in weightlifting, was the first American to clean and jerk 500 pounds, and was the only American to Olympic press 500 pounds. Although Russia’s Vasily Alexeev was the first to clean and jerk 500 pounds in 1970, six months before that historic lift, Patera cleaned 500 but missed the jerk when the platform collapsed.

Wilhelm placed fifth in the shot put in the 1972 Olympic Trials, fifth in weightlifting in the 1976 Olympics, and became the first American to snatch 400 pounds. Wilhelm’s best official shot put was 66-1.4 (20.12m), and he unofficially hit 68-9 (21m).

Feuerbach trained at the San Jose YMCA in San Jose, California, where I worked as a Nautilus instructor (yeah, I know). A three-time Olympian (counting the boycotted 1980 Games), Feuerbach established a world record shot put of 71-7 (21.82m). He made this historic mark on May 5, 1973, during the San Jose Invitational at San Jose State College. Five weeks later, Feuerbach placed second in the Senior National Weightlifting Championships in the 242-pound bodyweight class. He won the meet the following year, snatching 341 pounds and clean and jerking 418.

There were many other elite throwers in Northern California who could have excelled in weightlifting competitions. For example, I often trained at the Iron Works Gym in San Jose, where I saw Olympians Mac Wilkins and Brian Oldfield train. Wilkins was the 1976 Olympic champion and broke the official world record in the discus four times. Oldfield put the shot a world record of 75 feet (22.86m) as a professional. Wilkins and Oldfield were physically impressive and as strong as they looked.

In one workout, I saw Wilkins easily snatch 308 pounds (I heard his best was 330), and the May 1973 issue of Strength and Health magazine has an early photo of Oldfield clean and jerking 350 pounds in competition. I asked Oldfield what he thought the best lift was for the shot put. His answer was the Olympic press, which was dropped from weightlifting competitions after the 1972 Olympics. Oldfield practiced what he preached and became exceptionally powerful in overhead movements—he reportedly could push press over 400 pounds.

Having watched several elite throwers train and coached a few who competed at the collegiate and post-collegiate levels over the past four decades, I’d like to share six key points I’ve discovered.

1. Mass vs. Class

Except for a few phenoms, such as Feuerbach, who stood 6-1, elite throwers tend to be exceptionally tall. Consider the heights of the 2024 gold medal winners in the Olympics:

If there is an exception to the “taller is better” rule, it would be the hammer throw. The current world record in this event is held by two-time Olympic Champion Yuriy Sedykh, who threw 284-6 3/4 (86.74m) in 1986. He stands 6-1. The US record is held by three-time Olympian Rudy Winkler at 271-4 (82.71m). Winkler is 6-2. On the women’s side, Anita Wlodarczyk of Poland holds the world record at 272-2 3/4 (82.98m). Wlodarczyzk is a three-time Olympic gold medalist and is considered the greatest female hammer thrower ever. She is 5-9.

While this discussion primarily focuses on male throwers, I would like to share my thoughts on training female throwers.

2. The Fabulous Females

My weightlifting background enabled me to coach several remarkable female throwers in the 80s and 90s. What I want you to consider is that a large increase in body mass may not be necessary to achieve optimal performance, at least for female throwers.

My weightlifting background enabled me to coach several remarkable female throwers. I want you to consider that a large increase in body mass may not be necessary to optimal performance, at least for female throwers, says Kim Goss. Share on X

Okay, storytime—after serving a four-year Air Force tour (1978-82), I returned to Northern California to finish my undergraduate degree at California State University, Hayward. While there, I enrolled in Dr. Don Chu’s weight training class. Dr. Chu is best known for his work in plyometrics, but his resume as a jump coach includes 45 All-Americans and 17 national champions. As a result, his PE class attracted several high-level track and field athletes. One was Glenda Ford, a discus thrower and shot putter.

Ford was already an exceptional powerlifter, having done a 358-pound squat in competition (credit to Gary Hunnicutt for coaching her in this lift). Thanks to her coach, Dr. Harmon Brown, she also had exceptional throwing technique. When I met her, Ford had set an NCAA Division II record with a winning throw of 162-1 (49.4m) at the 1983 national championships. At this time, I introduced Ford to the full lifts.

