Mixed martial arts (MMA) cage fighting has continued to increase in popularity considerably since the debut promotion of the Ultimate Fighting Championship (UFC) in 1993 in the United States of America (11). Mixed martial arts refers to the study of multiple martial arts to prepare an athlete for all scenarios of a fight, including stand-up fighting at a distance, stand-up wrestling, and ground wrestling. During its initial years, the UFC implemented many new rules to meet requirements of different athletic government bodies in the United States to allow for further growth of the sport. One of the rule changes introduced was the weight-class system that was implemented to create more equity in terms of size and strength for the athletes participating in the sport (23). In both amateur and professional MMA events, an official weigh-in is held approximately 24 hours before the competition, which aims to confirm the athletes' registered weight class. Because of this procedure, a highly periodized and regimented practice referred to as weight cutting has become a prolific aspect of MMA competition across all levels of competition, with a recent study by Barley et al. (7) reporting that 95% of MMA athletes had specifically lost body mass (BM) to compete.
Weight cutting is a purposeful and tactical yet drastic approach commonly used among all combat sports (7) that is independent of any weight fluctuations resulting from higher training load, whereby athletes train at a heavier BM, then engage in one or several methods to induce rapid BM loss including drastic caloric restriction (34), water loading (33), sweating methods via either or both passive and active dehydration (21), and use of laxatives or diuretics (20). In MMA, this commences after the completion of a formal “training camp,” typically 7 days before their scheduled weigh-in and is consistent for both amateur and professional athletes. The intention of this method is to qualify for a lower weight class and then rapidly regain as much BM as possible in the 24 hours between weigh-in and the fight so that they compete at a heavier weight than their weight class (8). Presumably, this gain in BM confers an advantage if other variables such as acceleration remain constant for (e.g., striking) force to be larger/stronger. Thus, athletes and trainers alike erroneously believe that if their opponent either does not engage in weight cutting, cuts less BM, or regains less BM after weigh-in, the athlete who has cut the most BM to meet the designated weight class should have greater force-producing capabilities and be harder to manipulate with wrestling, thus having more powerful impacts due to a weight advantage during the bout (5,8).
The theory that weight cutting might provide a competitive advantage in combat sports was supported by the findings of Wroble and Moxley (40), who demonstrated that 57% of wrestlers (159 varsity wrestlers) cutting >5% BM placed in the top 4 of a tournament, whereas only 33% of the wrestlers who lost <5% total BM placed in the top 4. Similarly, Alderman et al. (1) reported that wrestlers who gained greater magnitudes of BM (mean 3.78 kg; approximately 5% BM) after weigh-in were more successful in terms of fight outcome compared with those who regained less (mean 3.05 kg; approximately 4% BM). However, it has been shown that MMA athletes (19,26,31) consistently cut more BM than athletes in other combat sports such as wrestling (40), Judo (3), Jiu Jitsu (10), and boxing (36), but it is not yet known whether the competition outcome in MMA is influenced by the higher magnitudes of BM loss that has been observed in these athletes.
Given that the primary mechanism of weight cutting is a rapid reduction of body fluid that results in hypohydration (12,31), especially for MMA athletes (7), it is prudent to consider the possibility that cutting larger magnitudes of BM may actually be detrimental to physical, physiological, and cognitive performance, thus potentially contributing to less desirable fight outcomes (i.e., loss). For example, Barley et al. (6) recently investigated several physical performance markers before and after 5% BM reduction through active dehydration and heat exposure in 14 MMA athletes and reported significant reductions in medicine ball throw distance and sled push performance even after 24 hours of recovery. This suggests that the 24-hour recovery period between weigh-in and the commencement of the fight may not entirely mitigate the residual effects of dehydration and weight cutting on some aspects of physical performance.
The purpose of this study was to identify whether fight outcome (win vs. loss vs. type of loss) was influenced by magnitudes of BM lost through weight cutting and BM regained after official weigh-in in both amateur and professional MMA athletes with previous weight-cutting experience. It was hypothesized that athletes who lose their fights would cut more BM than athletes who win their fights, and more broadly, that greater reductions in BM would result in a greater likelihood of losing a fight. We further hypothesized that athletes would fail to recover the full magnitude of BM lost through weight cutting during recovery between the weigh-in and the fight and that recovery would not influence the competition outcome.
Experimental Approach to the Problem
Body mass data were collected from 75 active MMA fighters (59 amateur and 16 professional) before commencing weight-cutting practices which was self-reported 7 days before the official weigh-in of each event (immediately after their formal training camp), at their official weigh-in (reported by the regulating body), and by the primary researcher immediately before competition. The research experiment was descriptive in nature.
