| Purpose: One repetition maximum(1RM)is the maximum weight that can be lifted only once in a given exercise using the correct technique.It is considered the most valid indicator of an individual’s dynamic strength and can be used as a reference for training intensity in strength training programs.Although traditional methods of measuring 1RM can accurately obtain an individual’s 1RM,they suffer from cumbersome and time-consuming protocols,rapid changes in 1RM,and,in particular,high risk of injury.The purpose of this study was to investigate and compare the validity of the load-velocity relationships to predict 1RM in free weight and Smith machine squats,to provide some scientific basis for athletes and coaches for the selection of the weight method to predict 1RM in squat,and to provide a reasonable theoretical reference for the application of monitoring and prescribed loading in strength training programs.Methods: Seventeen male collegiate athletes with strength training experience(age:21.7±1.8yrs,height:181.3±6.0cm,weight: 76.3±11.2kg,training experience :5.6±2.3yrs,body fat percentage: 13.3±4.7%)volunteered to take part in two squat1 RM tests(free weight vs.Smith machine).The mean velocity(MV)of the subjects was measured during the test(using a linear position transducers)to derive the actual1 RM value.All repetitions of the squat 1RM test were performed at the subject’s maximum effort.After the test,the 5-point load method(relative load range:30%-85%)and the corresponding MV were selected to construct the individual’s load-velocity relationships in an Excel spreadsheet,and the mean velocity from the squat 1RM test was entered into the individual’s load-velocity relationships was used to calculate the predicted 1RM values.Pearson’s correlation coefficient(r),paired-samples t-test,and effect size(ES)size were used to test the correlation and difference between the predicted and actual values of 1RM.Results: The predicted value of 1RM predicted by the load-velocity relationships in free weight squat for the free weight squat was 170.0±41.0 kg,and the actual value was 146.8±23.5 kg,with statistically significant differences between the two data sets(t=-4.61,P<0.05,ES=1.12,95% CI: 0.50 to 1.72)and Pearson correlation coefficient r=0.93(P<0.05);the predicted value of Smith machine squat 1RM predicted by the load-velocity relationships in Smith machine squat was 168.0±32.2 kg,and the actual value was 162.8 ± 28.4 kg,with no statistically significant difference between the two data sets(t=-1.38,P=0.19,ES=0.33,95% CI: 0.16 to 0.82),and Pearson correlation coefficient r=0.88(P<0.05).The predicted value of free weight squat 1RM predicted by the load-velocity relationships in Smith machine squat was 154.1±35.7kg and the actual value was 146.8±23.5 kg,with no statistically significant difference between the two data sets(t=-1.32,P=0.20,ES=0.32,95% CI: 0.17 to 0.80)and Pearson correlation coefficient r=0.78(P<0.05);the predicted value predicted by the load-velocity relationships in free weight squat of the Smith machine squat 1RM was189.4 ± 50.8 kg,and the actual value was 162.8±28.4 kg,with a statistically significant difference between the two data sets(t=-4.00,P<0.05,ES=0.97,95% CI:0.38 to 1.54)and Pearson correlation coefficient r=0.91(P<0.05).Conclusions: 1)The validity of the load-velocity relationships to predict 1RM in Smith machine squat was better than that of the free weight squat.2)The validity of the Smith machine-based load-velocity relationships to predict 1RM in free weight squat is higher,and the validity of the free weight-based load-velocity relationships to predict 1RM in smith machine squat is less than ideal.Therefore 1RM measurements in squat for both weight-bearing modalities can be considered for estimation based on the load-velocity relationships constructed in Smith machine squat,but the load-velocity relationships constructed based on the free weight modality should be used with caution in squat 1RM measurements for both weight-bearing modalities. |
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