The punch is a key component of boxing and various combat sports. It is used to inflict physical damage, develop tactical advantage, and score points against an opponent (25). Punching is a complex motion that involves movement of the arm, trunk, and legs (29), but the lower body is considered a primary contributor to an effective punch (8). Although speed and accuracy are needed for a punch to be effective (22), several studies have shown that punching force is paramount to a fighter’s victory (21,25). Research into punching has focused primarily on observing forces, with only one study of note focusing on potential training strategies for improving punching force (29). Using research into the lower limb’s involvement in punching and other similar movements, this review will examine the assessment of punching forces and will further explore potential strength and conditioning strategies for improving punching force.
The databases Google Scholar, Pro Quest, and SportDiscus were explored for relevant research with the truncated keywords “punch” and “strike” and combined with “sport,” “combat sport,” and “force.” Of the 43 articles found, only those measuring punching forces or ground reaction forces (GRF) (n = 13) were included in this review. Most of these studies focused on the so-called “straight rear hand” punch, also known as the “cross.”
MEASUREMENT AND ANALYSIS OF PUNCHING FORCES
Punching forces can be measured and analyzed to provide diagnostic information for programming and prognostic information for talent identification and team selection. As one of the key indicators of performance, monitoring changes in punching force can be used as a diagnostic tool for the design and efficacy of strength and conditioning interventions. Furthermore, the measurement and analysis of punching forces can be used as a prognostic tool for categorizing combat sport athletes according to their punching forces for a potential aid in team or program selection. Combat sports are in a unique position, lacking this important monitoring tool in common practice.
Throughout the literature, a variety of devices have been used to monitor punching forces. Although several unique designs have been used, such as pressure transducer submerged in water-filled heavy bag (9), and load cells in the neck of a dummy (31), the most common design used to record punching forces is piezoelectric force transducers embedded in a target (Table 1) (3,10,26). The preferential choice of using piezoelectric force transducers could be because of their accuracy, ease, and proven reliability (coefficient of variation = 1.8%–3.6%) (12). The piezoelectric force transducers have been used to explore injury and health issues in boxers (3,31) and to correctly identify boxer’s experience levels through their punching forces (26).
In a distinctive study design, Pierce et al. (21) measured punching force from the fist of the fighter rather than from the target of a punch. Using the Bestshot system, Pierce et al. (21) were able to have a force sensor placed inside of the gloves of boxers and have the resulting impacts transmitted via radio frequency telemetry to a computer during 6 professional boxing matches across multiple weight classes. This advancement in technology allowed for a flexibility of punch selection and, more importantly, the ability to record actual fight data. In addition, the system was found to be reliable and comparable with the mounted triaxial piezoelectric force transducers used by Smith et al. (26). A key finding by Pierce et al. (21) was that peak and mean force outputs in the ring were substantially lower than those assessed in the laboratory. The authors note that the hardest punch recorded by a heavy weight boxer registered 3,554 N of peak force. This result was substantially lower than the 4,800 N ± 227 found by Smith et al. (26) and the result of Atha et al. (3) 4,096 N. This discrepancy raises a potentially important issue. Laboratory and competition punching assessments may differ because of the dynamic nature of combat sports and as such should be further investigated to find if a direct relationship exists. Whether laboratory based or field based, the current systems used to monitor punching forces report validity and reliability and give the modern strength and conditioning practitioner an array of tools to quantify punching forces. Of additional interest is that Pierce et al. (21) found that when a fight went to the judge’s scorecards, the victor was, without fail, the athlete who had landed the greatest total force to his/her opponent. This result identifies the potential benefit of mean and peak punch force development by strength and conditioning practitioners.
CONTRIBUTORS TO PUNCHING FORCE
The rear hand punch can effectively be broken into 3 primary contributors to punching force: (a) the contribution from the arm musculature into the target, (b) the rotation of the trunk, and (c) the drive off the ground by the legs (8). Filimonov et al. (8) analyzed 120 boxers of varying ability and found that boxers with more experience had a greater contribution from their legs to the punch when compared with the other contributors (i.e., arms and trunk). Using biomechanical observation and force dynamometry, Filimonov et al. (8) found that in experienced boxers, the legs contributed 38.6% of total punching force compared with 32.2% for the intermediate and 16.5% for the novice boxers. Smith et al. (26) assessed elite, intermediate, and novice boxers with a wall-mounted force plate and found that experience linked to greater punching force. Elite boxers produced 4,800 ± 227 N in peak force during the rear hand punching, whereas intermediate and novice boxers produced 3,722 ± 133 and 2,381 ± 116 N, respectively. The findings of the 2 previous studies suggest that the greater the contribution from the legs to the punch, the greater the force. In support of such a contention, Filimonov et al. (8) grouped the subjects by their stylistic preference as “knockout artists,” “players,” and “speedsters.” The study found that knockout artists had leg drive contribution that was higher (38.6%) than the subjects grouped as players (32.8%) or speedsters (32.5%) who relied more on a contribution from trunk rotation.