Ford improved to 181-7 (55.2m) the following year, which is especially impressive considering her relatively light bodyweight. “She was the best discus thrower in the country for her size,” says Brown. Ford was also, pound-for-pound, an excellent weightlifter.

Ford competed in the 148-pound bodyweight class and broke an unofficial world record in the snatch at the 1985 Senior National Weightlifting Championships. She also placed fourth in the World Weightlifting Championships.

Another powerful athlete I coached, but only after she retired from throwing, was Lindsey Spencer. She had represented Utah State, and her PRs include 178-9 (54.48m) in the discus, 203-4 (61.99m) in the hammer, and 48-11.75 (14.93m) in the shot put. About ten years ago, Spencer moved to Rhode Island to work with me on the Olympic lifts (see video 1).

Spencer’s athleticism and explosiveness remind us that throwers are athletes, and this athleticism transfers to the lifting platform. After just four months of training, she officially broke the New England record in the clean and jerk, lifting 223 pounds in the clean and jerk at the 2014 Arnold Championships. From there, Spencer competed at an elite level in raw powerlifting (squat 419.9 pounds, bench 248, deadlift 440.9 at a bodyweight of 185 pounds) and went to battle in the octagon in MMA.

Video 1. Lindsey Spencer was an elite college thrower who went on to compete at a high level in weightlifting, powerlifting, and MMA.

At a world-class level, I want to mention two more female throwers: Carol Cady and Suzy Powell-Roos. Both broke American records in the discus and used weightlifting as their primary method of strength training.

Cady broke the American record in the discus with 216-8 (66.1m) and unofficial American records in the hammer throw (as it was not an official event at the time). Cady then broke all the American weightlifting records in the 181-pound bodyweight class and competed in the World Weightlifting Championships.

As for Suzy Powell-Roos, I did a feature on her for the Summer 2000 issue of BFS magazine when she was pursuing Cady’s American record. Her strength coach at the time was John McBride of the University of the Pacific.

“He [McBride] gave me my first real introduction to weightlifting,” says Powell-Roos. “He showed me how to do cleans and snatches.” The result? Powell-Roos competed in the 1996, 2000, and 2008 Olympics. In 2007, she threw 222 (67.67m) to break Cady’s long-standing record, and in 2007 hit 227-82 (69.44m). She competed at a bodyweight of 174 pounds.

All these athletes mentioned so far, both male and female, were relatively lean. Could they have thrown farther if they had increased their bodyweight, even if the additional mass was not muscle?

Except for a few phenoms, such as Feuerbach, who stood 6-1, elite throwers tend to be exceptionally tall. If there is an exception to the ‘taller is better’ rule, it would be the hammer throw, says Kim Goss. Share on X

3. You Can’t Flex Fat

In the 1970s, I trained and worked at Bob’s Health Club in Fremont, California (being paid with tubs of protein powder—seriously). I saw the owner, Bob Perata, take a member’s arm measurements with his arm held straight down, which I thought was odd. When I asked my boss why he didn’t have the member flex his biceps to take the measurement, he repeated a motto Arnold Schwarzenegger made popular, “Because you can’t flex fat!” Likewise, throwers must question the value of adding fat mass for the sake of adding fat mass.

Although the data from this study on high-level throwers is from the 70s and 80s, it’s interesting that the researchers concluded, “On average, male throwers had a body fat of 15.9 percent, while females had a percent body fat of 25.4 percent.” These numbers are far below the averages of most Americans, not that the average bodyfat levels of most Americans are optimal. That said, being healthy is one thing, and achieving peak performance is another.

I haven’t found any studies on how adding fat mass directly affects throwing performance. However, we can infer some conclusions from observing weightlifters who move up bodyweight classes and become less efficient. In the following example, I selected weightlifters over powerlifters beyond just having a single set of standardized rules for competition. Let me explain.