Seventy-five MMA fighters (73 men and 2 women) who had previous weight-cutting experience and who were planning to engage in weight-cutting practices for an upcoming fight were recruited for this study. The sample consisted of 6 light–heavyweight, 2 middleweight, 11 welterweight, 21 lightweight, 18 featherweight, 3 bantamweight, and 14 flyweight athletes. Screening occurred indirectly through gaining eligibility to fight in their respective promotions; thus, all subjects were aged 18 years and older and deemed physically well by the New South Wales (NSW), Australia, Combat Sports Authority and registered medical professionals before competing. The fighters competed at the amateur or professional level at MMA promotions hosted in NSW between the 10th of March and 12th of August, 2017. Promoters and event organizers were contacted through email upon release of their event and provided details of the study, including the subject information sheet and written informed consent form. The email sought permission for their promotion to be included in the study for the purposes of recruiting subjects. Of the 10 promoters contacted, 3 approved their events to be involved; thus, data were collected at Superfight 4 (Punchbowl, NSW), West Region Fight Night 3 (Lithgow, NSW), Urban Fight Night 11 (Liverpool, NSW), and Urban Fight Night 12 (Liverpool, NSW). With the promoter's support, the study was then advertised to MMA athletes fighting within those promotions. After thorough explanation of the study whereby the benefits and risks were explained, and being provided with the subject information sheet, all subjects signed a letter of written informed consent. No subjects were younger than 18 years, and therefore, no parent/guardian consent was required. Subject characteristics were measured standard deviation. This project was approved by the Charles Sturt University Faculty of Science Low Risk Ethics Board (approval number 400/2017/05), in accordance with the Declaration of Helsinki.
All research subjects resided in Australia, but many were required to travel to NSW for their fight from interstate. For this reason, subjects were asked to self-report their precut BM (i.e., their BM before commencing any method of weight-cutting practices), which is colloquially known as “walking weight” in the MMA community. Subjects were asked to provide their “walking weight” attained in the morning (nude, after eliminating first urine, and before eating or drinking) 7 days before their scheduled weigh-in. Athletes were officially weighed-in by the Martial Arts Sports Association (MASA) 24 hours before their fight. The raw magnitude of BM lost due to weight-cutting practices was derived by subtracting the official BM from the “walking weight.” Immediately before their fight, athletes were asked to step onto a set of scales (iHealth Scale Model: HS3; iHealth Lab Inc., Mountain View, CA) to ascertain their “recovered BM,” which was the magnitude of BM regained after their official weigh-in on the previous day. All data collected were anonymized before data entry.
Data were analyzed according to the following fight outcomes: (a) win; (b) loss by technical knockout (TKO) or KO; (c) loss by submission; or (d) loss by the judge's decision. Technical knockout and KO outcomes were combined because of low frequencies for KO outcome. This is to be expected in MMA competition because referees, ringside physicians, or their team members will generally stop the fight when the athlete is deemed unable to defend themselves or they have sustained a serious injury, thus ending in TKO. Within our data set, one fight was stopped by the fighter's corner coaching team because of significant injury, and they believed that if the fight had continued, it would have resulted in a KO; therefore, this result was recorded as loss via TKO. The following formula was used to calculate the percentage of BM lost:
To determine the percentage of BM regained after official weigh-ins, the following formula was calculated:
All data were screened for normality using Shapiro-Wilk tests, and the Levene test was used to determine homogeneity of variances. No homogeneity violations were detected for magnitude of BM cut at baseline (precut), weigh-in (postcut), or prefight, and all data were found to be normally distributed. A 2-way analysis of variance (ANOVA) (time × outcome) was used to determine the main effects of time and outcome on magnitude of BM lost, and time versus fight outcome interactions, where fight outcome was grouped either as win versus lose or win versus type of loss. Mauchly's test statistic was used to determine the sphericity of the data. If the condition of sphericity was not met (p ≤ 0.05), the degrees of freedom were adjusted based on the extent of the violation. If the Greenhouse-Geisser estimate of sphericity (ε) was >0.75, the Huynh-Feldt correction was used, but if ε was ≤0.75, the Greenhouse-Geisser correction was used. Where a significant time, fight outcome, or outcome-by-time interaction was observed in the repeated-measures ANOVA, a 1-way ANOVA was performed to compare mean differences (% change) in BM from baseline to weigh-in (% BM cut) and from weigh-in to prefight (% BM recovered) between groups for post hoc analyses. In addition, a logistic regression was performed to ascertain the effects of percentage BM cut on fight outcome. If effect sizes were required to aid the interpretation of tests of significance, Cohen's d conventions were set at small (0.2), moderate (0.5), or large (0.8) (18). Statistical analyses were performed using SPSS software for MS-Windows version 20.0 (statistical package for the Social Sciences, Chicago, IL). For all comparisons, p ≤ 0.05 was regarded as significant. Data are presented as means ± SD.