In contrast with the results of Filimonov et al. (8), Mack et al. (16) found a greater relationship of punching forces in 42 amateur boxers to preimpact hand velocity (R2 = 0.39 and 0.38) rather than to the forces generated by the athletes’ legs (R2 = 0.10 and 0.10). The authors assessed the contribution from the legs via a “unique” FAB system (FAB goes undefined), which estimated force from the dominant leg during the punches. A potentially more valid and reliable measure of leg GRF would be a measurement from a force plate (9), which could be combined with a motion capture system to further explore the conclusions of Mack et al. (13). Comparison of preimpact hand velocity and leg drive may not be appropriate; leg drive most likely affects and develops preimpact hand velocity. In effect, what Mack et al. (16) explored in their study would be the same as comparing a baseball’s velocity preimpact with a pitcher’s lower body contribution during the windup. The lower body has already imparted its energy into the ball, so any comparison of the preimpact velocity of the ball is affected by that input (15). Likewise, the legs contribute to hand velocity during punching movements (29). An additional and potentially more relevant association to examine is leg drive with the preimpact hand velocity rather than punch forces on impact with preimpact hand velocities. In summary, there is a conflict in current research regarding the importance of leg drive to punching power that requires further exploration.
Investigating other sports, which follow roughly similar movement patterns, the importance of the contribution of the lower body is seen throughout the literature. An analysis by Terzis et al. (28) found that elite shot putters contributed roughly half of their throwing performance from the lower body. Exploring overhead throwing in children Stodden et al. (27) found an improvement in ball speed from 8.41 ± 5.45 to 14.20 ± 4.5 m/s with the inclusion of an ipsilateral step and a further improvement to 28.10 ± 1.6 m/s with a more punching specific (29) contralateral step. A study by Bouhlel et al. (6) found that in national level javelin throwers, performance correlated strongly with maximal anaerobic power per kilogram (R = 0.76, p < 0.01) and maximal velocity (R = 0.83, p < 0.001) produced by the legs during a force-velocity test. These findings indirectly support the conclusions by Filimonov et al. (8) about the importance of leg drive to develop punching forces.
POTENTIAL STRENGTH AND CONDITIONING STRATEGIES FOR IMPROVEMENT OF PUNCHING FORCE
No studies were found that explored in depth the impact of strength and conditioning practice on punching force. Hence, this review will examine boxing studies that have superficially addressed the issues and look at other sports that have explored the effects of strength and conditioning practices in greater depth. To achieve the goal of increasing leg drive during a punch, both Filimonov et al. (8) and Turner et al. (29) suggested the use of axial loaded movements such as squats, weightlifting variations (snatch, clean, jerk, etc.), and vertical jumps. Although the argument for axial loading appears sound, these movements only occur bilaterally and in the vertical direction. Leg drive during punching requires GRF to be developed in the vertical and horizontal directions, with various staggered stances. Depending on the primary direction of the GRF during punching, it may be more appropriate to emphasize longitudinal movements, such as sled pulling, jumps, and throws seen in Table 2.
An argument in favor of vertical GRF being the primary factor in the punch can be extrapolated from a study by Akutagawa and Kojima (1), exploring backhand shots of 14 male colligate tennis players. The authors found substantially greater vertical GRF than horizontal GRF in subjects as they hit tennis balls. This may be applicable to understand GRF during punching as part of the tennis player’s backhand technique used rotation of the pelvis in a similar manner to that found in many forms of punching.
In contrast, support for horizontal GRF as the primary factor in punching force is found in Cesari and Bertucco (7), who observed large changes in the center of pressure (COP) anteriorly/posteriorly as karatekas (karate practitioners) punched a target. The study also compared experienced with less experienced karatekas and found that with experience there was a greater COP movement anteriorly and less posteriorly. Although Cesari and Bertucco (7) focused their results on the karateka’s ability to maintain dynamic stability, this study still helps to illustrate the directionality of the force during a punch. Similarly, Gulledge and Dapena (11) found high levels of horizontal force in rear hand punches recorded on a force plate but unfortunately did not examine vertical forces. The strength of both studies was the inclusion of a force plate to assess the participants. If future research corroborates these findings, a strength and conditioning practitioner would be well served to focus on longitudinally loaded movements to complement the axial loaded movements suggested by Filimonov et al. (8) and Turner et al. (29).
A third theory in regard to the specificity of GRF in the punch may be proposed. There may be no singular GRF direction that is optimum for improved force production. As a movement that involves rotation of the pelvis, trunk, and shoulder (29), both vertical and horizontal force may contribute near equally to the punch in a rotary movement. Until further research exploring the directional application of leg drive is conducted, current strength and conditioning practitioners are reliant on an incomplete picture of punching and the components that affect it.