Yes, powerlifters are strong, with 1,000-pound squats and deadlifts becoming commonplace. However, speed is a component of the power equation. In powerlifting (PL), power output decreases significantly with heavier weights because movement speed decreases. “Thus, there is an inverse relationship between power output and performance in competitive PL,” says biomechanics researcher Dr. John Garhammer. Let me share a real-world example of why weightlifting is better than powerlifting, at least at the higher performance levels.

I met Grace Apiafi from Nigeria in Colorado Springs in 1987. She had put the shot 43-4 (13.24m) in the 1979 African Championships and then retired. About six months before the 1988 Olympics, Apiafi told me she wanted to make the Olympic team. Besides being detrained from a strength training perspective, her primary fitness training for the previous three years was teaching aerobic dance to school children. Further, in her competitive days, the power lifts were her primary method of strength training.

After such a long layoff and having a few months to get her ready for her Olympic Trials, it would be difficult to get Apiafi’s strength back to her previous levels in the powerlifts. Instead, I had her focus on weightlifting, and she even competed in a weightlifting meet we held at the Air Force Academy. Apiafi not only made the Olympic team but also set a personal record in the shot at 49-4 (15.06m), a six-foot improvement. Success leaves clues.

Getting back to my bodyfat example, consider that in 1984, Russia’s Anatoly Pisarenko clean and jerked 584.2 pounds, an absolute world record. In 2021, Georgia’s Lasha Talakhadze clean and jerked 588.6 pounds, the current world record. Crunching the numbers, it took 37 years to increase the record by 4.4 pounds. A victory is a victory, but at what cost?

Pisarenko’s bodyweight was about 271 pounds. Talakhadze has weighed as much as 403 pounds, a difference of 132 pounds. Was that much additional bodyweight, much of it in the form of fat, necessary for Talakhadze to lift the all-time record—or are we looking at a dramatic case of diminishing returns?

Based on a paper he published in 2002, Russian sports scientist Igor Abramovsky would say Talakhadze’s additional fat mass may have been unnecessary “because the weightlifter has to lift this excess weight during the execution of the weightlifting exercises; second, the sportsman’s speed deteriorates.” Further, in a 1985 medical symposium, researchers estimated that a bodyweight over 308 pounds results in a point of diminishing returns for a weightlifter. There is also the issue of the added mass adversely affecting lifting technique.

According to weightlifting sports scientist Bud Charniga, “The combined girth of the belly and thighs of the biggest athletes conspire to force the athlete to fix the weight higher, i.e., creating a less stable center of mass of athlete – barbell unit.” Expanding on Charniga’s statement, more weight can be lifted to a lower height, so having to catch the barbell in a higher position reduces how much a weightlifter can lift. Excessive fat mass is especially problematic for women.

According to Charniga, compared to male lifters, female lifters “have smaller bones, comparatively less muscle mass and proportionally greater fat mass than their male counterparts. Consequently, with the rise in bodyweight in excess of the now 90 kg (198 pounds) border, females will tend to add more fat mass relative to the increase in muscle mass.”

How can you tell when enough muscle mass and total bodyweight is enough for a shot putter, discus thrower, or hammer thrower? And how should strength training workouts for throwers be designed? I have some ideas.

4. The Switch to Fast Twitch

You will hear bodybuilding writers use terms such as muscle maturity, muscle fullness, muscle density, and muscle hardness—I have no idea what they are talking about. What I do know is that throwers should be most concerned with how their muscles perform, not how they look.

Consider the following conclusion from a 2022 study published in the International Journal of Exercise Science: “Shot put performance depends on the development of maximal force in minimal time.” So, a better question is not how much muscle a thrower needs to pack on their frame, but “Which muscle fibers produce the most powerful muscular contractions?”

There are two basic types of muscle fibers: Type I (slow twitch) and Type II (fast twitch). Type I fibers are less powerful than Type II fibers but have greater endurance. Bodybuilders primarily use submaximal weights and higher repetitions, which develops the Type I fibers more than the Type II. These lower-intensity workouts also increase the development of non-contractile substances and fluid, further increasing overall muscle size. This explains why bodybuilders are strong but seldom as powerful as weightlifters or throwers.

