This is the first NFL-225 study to used a large sample of top-level college players to assess the accuracy of predicting 1RM bench press from repetitions completed using an absolute load of 102.3 kg (225 lb). The prediction equation produced in this study was similar to others developed on players at various levels of competition, indicating a consistency in the relationship between maximum repetitions with submaximal loads and peak strength. Four of the previous NFL-225 equations developed on less elite players predicted over 60% of the sample within ±4.5 kg, with most of the agreement coming when 10 or fewer repetitions were completed. Cross-validation of the newly developed equation on a random sample of elite players predicted 67% within ±4.5 kg of their actual 1RM. Prediction accuracy tended to be greater in players completing ≤10 repetitions, which agreed with previous studies (1,3,6,9,10,15). This is also the first study to indicate that mid-range body weights (88–99 kg) tended to have their 1RM predicted with greater accuracy than did lighter or heavier players.
Several studies have suggested that including various anthropometric dimensions would reduce the error associated with predicting the 1RM from NFL-225 repetitions alone (3,18). Whisenant et al. (18) used a small number (n = 69) of Division IAA players, whereas Hetzler et al. (3) used Division I players (n = 87). Each study indicated different anthropometric variables contributed to increased amount of variance accounted for, making it difficult to decide exactly which dimensions were better suited to reducing the prediction error. Furthermore, neither study provided a detailed analysis of how much the prediction error was reduced nor if the reductions were uniform across players of all sizes. Using height and weight on the current sample to estimate FFW (4) allowed the determination of 1RM from the equation of Whisenant et al. (18) but produced only 52% of the current sample with estimates within ±4.5 kg of their actual 1RM. This was substantially less when only the NFL-225 repetitions were used. Furthermore, the positive correlation (r = 0.20) between body mass and the difference between the Whisenant et al. (18) predicted 1RM and actual 1RM indicated a heterogeneity in the distribution of the values, with larger individuals having greater error.
The current study exhibited the same problem as previously noted in all the other studies using an absolute load to estimate 1RM: progressively greater prediction error as the number of repetitions increased beyond 10. In the cross-validation group, the new equation produced 86% of players performing ≤10 repetitions with prediction errors of ≤4.5 kg, which dropped to 61% for players completing 11 to 19 repetitions and 47% for players completing ≥20 repetitions. Among the 4 body weight classifications, the lighter 2 groups produced more of the sample (73%) with ≤4.5 kg error than the heavier 2 groups (59%). Applying various combinations of simple anthropometric variables such as height, weight, and BMI did not alter the prediction accuracy in any of the weight groups.
In conclusion, it would seem that the use of NFL-225 repetitions to estimate 1RM bench strength has statistical support at all levels of college football. The current equation on elite Division I players follows the same trends as the previous research indicating that individuals performing fewer repetitions (≤10) seem to have better prediction accuracy than players performing more than 20 repetitions. Because the objective of the NFL-225 test is not necessarily to estimate maximal strength among professional candidates, there is little likelihood of the test being changed in the foreseeable future to a more equitable predictor for all size players. Previous pilot work has suggested that perhaps a weight equivalent to 110% of a player's body weight would provide a better repetition range for estimating 1RM (13). However, such a suggestion would have to be validated on elite players at the Division I level. The performance on the NFL-225 test, for both drafted and free-agent players in the professional ranks, is one of the important criteria contributing to being selected for and remaining with a professional team (14,16).
The findings of this study suggest that the NFL-225 test may be an acceptable approach to estimating 1RM bench press strength in Division I college football players. Although the 1RM determination is considered safe in most cases (11), injuries have occurred which could hamper training and playing time for significant players (2,12). Although injuries can occur when attempting maximal repetitions with submaximal loads, emphasis on proper form and maintenance of careful spotting could make the NFL-225 test a quick and safe method of assessing upper-body strength in elite players.
The new equation presented in this study should estimate a large proportion of a Division I team with an error of <5%. Because of the heteroscedasticity that occurs at the upper end of the repetition continuum, the prediction error may increase from 6 to 12% where players perform more than 20 repetitions. Of the players performing more than 20 repetitions, only a small proportion was underpredicted (16%) or overpredicted (16%) by more than 6%. Those players who were underpredicted had a significantly higher bench press per kilogram values than those who were overpredicted. This fact may aid strength and conditioning specialists in making better application of predicted 1RM performance for establishing periodized resistance programs throughout the year.
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