Thirty-eight subjects won, and 37 lost their respective bouts with 17 subjects losing by KO/TKO, 12 by the judge's decision, and 8 by submission. Mean ± SD BM results are shown in Table 1. The 2-way ANOVA showed no main effect for outcome (F1,73 = 0.583; p = 0.447), but there was a significant main effect for time (F1.66,121.33 = 187.05; p < 0.001) and a significant outcome-by-time interaction when outcome was split into win vs. lose (F1.66,121.33 = 3.56; p = 0.04). Post hoc analyses on percentage differences revealed that athletes lost a significant amount of BM between baseline and weigh-in (p < 0.001, d = 0.72, 95% confidence interval [CI] = 0.38–1.04) and that athletes who won their fight cut less BM (8.6%) compared with those who lost their fight (10.6%) (p = 0.04, d = 0.48, 95% CI = 0.02–0.93; Figure 1). However, when the analyses were repeated to determine the effects of type of loss, there were no significant differences between groups (all p > 0.05). Furthermore, athletes recovered a significant amount of BM between weigh-in and prefight (p < 0.001, d = 0.50, 95% CI = 0.17–0.82). However, there were no significant differences in recovered BM between athletes who won (6.8%) vs. lost (7.4%), or type of loss (all p > 0.05; Figure 2). A logistic regression was performed to ascertain the effect that the percentage of BM cut had on the likelihood that subjects would lose their fight. Percent BM cut significantly predicated the outcome (B = −0.12, p = 0.048). The odds ratio was 0.89 indicating that for every 1 unit of BM cut, the odds of reporting a win decrease by 11% (95% CI: 0.79–1.00).
Table 1 -
Mean BM (kg) and SD
for all fight outcomes at baseline, weigh-in, and prefight time points.*
||75.23 ± 9.81
||78.22 ± 12.34
||78.18 ± 11.26
||77.63 ± 12.21
||78.67 ± 14.79
||68.81 ± 9.61
||69.73 ± 9.64
||70.05 ± 8.66
||68.24 ± 11.56
||70.27 ± 10.39
||73.39 ± 9.49
||74.86 ± 10.40
||74.90 ± 9.67
||72.69 ± 11.05
||76.25 ± 11.62
*BM = body mass; KO = knockout; TKO = technical knockout.
This study aimed to investigate the effects of weight-cutting practices on competition outcome in MMA. The primary finding of this study was that cutting greater amounts of BM was significantly correlated with losing the fight and that athletes who lost their fights cut significantly more BM compared with those who won (10.6 and 8.6%, respectively). There were no differences between the type of loss (KO/TKO, submission, and decision), and no significant differences were observed between groups in the magnitude of BM recovered, either expressed as a percentage of precut BM or as a percentage of BM lost during weight cutting. These results indicate for the first time that the magnitude of BM lost during weight cutting can be detrimental to the outcome of an MMA fight, with those losing more BM more likely to lose their fight.
It has previously been reported that MMA athletes tend to cut significantly more weight than that observed in other combat sports (1,4,10,32), and our findings add to that body of evidence. For example, a recent study by Matthews and Nicholas (31) reported 8% reductions in BM in MMA athletes, and Barley et al. (7) reported losses ≥12% in MMA athletes within their samples, which is comparable with the magnitudes observed in our study. However, Judo, Jiu Jitsu, Karate, boxing, and Taekwondo commonly see cuts of 2–6% (4,7,10,36). One potential reason for the greater cuts in BM observed in MMA compared with other combat sports is the duration of time between weigh-in and competition in MMA. That is, other combat sports perform their weigh-ins closer to the competition, Barley et al. (7) reporting the weigh-in to fight interval as an average of 6 hours for Brazilian Jiu Jitsu, 7 hours for boxing and wrestling, 11 hours for Judo, 18 hours for Muay Thai/kickboxing, and 19 hours for Taekwondo, whereas 24 hours for MMA. The result of the longer recovery period after weigh-in for MMA is that there is more time to rapidly regain BM; thus, greater magnitudes of BM are cut through more drastic weight-cutting methods.