I should mention here that although some throwers used plyometrics to develop fast twitch muscles, they often avoid the more intense forms of these exercises, particularly depth jumps. And as with adding body mass, there is also the matter of diminishing returns.

Anatoliy Bondarchuk won Olympic gold in the hammer throw and has coached many champions, including Yuri Sedykh. Bondarchuk saw significant decreases in the correlation between jumping ability (long jump, triple jump, vertical jump) as hammer throwers increased their results. Although plyometrics may have value for beginners, advanced throwers may not benefit as much. Risk of injury is another issue.

While coaching at Brown University, one of my athletes was Kaela Brenner, a cross-country athlete. Her father was John Brenner, who broke the American record shot put with 73 feet, 10-1/2 inches (22.52m), and won a bronze medal in the 1987 World Championships. Brenner said his training was going well, and he told a Los Angeles Times reporter he expected “to go 74, or 75 feet in a meet.” On a visit to Brown University to visit his daughter, Brenner told me he missed the 1988 Olympics when he attempted a depth jump at the UCLA weight room, tearing his patella tendon on his left knee.

One practical way to determine whether a thrower is on the right track with their training is to test athletes with the Lewis Formula, a power index based on vertical jump and body weight. The vertical jump is the X axis, and the athlete’s bodyweight is the Y. The point where they intersect represents power.

As long as a thrower’s Lewis Formula increases, we can “assume” that the athlete can continue increasing their bodyweight (although, preferably, with lean muscle mass). If their power index is not improving, the athlete and their coaches must find ways to increase their vertical jump or decrease their body mass without losing strength, such as by reducing body fat.

I haven’t found any studies on how adding fat mass directly affects throwing performance. However, we can infer some conclusions from observing weightlifters who move up bodyweight classes and become less efficient, says Kim Goss. Share on X

Of the three types of throwers discussed here, my understanding of the work of Olympic Games hammer throw champion Anatoliy Bondarchuk is that the vertical jump has the highest correlation to the shot put and the lowest correlation to the hammer throw. (For an extensive review of this topic, I highly recommend Bondarchuk’s classic textbook, Transfer of Training in Sports. I would also recommend attending seminars by Derek Woodske, a strength coach I worked with for several years in Rhode Island. Woodske threw the hammer 242-09 (73.79m) and has an extensive understanding of Bondarchuk’s work.)

I’ve also talked to track and field coaches who found that some of their throwers could vertical jump higher than their high jumpers (due to the type of stretch-shortening cycles that occur in the two sports). Just how high can shot putters jump? Here are a few impressive examples:

By the way, Nelson claims to have push jerked 440 for two reps. I recall early work by biomechanics researcher Dr. John Garhammer, who said the power outputs of the push jerk were as high as the highest power outputs of the clean. Perhaps Nelson’s emphasis on this lift contributed to his remarkable jumping ability.

Besides developing a foundation of strength with the powerlifts and explosiveness with weightlifting movements, throwers often perform specific exercises that improve rotational power. Before addressing this issue, it would be wise to consider what’s going on with the feet.

5. Foundations of Power

A house needs to be built on a solid foundation, and likewise, a thrower must have a stable foundation from which to produce rotational force. Let’s begin with some definitions.

“Valgus and varus feet are conditions where the ankle bones do not rest directly above the foot,” says Posturologist and Strength Coach Paul Gagné. He says a valgus foot is characterized by the foot collapsing inward (pronation), causing the ankle bones to rotate internally. There are three levels of the valgus foot, with level three fulfilling the definition of flat feet.

A varus foot, in contrast, causes the foot to collapse outward (supination), causing the ankle bones to rotate externally. “Excessive valgus and varus feet increase the stress on the ligaments of the ankle, knees, and lower back,” says Gagné. “Regardless of how many stretches and corrective strength exercises you do, they will have little effect on improving posture if your feet are not structurally sound.”