Using the literature reviewed in this article, basic strength and conditioning suggestions can be provided for the development of punching force in combat sports athletes. First and foremost, it is recommended that lower limb strength and power are considered for improving punching force, seen in Table 3. Although strength and power are also important for both the upper body and the core in a more general sense, this section will focus on specifics for improving punching force as currently understood from the literature. That is, the development of lower-body strength and power, core stability, and upper limb velocity. In regard to training the lower limbs for punching, there is currently a paucity of research exploring the specificity of GRF direction. It is the view of the authors to focus equally on axial loaded movements (e.g., squats) and longitudinally loaded movements (e.g., sled pulls).
Punching is an extremely dynamic motion that occurs over a very short period (3). To properly prepare an athlete for a combat sport, it is important to develop force and velocity capabilities with the ultimate goal of producing the greatest total power output (24). Although there are many methodologies to produce such adaptations in athletes via periodization, this review will use the framework of linear periodization (5) to communicate training suggestions. The utilization of linear periodization in this review is for communication rather than recommendation of training progressions.
Following basic linear periodization (5), development of a maximal strength base is necessary during the general preparation phase. For the development of punching force, it would be appropriate to use axial and longitudinal exercises, for example, the squat for the development of vertical GRF and heavy sled pulls to develop horizontal GRF. Once a maximal strength base has been developed, it is then appropriate to focus on a conversion to power during the specific preparation phase. Weightlifting movements (clean, snatch jerk, etc.) could be used to develop axial power and medicine ball or shot throws to develop longitudinal power. It is important to ensure that when training for strength and power, appropriate rep ranges, loads, and rest periods are used. Possibly most important for combat sport athletes with the goal of increasing maximal strength and power for GRF development is the need to rest 2–5 minutes between sets (4).
Rest periods are a focus, as there are numerous pieces of literature that recommend circuit training for the conditioning of combat sport athletes (2,23). This focus may lead to an inappropriate emphasis on low rest resistance training despite the authors’ intent to inform conditioning practice not maximal strength training practice. A lower rest period between exercises will result in greater fatigue and consequently lower load use. When the goal of a strength and conditioning professional is to improve maximal GRF, longer rests are needed to allow for bioenergetic restoration and thus true maximal efforts (4), resulting in a neuromuscular stimulus rather than a metabolic. These recommendations are seen in full in Table 3. When training for the precompetition phase, the focus of a strength and conditioning professional should be on continued improvement of power but in a sport-specific context. For combat sport athletes, this could be accomplished through single or combination punches thrown on a bag or pad with rest periods used for the development of power (14). This recommendation again stands in contrast to commonly given advice for combat sports athletes regarding bag or pad work, as it is primarily used as a conditioning tool and not a tool for the improvement of strength and power. Additionally, the punch training for strength and power could be used along with near-maximal strength movements to take advantage of post activation potentiation and further improve punching force.
Regarding core training for punching, it is the recommendation of the authors to focus on lumbar stability training in relation to the rotational forces in the punch. An emphasis on lumbar rotational stability, rather than movement, is indicated to allow for a transmission of GRF through the lower body and into the upper body before making contact with an opponent (13,18). A stretch-shortening cycle (SSC) has been observed during punching (29) and other similar movements (30). By stiffening the lumbar spine through stabilization movements like those suggested, an improvement in trunk SSC could occur similarly to that seen in joint stiffness after resistance and plyometric training (19). Additionally, if mobility is overemphasized rather than stability, then the potential of injury is also increased because of movement in the lumbar spine (17,20), along with a potential reduction in punching forces. Differing from the lower-body progression of exercises, it is recommended that core exercise progresses in difficulty to stabilize rather than a maximal strength to power paradigm. Moving from floor-based movements like the prone quadruped to kneeling exercises like the split stance cable row and finally standing exercises like the pallof press. As the purpose of these exercises is to stabilize throughout the entirety of a bout, training stimulus should be focused on developing endurance to improve the fatigue resistance of musculature and enable it to resist the potentially high forces produced by the lower body.
Finally and indicated by the literature as of least importance for improving punching force is upper-body training. Current recommendations from Turner et al. (29) suggest a focus on ballistic training to increase the velocity of strikes. As little literature has explored punching in relation to the upper body and there is little relevant data that can be looked to from other sports, baseball pitching is too dissimilar and track and field sports use implements that have too great of mass, the recommendations from Turner et al. (29), included in Table 4, would be the most appropriate to implement with the current knowledge base.
These suggestions, although basic, do serve to produce a framework onto which a strength and conditioning professional can further explore the development of punching force.
Research into punching has illuminated various potential key performance contributors but has yet to examine fully their impact on punching performance. Similarly, GRF studies have explored multiple sports but have only assessed punching superficially. Advancements in the understanding of one or both of these areas could greatly improve strength and conditioning practices for punching performance. Current technology is capable of assessing punching force and allows for research into punch contributors and GRF to occur easily. As such, the stage is set for the first of potentially many studies to truly develop an understanding of punching and how to best train athletes to improve punching forces.
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