Regarding the effects of weight cutting on the competition outcome, our results are in contrast to those reported in similar studies conducted in American wrestling (1,40). These studies concluded that higher magnitudes of BM cut were associated with greater success in wrestling competitions, whereas we showed that greater magnitudes of BM cut were associated with losing the fight. There are several possible explanations for this. First, there is a higher frequency of striking techniques used in MMA that may increase the physiological demand on athletes due to increased stress associated with receiving strikes from the opponent and the added demands from different movement patterns associated with striking (25,30,39). Second, the total magnitudes of BM cut in these studies were approximately 5%, which is substantially less than the 8.6 and 10.6% (winners and losers) of BM observed in this study. Therefore, the greater magnitudes of BM lost by MMA athletes would likely result in significant dehydration-related impairments in anaerobic performance (6,27,41), aerobic performance (14,15,21,28), reaction time (22,38), or cognitive impairments (16,29,38,41). Severe dehydration may influence these various aspects of performance through several mechanisms, such as reduced muscle fiber contractility from compromised sodium levels (2), increased rate of central or peripheral fatigue development (9), reduced efficiency of blood flow due to compromised blood plasma volume (13), and negative effects on cognitive function via negative mood state changes (17). Even at moderate levels of BM reduction (4.8%), Barley et al. (6) demonstrated impaired performance in a repeat sled push, medicine ball chest throw, and vertical jump in MMA athletes compared with a control condition after a 24-hour recovery. In addition, Hickner et al. (24) found significant reductions in performance of repeated maximal arm crank efforts after 4.5% BM reduction, with the effects greatest during the later bouts. This suggests a compromised ability of aerobic metabolism to sustain repeated maximal efforts (24). It should be noted that most studies investigating the effects of dehydration usually only induce up to 5% reduction in BM; thus, the performance detriments in MMA fighters losing ≥10% of BM are likely to be drastically exacerbated.
The results of the current study further showed significant BM recovery (6.8 and 7.4% in those who won and lost, respectively) from weigh-in to before competition, but this did not mitigate the negative effects of cutting greater magnitudes of BM. That is, the amount of BM recovered did not significantly alter the competition outcome in this study. Two previous articles have reported recovered BM in MMA athletes from after weigh-in and before competition. Matthews and Nicholas (31) observed a mean BM recovery of 11.7% in a 32-hour recovery period, whereas Jetton et al. (26) observed a mean BM recovery of 4.4% in a 22-hour recovery period. The larger results observed in the current study may be attributed to the fact that BM lost due to weight-cutting practices was not reported by Jetton et al. (26). It is likely, however, that subjects of this study reduced more BM. By contrast, our study showed smaller recovered BM magnitudes compared with Matthews and Nicholas (31), which is most likely due to the longer recovery period observed in their study (32 hours compared with 24 hours in our study).
This study has several limitations that should be considered when interpreting these results. Most notably is that baseline BM was self-reported by athletes. However, qualifying for a fight in MMA is explicitly linked to very tight BM ranges (weight-class classifications) with serious consequences for not making their registered weight class. As a result, athletes and coaching staff are meticulous with BM management during competition periods, particularly at the completion of the periodized training camp 7 days before weighing in, and there was nothing to be gained nor lost for these athletes by reporting misleading data. As such, the researchers concluded that some of the innate reliability concerns associated with self-reporting data by a lay-person were likely to be mitigated. Furthermore, this study was strictly concerned with the “acute” phase of weight cutting that typically takes place approximately 7 days before an official weigh-in; however, the previous literature has identified that combat sports athletes also incorporate gradual weight-loss strategies that may reduce BM before the 7-day time frame that was utilized for this study. A second important limitation of this study was that both amateur and professional athletes were included, despite only including subjects who had previous experience with weight cutting. This approach was taken because it is most closely aligned to the specific research questions and allowed the recruitment of an adequately sized sample to ensure that the study was sufficiently robust to avoid type I or type II error. Although it was not the purpose of the study to delineate between levels of competition, it is acknowledged that further research to investigate the effects of fighting experience would benefit the combat sport community. Finally, the specific methods of weight cutting used by subjects in this study were not recorded or controlled, and hydration status was not objectively evaluated, as it was beyond the scope of the current project. Future research on the differential effects of various methods of weight cutting and specific hydration status would add value to the current body of evidence.
The results of the current study, in combination with findings from the previous literature, provide a strong rationale for instigating change in current weight-cutting procedures for MMA athletes. First, although drastic weight cutting with extreme measures is not in the best interest of athlete safety, it is evident that this practice is detrimental to the physical and physiological performance of these athletes, with greater weight cutting appearing to result in a greater likelihood of losing the fight. Mixed martial arts authorities could consider reviewing their weigh-in procedures to either scaffold the weigh-in leading up to the fight, or do it closer to the commencement of the fight, such as the same-day weigh-in used by the National Collegiate Wrestling Association, whereby athletes are required to weigh-in on the same day of the competition (35). This would likely be effective in mitigating larger magnitudes of BM cut by MMA fighters. We suggest that if actions such as these were taken, athlete performance may be improved, and the risks of health implications associated with drastic weight fluctuations might be mitigated.
There were no additional funding sources or professional relationships to disclose relating to this study. Results of this study do not constitute endorsement of the product by the authors or the NSCA.
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