Another important foot condition is disharmonic feet, where one foot is valgus and the other is varus (Image 6). “Disharmonic feet shift the pelvis, increasing the shearing force on the spine,” says Gagné. “As it relates to throwing, an athlete with disharmonic feet will carry more weight on one leg, and this shift in balance will affect their ability to generate force in a rotational direction.”

Although beyond the scope of this article, Gagné says that valgus, varus, and disharmonic feet can be improved with special eye exercises and corrective exercises that reform the foot arch. He says the extensor hallucis longus and the flexor hallucis longus are among the most important muscles to strengthen. Image 6 shows an exercise Gagné prescribes to athletes that aligns the knee with the big toe and creates lateral tension on the feet to lift the arch and help correct valgus feet.

Two elite throwers who benefited from corrective exercises are Adam Nelson and four-time Olympian Jud Logan, a hammer thrower. Both athletes worked with Canadian strength coach Charles R. Poliquin.

When I interviewed Nelson in 2004 for BFS magazine, he said Poliquin corrected muscle imbalances that contributed to his shoulder problems, whereas Poliquin wrote that he was able to resolve Logan’s chronic knee pain by correcting muscle imbalances in his quadriceps muscles.

6. Twist and Shout

In contrast to general exercises that develop overall strength or power, such as the squat and the snatch, there are special exercises that overload the muscles in movement patterns similar to those produced in the sport. However, we must be careful about our terminology.

Many strength coaches say that sports-specific training does not exist. Yes and no. Duplicating a technical movement in a sport exactly with resistance may do more harm than good by affecting the timing of the sporting movement. Examples include throwing a weighted football (which can be pretty harsh on the shoulders) or swinging a weighted tennis racket.

A house needs to be built on a solid foundation, and likewise, a thrower must have a stable foundation from which to produce rotational force. Let’s begin with some definitions, says Kim Goss. Share on X

A better approach is to practice movements similar to an athlete’s movements in sports but not exactly specific. The popular term for these exercises is “special strength” training. Pushing or pulling a sled could be considered special strength training for a sprinter. Dr. Yuri Verkoshansky, a Russian jump coach, and his Russian colleague Bondarchuk have written extensively about special strength training. Bondarchuk, for example, looked at the correlation between the squat and throwing ability of elite hammer throwers.

Bondarchuk found that the “correlation coefficient” between the squat and hammer throw decreased as athletes achieved higher levels of throwing ability. For the 60-65m throwers, the squat correlation was .437 but decreased to .196 for athletes throwing 75-80m. In contrast, the 10-kilo hammer correlation went from .542 for the 60-65m throwers to .824 for the 75-80m throwers. The takeaway is that after developing a foundation of power with weightlifting movements, throwers often add “special strength” exercises that strengthen rotational strength and power.

When determining which special strength exercises to perform, consider the anatomy of the oblique abdominal muscles. These muscles are called oblique because of their position relative to the spine; they are oblique to the spine. Further, most oblique fibers are arranged and positioned diagonally rather than transversely (perpendicular) to the spine (Image 7). According to Gagné, this diagonal alignment makes the obliques ineffective in producing force horizontally.

“The gastrocnemius has fibers arranged longitudinally,” says Gagné. “You would not work the calves by pulling your legs across your body, rather, use an exercise such as a standing calf raise to apply resistance longitudinally. Likewise, you should not train your obliques by rotating your spine horizontally on a single axis, such as with the torso machines you find in many commercial gyms. This horizontal movement is not natural and creates large shearing forces on the spine, particularly when seated.”

Image 7. The oblique muscles run diagonally rather than transversely (perpendicular) to the spine (Image via Wikipedia Commons. Source. Creative Commons License here).

“Because the oblique fibers are aligned diagonally to the spine, they are best suited to produce positive and negative torsion,” says Gagné. “Negative torsion is rotation coupled with extension, such as when a thrower releases the discus. Positive torsion is rotation coupled with flexion, such as when a golfer brings their club down to hit the ball.” Image 8 shows two woodchop exercises performed with a cable machine that creates positive and negative torsion.

There are many ways to produce special rotational strength, including cables, flywheel devices, medicine balls, and kettlebells (as the handles allow for easy release). John Powell supplemented his discus training by throwing the hammer, which could be considered a form of special strength training. (Fun Fact: Powell’s strength coach was Richard Marks, a shot putter with a best of 62-27 (18.98m). I saw Marks snatch 363 pounds in a local meet in 1976 when the American record was about 380.)

When it comes to program design, counter-rotation must be considered. Neuroscientist J. P. Roll found that strengthening one side of the body will neurologically “code” the strength training effect of the other side. Further, the ability to produce rotation in one direction is influenced by how well that individual can produce rotation in the opposite direction.

“In working with professional golfers, we found we can increase the ability of a right-handed golfer to generate club speed by having them work with a left-handed club,” notes Gagné. I’ve also heard about one former world record holder in the javelin, Tom Petranoff, who occasionally threw with the opposite arm to prevent injuries.

Besides special strength exercises, Gagné says the overhead squat is an excellent exercise for developing rotation because it involves considerable counter-rotation to maintain proper alignment. Further, the exercise can determine if an imbalance is present. Canadian strength coach Charles Poliquin often used the overhead squat to assess his athletes and taught it in seminars. The assessment was also used in a corrective exercise class I took while working on my master’s degree at A.T. Still University.

There are many variables associated with achieving the highest results in throwers. Yes, elite shot putters, hammer throwers, and discus throwers tend to be significantly taller and larger than other track and field athletes, but much bigger is not always much better. Also, rather than training harder, the focus should be on training smarter with dynamic exercises that develop explosiveness and special strength exercises that target the muscles that produce rotation. It’s a question of balance.

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References

Davis, Dave. “Move Over World…Here Comes Brian Oldfield.” Strength and Health. May 1973.

Glenda Ford, Pioneer Athletics Hall of Fame.

Goss, Kim. “Suzy Powell: A Date with Destiny.” BFS magazine. Summer 2000.

Dangel, Donald R; Dengel, Olivia H. “Body Composition—Methods and Importance for Performance and Health.” Techniques Magazine. Reprinted July 7, 2016, in coachesinsider.com.

Garhammer, John. “A Review of Power Output Studies of Olympic and Powerlifting: Methodology, Performance Predication, and Evaluation Tests. Journal of Strength and Conditioning Research. 1993, 7(2): 76-89.

Charniga, Andrew, Jr. “Scaling of Body Mass in Weightlifting: What Can Happen to the World’s Strongest Weightlifters.” Sportivnypress.com. June 18, 2018.

Abramovsky, Igor. “A Weightlifter’s Excess Bodyweight and Sport Results.” Sportivnypress.com, Bud Charniga Translation: May 2, 2014 (Originally published in 2002).

Meranzov, C; Spasov, Sinclair; et al. “Trends in the evolution of sports results during the 1973 -1983 period,” IWF Coaching – Refereeing – Medical Symposium, Bad Blakenburg (GDR). May 28 – 30:1985:29-34.

Caughey, RM, and Thomas C. “Variables Associated with High School Shot Put Performance.” International Journal of Exercise Science. October 1, 2022: 15(6):1357-1365.

Nuckols, Greg. “Sarcoplasmic Hypertropy: The Bros Were Probably Right.” Stronger by Science. ND

Scottish Athletics. “Lessons From Bondarchuk.” HMMR Media. September 2017.

Florence, Mal. “Brenner to Miss Olympics Again After Tearing Tendon.” Los Angeles Times, June 21, 1988.

Bondarchuk, Anatoliy P. Transfer of Training in Sports. Ultimate Athlete Concepts. 2007: 97-125.

Gagné, Paul, Personal Conversation, September 6, 2024.

Goss, Kim. “Adam Nelson, The Giant Killer.” BFS magazine. Summer 2004.

“Javelin Throwers Weak Side Training Logic.” Javelin Throw Magazine.

Chapman J, Henneberg M. “Switching the handedness of adults: Results of 10 weeks training of the non-preferred hand.” Perspectives in Human Biology. 1999; 4 (1), 211–217.